prof. Ing. Pavel Pechač, Ph.D.

Commercial Microwave Links for Urban Rainfall-runoff Modelling

Autoři: Fencl, M., Bareš, V., Pastorek, J., Ing. Martin Mudroch, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: RealPeP - Precipitation and Flash Flood Prediction from Minutes to Days. Berlin: European Meteorological Society, 2020.
Rok: 2020

Pracoviště: Katedra elektromagnetického pole
Anotace:
Urban catchments are characterized by diverse land cover with large ratio of impervious surfaces on which rainfall-runoff is generated extremely fast. This possess high requirements on spatio-temporal resolution of rainfall data needed for reliable runoff predictions. The contribution summarizes results from three-years experiment evaluating reliability of rainfall-runoff simulations at small urban catchment using rainfall observations from Commercial Microwave Links (CMLs). In addition, system for providing real-time CML-based rainfall product at city scale is presented. Finally, sustainability of the CML-based rainfall observation system is discussed with focus on challenges related to the fast development of communication networks.

Narrowband validation of a deterministic model in UAV scenarios

Autoři: Perez-Fontan, F., Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Kvičera, M., Gulie, I.
Publikace: 2019 13TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). IEEE (Institute of Electrical and Electronics Engineers), 2019. ISSN 2164-3342. ISBN 9788890701887.
Rok: 2019

Pracoviště: Katedra elektromagnetického pole
Anotace:
We present a partial validation of a deterministic tool initially oriented toward wideband satellite navigation channel modeling. Here, we try to reproduce the narrowband shadowing effects alone. The experimental setup corresponds to a low elevation link emulating the conditions encountered in UAV scenarios.

On Distance Factor in Rain Attenuation Predictions

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: 2019 13TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). IEEE (Institute of Electrical and Electronics Engineers), 2019. ISSN 2164-3342. ISBN 9788890701887.
Rok: 2019

Pracoviště: Katedra elektromagnetického pole
Anotace:
Comparison of rain attenuation prediction with measurements on commercial terrestrial microwave links at 25 GHz, 32 GHz and 38 GHz is presented. The comparison is done by means of cumulative probability distribution. Distance factor is included in the prediction to improve its accuracy. It is found that even with distance factor included, prediction systematically underestimates measured loss.

TEL4RAIN: MĚŘENÍ SRÁŽEK S VYSOKÝM ROZLIŠENÍM POMOCÍ TELEKOMUNIKAČNÍCH MIKROVLNNÝCH SPOJŮ

Autoři: Bareš, V., Fencl, M., Ing. Martin Mudroch, Ph.D., Stránský, D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Sborník přednášek a posterových sdělení. Brno: CzWA service, 2019. p. 337-344. ISSN 2694-7013.
Rok: 2019

Pracoviště: Katedra elektromagnetického pole
Anotace:
Projekt Tel4Rain řeší vývoj aplikace poskytující online data o srážkových intenzitách se zaměřením na hydrologii městských aglomerací s prostorovým rozlišením 500x500 m2 a časovým rozlišením 1 minuta. Projekt počítá s využitím přibližně 1000 mikrovlnných spojů na území hl.m. Prahy a okolí z telekomunikační sítě společnosti T-Mobile ČR. Data o útlumu signálu jsou získávána z páteřní sítě mikrovlnných spojů společnosti v reálném čase. Surová data jsou ukládána do PostgreSQL databáze a v hydrologickém modulu jsou přepočtena na srážkové intenzity. Modul prostorové rekonstrukce zahrnuje algoritmy, které informace z liniových spojů převádějí do pravidelné souřadnicové sítě s definovaným prostorovým rozlišením.

Analysis of Propagation of Electromagnetic Waves in Atmospheric Hydrometeors on Low-Elevation Paths

Autoři: Grábner, M., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: Radioengineering. 2018, 27(1), 29-33. ISSN 1210-2512.
Rok: 2018

DOI: 10.13164/re.2018.0029
Odkaz: https://doi.org/10.13164/re.2018.0029
Pracoviště: Katedra elektromagnetického pole
Anotace:
Attenuation of electromagnetic waves in millimeter wave bands is analyzed by means of experimental measurement of received signal fluctuations on terrestrial radio links operating in frequency bands 58, 94 and 122 GHz. Long-term time series of the received signal are processed to obtain annual and two-year cumulative distributions of attenuation due to hydrometeors. The measured statistics give the attenuation higher than predicted by the model of the Recommendation ITU-R P.530. Rain intensity measured simultaneously with rain attenuation is used to obtain fitted parameters of an attenuation/intensity power-law relationship. The empirical data extracted from the experiment are compared with the results of numerical simulations of attenuation due to rain and hailstones.

Comparison of Measured and Theoretically Predicted Rain Attenuation at 32 GHz and 38 GHz

Autoři: Valtr, P., Fencl, M., Bareš, V., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: 2018 12th European Conference on Antennas and Propagation. Bruxelles: The European Association on Antennas and Propagation, 2018. ISSN 0537-9989. ISBN 978-1-78561-815-4.
Rok: 2018

Pracoviště: Katedra elektromagnetického pole
Anotace:
Rain attenuation of terrestrial microwave links is addressed here. Statistics of attenuation from 17 short range links at frequency of 32 GHz and 38 GHz spanning over period of more than two years are shown. Statistics of measured attenuation is compared with theoretically calculated statistics of rain loss. Rainfall data used in theoretical calculations come from a network of rain gauges. It is found that theoretically calculated rain attenuation systematically underestimates measured loss by several dB.

Estimating wet antenna effect from long-term attenuation statistics of short commercial microwave links

Autoři: Fencl, M., Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Bareš, V.
Publikace: Geophysical Research Abstracts, Volume 18. Göttingen: Copernicus Publications, 2018.
Rok: 2018

Pracoviště: Katedra elektromagnetického pole
Anotace:
This contribution presents analysis of two years of data from eight short (48-497m) commercial microwave links operated at frequencies of 37.3-39.2 GHz within the cellular backhaul. WAA is quantified from the complementary cumulative distribution functions of measured attenuation, which is compared with theoretical ones calculated from rainfall data from nearby rain gauges. WAA dominates over path attenuation during light rainfalls (R < 2 mm/h) reaching 1.5-2.75 dB and increases for all eight links up to a probability level of 1 % (R <= 10 mm/h) reaching 3-5 dB. Maximal wet antenna attenuation observed during heavy rainfalls (R = 100-140 mm/h) at a 0.01 % probability level is between 5-12 dB. The WAA substantially contributes to total CML attenuation, especially by shorter CMLs. The results imply that wet antenna attenuation is dependent on rainfall intensity and increases exponentially towards a maximal value. The constant value of WAA used in previous studies may, therefore, lead to a significant underestimation of peak rainfalls. However, a wide range of estimated magnitudes during heavy rainfalls indicates that antenna wetting may also be dependent on other (unmeasured) environmental variables than rainfall as well as on antenna properties. Direct estimation of WAA from short links proposed in this study might, therefore, be convenient approach to account for WAA bias, especially when no reference rainfall data are available.

State Propagation Channel Model for 2 GHz UAV Links in Cluttered Environment

Autoři: Zelený, J., Kvičera, M., Valtr, P., Perez-Fontan, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: 2018 12th European Conference on Antennas and Propagation. Bruxelles: The European Association on Antennas and Propagation, 2018. ISSN 0537-9989. ISBN 978-1-78561-815-4.
Rok: 2018

Pracoviště: Katedra elektromagnetického pole
Anotace:
In civil surveillance applications, Unmanned Aerial Vehicles (UAVs) are being necreasingly used for emergency response or by law enforcement. Transferring enormous amount of data from UAV-mounted cameras or sensors requires significantly larger bandwidths compared to the command and control system. This results in the need of utilizing higher carrier frequencies, e.g. 2 GHz and above. As novel hardware development relies on underlying propagation channel models for the envisaged scenarios, which may range from deeply shadowed to line-of-sight, we focus here on obtaining and processing the relevant experimental datasets which enable us to develop or tune the particular models correctly. This paper studies three selected scenarios consisting of cluttered environment where individual propagation states of a Markov chain model are identified. The identification process of such states is described.

A New Model for Scattering From Tree Canopies Based on Physical Optics and Multiple Scattering Theory

Autoři: Kvičera, M., Peréz Fontán, F., Israel, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2017, 65(4), 1925-1933. ISSN 0018-926X.
Rok: 2017

DOI: 10.1109/TAP.2017.2669980
Odkaz: https://doi.org/10.1109/TAP.2017.2669980
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents a new model for scattering from tree canopies based on a modified physical optics approach. In this way, propagation through a canopy is accounted for by respecting the complex propagation constant, which can be obtained either by the multiple scattering theory (MST) or approximated based on the canopy specific attenuation. Unlike the case when MST is applied directly, the proposed approach offers significant benefits, including a straightforward software implementation, feasible computation times for high frequencies and electrically large canopies, and, most importantly, near-field calculations in regions close to a canopy. The new model is first tested against MST using two artificial single-tree scenarios at 2 and 10 GHz. Then, experimental data at 2 GHz obtained with the use of a remote controlled airship for an actual single-tree scenario are utilized as well. In this way, the model is thoroughly validated and its advantages over MST are presented in detail.

A New Propagation Channel Synthesizer for UAVs in the Presence of Tree Canopies

Autoři: Kvičera, M., Perez-Fontan, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Remote sensing. 2017, 9(2), ISSN 2072-4292.
Rok: 2017

DOI: 10.3390/rs9020151
Odkaz: https://doi.org/10.3390/rs9020151
Pracoviště: Katedra elektromagnetického pole
Anotace:
Following the increasing popularity of unmanned aerial vehicles (UAVs) for remote sensing applications, the reliable operation under a number of various radio wave propagation conditions is required. Assuming common outdoor scenarios, the presence of trees in the vicinity of a UAV or its ground terminal is highly probable. However, such a scenario is very difficult to address from a radio wave propagation point of view. Recently, an approach based on physical optics (PO) and the multiple scattering theory (MST) has been proposed by the authors, which enables fast and straightforward predictions of tree-scattered fields at microwave frequencies. In this paper, this approach is developed further into a generative model capable of providing both the narrowband and wideband synthetic time series of received/transmitted signals which are needed for both UAV communications and remote sensing applications in the presence of scattering from tree canopies. The proposed channel synthesizer is validated using both an artificially-generated scenario and actual experimental dataset.

Analysis of One-year Data of Slant Path Rain Attenuation at 19 and 39 GHz in Prague

Autoři: Grábner, M., Fišer, O., Pek, V., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: Proceedings of the European Conference on Antennas and Propagation. Piscataway, NJ: IEEE, 2017. p. 2361-2364. ISSN 2164-3342. ISBN 978-88-907018-7-0.
Rok: 2017

DOI: 10.23919/EuCAP.2017.7928593
Odkaz: https://doi.org/10.23919/EuCAP.2017.7928593
Pracoviště: Katedra elektromagnetického pole
Anotace:
Attenuation time series measured on the satellite-to-ground path in Prague in frequency bands 19 and 39 GHz and simultaneously measured rain intensity are analyzed statistically using one-year dataset. Frequency scaling is described by linear models. Empirical power law models are fitted to the measured data directly and to the obtained annual cumulative distributions. Monthly statistics obtained shows the worst months in terms of rain attenuation. Fade slope and fade duration cumulative distributions are determined and discussed.

On Horizontal Distribution of Vertical Gradient of Atmospheric Refractivity

Autoři: Grábner, M., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: Atmospheric Science Letters. 2017, 18 294-299. ISSN 1530-261X.
Rok: 2017

DOI: 10.1002/asl.755
Odkaz: https://doi.org/10.1002/asl.755
Pracoviště: Katedra elektromagnetického pole
Anotace:
The horizontal distribution of the vertical gradient of atmospheric refractivity is important for the assessment of the propagation of electromagnetic waves on nearly horizontal paths. A 5-year set of meteorological data, obtained fromthe ERA-Interim numerical weather product, has been used to analyze this distribution statistically. Vertical gradient maps of the Central European region have been processed to derive empirical probability distributions of the difference between local point gradient values at two locations. The difference of the effective (path-averaged) gradient along the path and the local gradient is shown to be statistically distributed so that the quantiles increase linearly with distance in the interval from 100 to 1000 km. Finally, a spatial correlation function is obtained and described by an exponential model with correlation distances determined in the range of 400–700 km.

Open area 2 x 2 MIMO channel model for 2 GHz low-elevation links with diversity and capacity applications

Autoři: Zelený, J., Perez-Fountan, F., prof. Ing. Pavel Pechač, Ph.D., Marion-Espineira, P.
Publikace: Radio Science. 2017, 55(5), 616-629. ISSN 0048-6604.
Rok: 2017

DOI: 10.1002/2016RS006199
Odkaz: https://doi.org/10.1002/2016RS006199
Pracoviště: Katedra elektromagnetického pole
Anotace:
In civil surveillance applications, unmanned aerial vehicles (UAV) are being increasingly used in floods, fires, and law enforcement scenarios. In order to transfer large amounts of information from UAV-mounted cameras, relays, or sensors, large bandwidths are needed in comparison to those required for remotely commanding the UAV. This demands the use of higher-frequency bands, in all probability in the vicinity of 2 or 5 GHz. Novel hardware developments need propagation channel models for the ample range of operational scenarios envisaged, including multiple-input, multiple-output (MIMO) deployments. These configurations may enable a more robust transmission by increasing either the carrier-to-noise ratio statistics or the achievable capacity. In this paper, a 2 x 2 MIMO propagation channel model for an open-field environment capable of synthesizing a narrowband time series at 2 GHz is described. Maximal ratio combining diversity and capacity improvements are also evaluated through synthetic series and compared with measurement results. A simple flat, open scenario was evaluated based on which other, more complex environments can be modeled.

Water Vapor Density Profile Statistics in the Atmospheric Boundary Layer

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Grábner, M.
Publikace: Proceedings of the European Conference on Antennas and Propagation. Piscataway, NJ: IEEE, 2017. p. 2093-2095. ISSN 2164-3342. ISBN 978-88-907018-7-0.
Rok: 2017

DOI: 10.23919/EuCAP.2017.7928173
Odkaz: https://doi.org/10.23919/EuCAP.2017.7928173
Pracoviště: Katedra elektromagnetického pole
Anotace:
One year statistics of water vapor density is presented. Measured data presented were obtained using meteorological sensors mounted on a mast, thus having very good height and temporal resolution. Measurement results are in the form of surface water vapor density and water vapor density gradient. Results of measurement data analysis are compared with values recommended by ITU-R.

A Model for the Detailed Analysis of Radio Links Involving Tree Canopies

Autoři: Perez-Fontan, F., Kvičera, M., prof. Ing. Pavel Pechač, Ph.D., Israel, J.
Publikace: Radioengineering. 2016, 25(4), 637-643. ISSN 1210-2512.
Rok: 2016

DOI: 10.13164/re.2016.0637
Odkaz: https://doi.org/10.13164/re.2016.0637
Pracoviště: Katedra elektromagnetického pole
Anotace:
Detailed analysis of tree canopy interaction with incident radiowaves has mainly been limited to remote sensing for the purpose of forest classification among many other applications. This represents a monostatic configuration, unlike the case of communication links, which are bistatic. In general, link analyses have been limited to the application of simple, empirical formulas based on the use of specific attenuation values in dB/m and the traversed vegetated mass as, e.g., the model in Recommendation ITU-R P.833-8 [1]. In remote sensing, two main techniques are used: Multiple Scattering Theory (MST) [25] and Radiative Transfer Theory (RT), [5], [6]. We have paid attention in the past to MST [710]. It was shown that a full application of MST leads to very long computation times which are unacceptable in the case where we have to analyze a scenario with several trees. Extensive work using MST has been also presented by others in [1116] showing the interest in this technique. We have proposed a simplified model for scattering from tree canopies based on a hybridization of MST and a modified physical optics (PO) approach [16]. We assume that propagation through a canopy is accounted for by using the complex valued propagation constant obtained by MST. Unlike the case when the full MST is applied, the proposed approach offers significant benefits including a direct software implementation and acceptable computation times even for high frequencies and electrically large canopies. The proposed model thus replaces the coherent component in MST, significant in the forward direction, but keeps the incoherent or diffuse scattering component present in all directions. The incoherent component can be calculated within reasonable times. Here, we present tests of the proposed model against MST using an artificial single-tree scenario at 2 GHz and 10 GHz.

Attenuation due to hydrometeors in three millimeter wave bands

Autoři: Grábner, M., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: 2016 10th European Conference on Antennas and Propagation. Bruxelles: The European Association on Antennas and Propagation, 2016. pp. 1-4. ISSN 2164-3342. ISBN 978-88-907018-6-3.
Rok: 2016

DOI: 10.1109/EuCAP.2016.7481331
Odkaz: https://doi.org/10.1109/EuCAP.2016.7481331
Pracoviště: Katedra elektromagnetického pole
Anotace:
Attenuation due to atmospheric hydrometeors is measured simultaneously on experimental terrestrial radio links operating at millimeter-wave frequency bands 58, 94 and 122 GHz. Attenuation events observed during a period from May 2013 to April 2014 are analyzed statistically to obtain monthly cumulative distributions as well as worst month and annual statistics of attenuation. The frequency bands 94 and 122 GHz suffer from slightly higher attenuation than the 58 GHz band but the difference between 94 and 122 GHz is relatively small.

Clutter Loss Modelling for Low Elevation Link Scenarios

Autoři: Valtr, P., Zelený, J., prof. Ing. Pavel Pechač, Ph.D., Grábner, M.
Publikace: International Journal of Antennas and Propagation. 2016, 2016 ISSN 1687-5869.
Rok: 2016

DOI: 10.1155/2016/1478471
Odkaz: https://doi.org/10.1155/2016/1478471
Pracoviště: Katedra elektromagnetického pole
Anotace:
An analysis of the accuracy of several deterministic and semideterministic propagation models related to calculating clutter loss for low elevation links is presented. Predictions are compared with measurements carried out at 2GHz over three locations. By comparing prediction and measurement techniques, improved predictive capabilities of deterministic models are demonstrated and quantified in cases where a description of the propagation environment exists and an air-to-ground scenario is considered.

Inverse Gaussian-based composite channel model and time series generator for land mobile satellite systems under tree shadowing

Autoři: Kourogiorgas, C., Kvičera, M., Panagopoulos, A. D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IET Microwaves, Antennas & Propagation. 2016, 10(6), 612-616. ISSN 1751-8725.
Rok: 2016

DOI: 10.1049/iet-map.2015.0725
Odkaz: https://doi.org/10.1049/iet-map.2015.0725
Pracoviště: Katedra elektromagnetického pole
Anotace:
In this study, a new composite channel model for land mobile satellite (LMS) systems under tree shadowing is proposed utilising the inverse Gaussian (IG) distribution to model the shadowing component. Using the experimental data of received power under tree shadowing at L-band, which were carried out at Stromovka Park in Prague, the Czech Republic, the assumption of the IG distribution for the description of the first-order statistics of large-scale effects is investigated and validated. A new LMS channel model is developed as a sum of a signal experiencing IG shadowing and a signal under Rayleigh multipath effects. Moreover, a methodology to generate accurate time series of the received signal envelope using the IG distribution is presented. Such methodology and generally time series generators can be used for the evaluation of system’s performance and for end-to-end simulations. Finally, it is shown that the proposed time series generator reproduces the first-order and second-order statistics of the LMS channel model with a very good accuracy.

Modeling scattering from tree canopies for UAV scenarios

Autoři: Kvičera, M., Pérez-Fontán, Fernando, Israel, Jonathan, prof. Ing. Pavel Pechač, Ph.D.,
Publikace: 2016 10th European Conference on Antennas and Propagation. Bruxelles: The European Association on Antennas and Propagation, 2016. pp. 1-3. ISSN 2164-3342. ISBN 978-88-907018-6-3.
Rok: 2016

DOI: 10.1109/EuCAP.2016.7481249
Odkaz: https://doi.org/10.1109/EuCAP.2016.7481249
Pracoviště: Katedra elektromagnetického pole
Anotace:
Unmanned aerial vehicles (UAVs) can generally operate under very different conditions from a radiowave propagation point of view. This also includes scenarios where the presence of vegetation can be in a close vicinity of the UAV or its ground control station. Treating the interaction of electromagnetic waves and vegetation has always been of great interest and thus, so far, different approaches have been developed. Here we provide a basic background and a comparison with experimental data for the case of the multiple scattering theory approach (recently adopted in the latest version of Recommendation ITU-R P.833) and the physical optics approach. In addition, based on the model currently being developed, the possibilities to overcome the great computation demands of the multiple scattering theory are outlined as well.

Sensitivity Analysis of Multiple Scattering Theory Applied to Tree Canopies at Microwave Frequencies

Autoři: Kvičera, M., Israel, Jonathan, Perez-Fontan, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Antennas and Wireless Propagation Letters. 2016, 15 1175-1178. ISSN 1536-1225.
Rok: 2016

DOI: 10.1109/LAWP.2015.2498645
Odkaz: https://doi.org/10.1109/LAWP.2015.2498645
Pracoviště: Katedra elektromagnetického pole
Anotace:
A sensitivity analysis of the multiple scattering theory applied to propagation in tree canopies is presented. This analysis aims at addressing the influence of input parameters on the canopy’s equivalent scattering amplitude as well as the overall coherent and incoherent scattered fields. The main input parameters of interest were identified as frequency, number densities and dielectric parameters of branches and leaves, polarization and a canopy shape. A number of graphical results are provided enabling to identify the key parameters of corresponding radiowave propagation models based on the multiple scattering theory.

A Mode-Matching Technique for Analysis of Scattering by Periodic Comb Surfaces

Autoři: Valtr, P., Davenport, Ch.J., prof. Ing. Pavel Pechač, Ph.D., Rigelsford, J.M.
Publikace: IEEE Transactions on Antennas and Propagation. 2015, 63(9), 4016-4023. ISSN 0018-926X.
Rok: 2015

DOI: 10.1109/TAP.2015.2452945
Odkaz: https://doi.org/10.1109/TAP.2015.2452945
Pracoviště: Katedra elektromagnetického pole
Anotace:
Numerical techniques for calculating electromagnetic fields within three-dimensional surfaces are computationally intensive. Therefore, this paper presents the application of a modematching technique developed for analyzing electromagnetic scattering from periodic comb surfaces illuminated by a plane wave. A set of linear equations has been developed to calculate mode coefficients of the field distribution for both E- and H-polarized incident waves. Analysis is performed for two cases where the comb thickness is either infinitely thin or of a finite thickness. The technique is shown to accurately predict both field intensities within the near-field of the periodic surface and far-field scattering patterns. Results are compared to those obtained using the finite integration techniques (FIT) implemented in CST Microwave Studio. Furthermore, numerical results are compared to measurements of an aluminum prototype. Additional far-field scattering measurements using a bi-static system provide additional confidence in CST simulations and the mode-matching methods presented here.

Experimental Study on Terrestrial Links Enhancement at 11 and 38 GHz

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D., Grábner, M., Valtr, P., Kvičera, V., Martellucci, A.
Publikace: IEEE Transactions on Antennas and Propagation. 2015, 63(7), 3179-3186. ISSN 0018-926X.
Rok: 2015

DOI: 10.1109/TAP.2015.2421940
Odkaz: https://doi.org/10.1109/TAP.2015.2421940
Pracoviště: Katedra elektromagnetického pole
Anotace:
A detailed analysis of 1-year, long-term experimental measurements of signal enhancement at a terrestrial link between two cities in the Czech Republic is presented with respect to an interference and frequency coordination analysis based on recommendation ITU-R P.452-14. Three different models for terrain diffraction are considered to demonstrate a significant influence on signal enhancement predictions. The impact of radiometeorological parameters, serving as inputs for recommendation ITU-R P.452-14, was addressed by utilizing available ITU-R and ERAInterim maps, or, their locally obtained values. Monthly and seasonal variations are discussed in addition to the 1-year signal enhancement statistics.

First-Order Statistics Prediction for a Propagation Channel of Arbitrary Non-Geostationary Satellite Orbits

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2015, 1(24), 93-97. ISSN 1210-2512.
Rok: 2015

DOI: 10.13164/re.2015.0093
Odkaz: https://doi.org/10.13164/re.2015.0093
Pracoviště: Katedra elektromagnetického pole
Anotace:
A method enabling the prediction of the firstorder statistics of received signal levels for arbitrary nongeostationary satellite orbits based on a reference dataset for a wide range of elevation angles is introduced for azimuth- independent scenarios and high elevation angles. The method is further validated by experimental data obtained during measurements with a remote-controlled airship utilized as a pseudo-satellite. These experimental trials were performed at a frequency of 2.0 GHz at two scenarios at Stromovka Park in Prague, Czech Republic, in August 2013 and March 2014. An excellent match between the predicted and actual cumulative distribution functions of received signal levels was identified for both scenarios.

Generalized Propagation Channel Model for 2GHz Low Elevation Links Using a Ray-tracing Method

Autoři: Zelený, J., Perez-Fontan, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2015, 24(4), 1044-1049. ISSN 1210-2512.
Rok: 2015

DOI: 10.13164/re.2015.1044
Odkaz: https://doi.org/10.13164/re.2015.1044
Pracoviště: Katedra elektromagnetického pole
Anotace:
Unmanned Aerial Vehicles (UAV) will increasingly be used for responding to emergencies or for law enforcement in civil surveillance applications. Transferring the enormous amounts of information from UAV-mounted cameras or sensors will require large bandwidths, unlike the information required for remotely controlling a UAV, thus necessitating higher frequency bands typically in the vicinity of 2 or 5 GHz. Novel hardware developments will need to rely on a versatile propagation channel model for the envisaged scenarios ranging from deep shadow urban areas to open fields. This paper studies more complex intermediate scenarios, which fall between the aforementioned ones, and which are more difficult to model. A semideterministic model, first developed for open, flat areas, has been generalized to accommodate any possible operational scenario and was tested in built-up areas. The model involves a stochastic part and a determinist which is a raytracing based part used to compute the long term mean (LTM) of the signal's coherent component.

Inclusion of Higher Order Diffracted Fields in the Epstein-Peterson Method

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Grábner, M.
Publikace: IEEE Transactions on Antennas and Propagation. 2015, 63(7), 3240-3244. ISSN 0018-926X.
Rok: 2015

DOI: 10.1109/TAP.2015.2421949
Odkaz: https://doi.org/10.1109/TAP.2015.2421949
Pracoviště: Katedra elektromagnetického pole
Anotace:
A higher order diffracted field calculation to improve the accuracy of a multiple screen diffraction scenario analysis is discussed. In particular, this communication addresses and investigates the accuracy of the Epstein–Peterson prediction method based on the order of the diffracted field used. Theoretical results are compared with diffraction loss measurements, derived from a set of terrain profiles, to demonstrate how the inclusion of the higher order diffracted field significantly improves the accuracy of the Epstein–Peterson method predictions.

Influence of Input Terrain Profile Resolution on Diffraction Modeling

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D., Valtr, P., Ing. Tomáš Kořínek, Ph.D., Kvičera, M., Grábner, M., Martellucci, A.
Publikace: IEEE Antennas and Wireless Propagation Letters. 2015, 13 1318-1321. ISSN 1536-1225.
Rok: 2015

DOI: 10.1109/LAWP.2015.2403867
Odkaz: https://doi.org/10.1109/LAWP.2015.2403867
Pracoviště: Katedra elektromagnetického pole
Anotace:
Tests using three selected terrain diffraction models, three available experimental datasets and three digital elevation products with different horizontal and vertical resolutions were carried out to assess the role of input terrain profile in diffraction modeling. It is demonstrated that low-resolution terrain maps are not, generally speaking, suitable for terrain diffraction modeling. Further, it is also shown that utilizing digital elevation products with medium spatial resolution results in predictions close to the case when high-resolution terrain maps are considered. Index Terms—Digital elevation products, modeling, propagation,

Initial Results from a Measurement Campaign for Low Elevation Angle Links in Different Environments

Autoři: Zelený, J., Pérez-Fontan, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 9th European Conference on Antennas and Propagation (EUCAP 2015). Piscataway: IEEE, 2015. ISBN 978-88-907018-5-6.
Rok: 2015

Pracoviště: Katedra elektromagnetického pole
Anotace:
Unmanned aerial vehicles (UAV) are widely used in civil applications nowadays and resulting photomaps, or aerial monitoring, demand an enormous amount of transmitted data in high frequency links. In the new generation of wireless communication standards, different propagation channel models are recommended for system simulations to develop new hardware. Every channel model needs to be validated by experimental measurement data, from pre-defined scenarios such as urban, suburban, remote or isolated housing estate, open field and vegetation covered area. As reliable data harvesting is a key issue, a low cost measurement campaign is being developed.

Measurements of Horizontal Variations of Radio Refractivity - First Results

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Grábner, M.
Publikace: Proceedings of the 9th European Conference on Antennas and Propagation (EUCAP 2015). Piscataway: IEEE, 2015. ISBN 978-88-907018-5-6.
Rok: 2015

Pracoviště: Katedra elektromagnetického pole
Anotace:
Horizontal variation of radio refractivity is addressed. A measurement campaign was performed by means of a remote controlled airship carrying sensors of temperature, pressure and humidity. The measurement was done over a 13 km long horizontal path at various heights. The path was partly over land and partly over water. The measurements show change of refractivity along the path caused mainly by change of relative humidity of air. Horizontal refractivity gradients calculated range between 0.75 N/km and 2 N/km.

Scattering from Single Isolated Tree Based on Physical Optics: Preliminary Model

Autoři: Kvičera, M., Pérez-Fountán, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 9th European Conference on Antennas and Propagation (EUCAP 2015). Piscataway: IEEE, 2015. ISBN 978-88-907018-5-6.
Rok: 2015

Pracoviště: Katedra elektromagnetického pole
Anotace:
A model for single tree scattering is being developed. The model is to be validated by measurements performed at 2 GHz with the use of a remote-controlled airship in the area of Prague, the Czech Republic. The first level of the model, accounting for the trunk and main branches, is based on Physical Optics techniques applied to dielectrics and is presented in this paper and compared with one set of experimental data. The model will be completed with the inclusion of the contributions, coherent and incoherent, of the leafy canopy. As the work is still ongoing, only the preliminary results are shown.

Seasonal Variations of Polarization Diversity Gain in a Vegetated Area considering High Elevation Angles and a Nomadic User

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: International Journal of Antennas and Propagation. 2015, 2015(2015), 1-9. ISSN 1687-5869.
Rok: 2015

DOI: 10.1155/2015/194626
Odkaz: https://doi.org/10.1155/2015/194626
Pracoviště: Katedra elektromagnetického pole
Anotace:
Seasonal variations of the polarization diversity gain are addressed for a nomadic user in a vegetated area taking high elevation angles and nongeostationary satellites into consideration.Corresponding experimental datawere obtained at a frequency of 2.0GHz at Stromovka Park in Prague, the Czech Republic, within the full in-leaf and out-of-leaf periods of 2013 and 2014, respectively. By detecting copolarized and cross-polarized components of the transmitted left- and right-handed circularly polarized signals, the corresponding diversity gain was obtained for multiple-input single-output (MISO), single-input multiple-output (SIMO), and combined MISO/SIMO cases. It was found that tree defoliation results in a significant decrease of the polarization diversity gain achieved for low time percentages in particular scenarios.

Spatial Correlation of Vertical Gradient of Refractivity on Large Scales

Autoři: Grábner, M., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: Proceedings of the 9th European Conference on Antennas and Propagation (EUCAP 2015). Piscataway: IEEE, 2015. ISBN 978-88-907018-5-6.
Rok: 2015

Pracoviště: Katedra elektromagnetického pole
Anotace:
Spatial distribution maps of the vertical gradient of atmospheric refractivity are derived from a global dataset of meteorological quantities as given by ERA-Interim reanalysis. Spatial correlation of the gradient on large scales is analyzed using data from the European region. The examples of time evolution of the gradient fields are presented and spatial correlation characteristics obtained are discussed. Index Terms—tropospheric propagation, atmospheric refractivity, refractivity gradient, spatial correlation.

Advanced Modelling of Intelligent Walls for Indoor Smart Environments

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D., Vallecchi, A., Ford, L., Langley, R., Rigelsford, J.
Publikace: Conference Proceedings of EuCAP 2014. Bruxelles: The European Association on Antennas and Propagation, 2014. pp. 620-622. ISBN 978-88-907018-4-9.
Rok: 2014

DOI: 10.1109/EuCAP.2014.6901835
Odkaz: https://doi.org/10.1109/EuCAP.2014.6901835
Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper deals with the modelling of Intelligent Walls, i.e. building walls that are capable of providing real time control of propagation in indoor environments. The Intelligent Wall is a metalized wall equipped with an Intelligent Wall Unit allowing the wall to change its electromagnetic properties in real time. The wall parameters are pre-calculated using CST Microwave Studio and then employed in a radio-wave propagation model based on the modified Ray-Launching method. The crucial part of the algorithm, the interaction between a ray and an Intelligent Wall is explained in detail. The structure of the Intelligent Wall Unit is briefly described and coverage calculations in a sample scenario are presented.

First Results of Concurrent Rain Attenuation Measurement in Three Millimeter Wave Bands

Autoři: Grábner, P., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: Proceedings of 31st URSI GASS. Piscataway: IEEE, 2014. ISBN 978-1-4673-5225-3.
Rok: 2014

DOI: 10.1109/URSIGASS.2014.6929689
Odkaz: https://doi.org/10.1109/URSIGASS.2014.6929689
Pracoviště: Katedra elektromagnetického pole
Anotace:
Rain attenuation is measured on experimental millimeter wave terrestrial paths operating in three frequency bands 58, 94 and 122 GHz. Rain intensity is measured continuously at the receiver site. Several recorded rain attenuation events are analyzed and the power law relationship between the rain intensity and rain attenuation is tested in the three frequency bands. It is observed that frequency 122 GHz is not significantly more attenuated in rain than frequency 94 GHz.

Frequency Selective Building Facades

Autoři: Valtr, P., Yu, T., Zhao, W., prof. Ing. Pavel Pechač, Ph.D., Altan, H., Ford, L.
Publikace: Conference Proceedings of EuCAP 2014. Bruxelles: The European Association on Antennas and Propagation, 2014. pp. 623-624. ISBN 978-88-907018-4-9.
Rok: 2014

DOI: 10.1109/EuCAP.2014.6901836
Odkaz: https://doi.org/10.1109/EuCAP.2014.6901836
Pracoviště: Katedra elektromagnetického pole
Anotace:
In-building propagation of electromagnetic waves is addressed. Signal strength within buildings is influenced by various propagation mechanisms depending on building construction and material, and other architectural features. Nowadays buildings with green facades, i.e. plants attached to it are becoming popular. Another feature of buildings and building facades are window blinds, and other parallel plate waveguidelike structures. This paper is focused on transmission properties of a green facade and parallel plate waveguide array. The purpose of this paper is to present a simple approach of calculating field transmission through such structures with application to ray-based propagation tools for outdoor-to-indoor propagation prediction.

Modeling of First-Order Statistics of LMS Channel under Tree Shadowing for Various Elevation Angles at L-Band

Autoři: Kourogiorgas, Ch. I., Kvičera, M., Skraparlis, D., Ing. Tomáš Kořínek, Ph.D., Sakarellos, V. K,, Panagopoulos, A. D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Conference Proceedings of EuCAP 2014. Bruxelles: The European Association on Antennas and Propagation, 2014. pp. 2273-2277. ISBN 978-88-907018-4-9.
Rok: 2014

DOI: 10.1109/EuCAP.2014.6902267
Odkaz: https://doi.org/10.1109/EuCAP.2014.6902267
Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper, the first order statistics of co-polar components for a Land Mobile Satellite (LMS) channel for two scenarios, are investigated. The two scenarios refer to tree shadowing, one with the receiver placed inside an alley of trees and the second one with the receiver placed outside this alley of trees. For these two scenarios the received power for two orthogonal co-polar components was measured at Stromovka Park of Czech Republic using an airship. Due to the significance of first-order statistics of the signal envelope, using the measured power, four distributions are evaluated. More particularly, the Loo, Rice, Rayleigh and Lognormal distributions are investigated for modelling the Cumulative Distribution Function of the signal envelope for various elevation angles. It is found that Rice and Loo distributions have a very similar behaviour, while Rayleigh has the worst performance. Finally, some useful conclusions are drawn.

Modeling of First-Order Statistics of the MIMO Dual Polarized Channel at 2 GHz for Land Mobile Satellite Systems under Tree Shadowing

Autoři: Kourogiorgas, C., Kvičera, M., Skraparlis, D., Ing. Tomáš Kořínek, Ph.D., Sakarellos, V,, Panagopoulos, A. D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2014, 62(10), 5410-5415. ISSN 0018-926X.
Rok: 2014

DOI: 10.1109/TAP.2014.2346186
Odkaz: https://doi.org/10.1109/TAP.2014.2346186
Pracoviště: Katedra elektromagnetického pole
Anotace:
The Land Mobile Satellite (LMS) channel at 2GHz is examined and the first order statistics are modeled using experimental data for two tree shadowing scenarios. Considering that the first order statistics of the channel are used as input to channel models as well as for the calculation of the system margins, the modeling of the Probability Density Function (PDF) and the Cumulative Distribution Function (CDF) of the received signal envelope is of great importance for the design of LMS systems. Experimental data from measurements performed in Prague, the Czech Republic, are presented for two scenarios, a Heavy Tree Shadowing one and an Intermediate Tree Shadowing one. Four of the most widely used distributions, Rayleigh, Rice, Loo and lognormal, are considered for the modeling of the CDF of the signal envelope. Loo and Rice distributions out of the four considered distributions provide the best fit with reference to the measured data. Moreover, analytical empirical expressions are given for the parameters of the Loo distributions as a function of the elevation angle, to be used for the modeling of the LMS channel under tree shadowing. It is found that the expressions for the estimation of the distributions’ parameters provide a good fit to the experimental data.

Novel Mobility Model for Indoor Conference Scenarios

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D., Hrstka, O., Micka, V., doc. Ing. Jiří Vokřínek, Ph.D.,
Publikace: Conference Proceedings of EuCAP 2014. Bruxelles: The European Association on Antennas and Propagation, 2014. p. 2136-2137. ISBN 978-88-907018-4-9.
Rok: 2014

DOI: 10.1109/EuCAP.2014.6902231
Odkaz: https://doi.org/10.1109/EuCAP.2014.6902231
Pracoviště: Katedra elektromagnetického pole, Katedra počítačů
Anotace:
This paper introduces a novel mobility model for indoor conference scenarios. A multi-agent event-based simulator for evaluation of crowd behavior is used for users’ movement modelling inside a conference scenario. The radiowave propagation calculation is performed using a 3D semideterministic propagation model. Based on the two inputs, it is shown that users’ behavior needs to be taken into account when designing a new wireless network. If not, some of the access points can be overloaded for most of the time, while the rest can remain idle despite the fact that they provide satisfactory coverage in the entire scenario.

Short-Term Terrain Diffraction Measurements From L- to Q-Band: Results and Analysis

Autoři: Kvičera, M., Ing. Tomáš Kořínek, Ph.D., Kvičera, V,, Grábner, M., Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Martellucci, A.
Publikace: IEEE Transactions on Antennas and Propagation. 2014, 7(62), 3693-3701. ISSN 0018-926X.
Rok: 2014

DOI: 10.1109/TAP.2014.2316283
Odkaz: https://doi.org/10.1109/TAP.2014.2316283
Pracoviště: Katedra elektromagnetického pole
Anotace:
In response to the current need for a reliable interference and frequency coordination analysis, especially within the ground segment of satellite systems, atmospheric refraction and terrain diffraction phenomena play a key role from a radiowave propagation point of view. While it is convenient to use an ITU-R model for the case of the atmospheric refraction, several different types of models for terrain diffraction are identified in the literature. On the other hand, only a limited amount of experimental data is globally available to address their performance. This is why we carried out own short-term terrain diffraction measurements at the frequencies from L- to Q-band. During the trials, truck-mounted access platforms reaching up to 46 m above ground level were used and terrain profiles with path lengths from 7 km up to 50 km for various combinations of transmitter and receiver heights were addressed. Based on the obtained experimental dataset, the performance of the delta-Bullington and Deygout models, currently recommended by the ITU-R for the purposes of interference analysis, and the terrain diffraction models based on the UTD and parabolic equation approach has been addressed in terms of the testing variable defined in this paper.

World Maps of Atmospheric Refractivity Statistics

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Kvičera, M., Valtr, P., Martellucci, A.
Publikace: IEEE Transactions on Antennas and Propagation. 2014, 7(62), 3714-3722. ISSN 0018-926X.
Rok: 2014

DOI: 10.1109/TAP.2014.2317474
Odkaz: https://doi.org/10.1109/TAP.2014.2317474
Pracoviště: Katedra elektromagnetického pole
Anotace:
Atmospheric refractivity and its vertical gradient affect electromagnetic wave propagation in the atmosphere. Consequently, their statistics are needed for propagation predictions. New world maps of refractivity and its vertical gradient statistics are derived from a global, long-term dataset of meteorological quantities as given by ERA-Interim reanalysis. The derived maps provide long-term statistics obtained from 33 years of meteorological data with a one-degree spatial resolution on a latitude/longitude mesh. A processing method is described and examples of the derived maps are shown. The consistency of the new maps is checked by comparing world maps provided by ITU-R. Accuracy is tested by comparing refractivity statistics obtained from high-quality local measurements using radiosonde and tower measurements. New global maps demonstrate enhanced statistical stability, spatial resolution, and accuracy.

Atmospheric Refractivity Profiles and Microwave Propagation on a Terrestrial Path - Experiment and Simulation

Autoři: Grabner, M., Kvicera, V., prof. Ing. Pavel Pechač, Ph.D., Valtr, P., Jícha, O.
Publikace: Proceedings of 13th Conference on Microwave Techniques COMITE 2013. Pardubice: Univerzita Pardubice, 2013. pp. 11-15. ISBN 978-1-4673-5513-1.
Rok: 2013

DOI: 10.1109/COMITE.2013.6545035
Odkaz: https://doi.org/10.1109/COMITE.2013.6545035
Pracoviště: Katedra elektromagnetického pole
Anotace:
The results of experimental measurement of atmospheric refractivity profiels and microwave propagation characteristics at 11 GHz carried out recently at the Podebrady site in the Czech Republic are presented. Long term statistics of atmospheric refractivity were obtained from the tower measurement of tepmerature, pressure and relative humidity of air. Microwave propagation during clear air conditions was observed concurrently on the 50 km long terrestrial path Prague-Podebrady with several receivers located in different heights above the ground. Propagation of eletromagnetic waves was modled using the parabolic equation method and compared with measured data.

Closed-Form Approximation for Parallel-Plate Waveguide Coefficients

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2013, 22(4), 1296-1300. ISSN 1210-2512.
Rok: 2013

Pracoviště: Katedra elektromagnetického pole
Anotace:
Simple closed-form formulas for calculating coefficients of modes excited in a parallel-plate waveguide illuminated by a planar wave are presented. The mode-matching technique and Green’s formula are used to arrive at a matrix-based expression for waveguide coefficients calculation. Simplified solution to this matrix is proposed to derive approximate mode coefficient formulas in closed-form for both TE and TM polarization. The results are validated by numerical simulations and show good accuracy for all incidence angles and in broad frequency range.

Controlling Coverage for Indoor Wireless Networks Using Metalized Active FSS Walls

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D., Ford, L., Langley, R., Rigelsford, J.
Publikace: Proceedings of the19th Asia-Pacific Conference on Communications (APCC 2013). IEEE, 2013. p. 496-500. ISSN 2163-0771. ISBN 978-1-4673-6050-0.
Rok: 2013

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents a concept of an advanced method of controlling coverage for indoor wireless networks. The concept is based on the fact that electromagnetic wave propagation in indoor scenarios is mainly influenced by the propagation environment, e. g. walls, floors, ceilings, furniture etc. and such a propagation environment can be adjusted dynamically according to the current demands of the network by deploying what we call Active Frequency Selective Surface (AFFS) Walls. Using these walls, we are able to control the signal propagation at various frequencies, control the shape of covered area and limit interference. An example two-storey scenario acting as a small conference center is presented. The concept is verified by simulating simple Wi-Fi network and system of AFSS Walls. Advantages as well as potential problems of the proposed concept are discussed.

EM Wave Transmission through a Window Blind Structure

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC). Piscataway: IEEE, 2013. pp. 472-474. ISBN 978-1-4673-5689-3.
Rok: 2013

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with effects of window blinds on indoor propagation of electromagnetic waves. Measurement results of insertion loss due to window blind structure are presented for various orientations of window blind lamellas.

Estimation of the Radio Refractivity Gradient From Diffraction Loss Measurements

Autoři: Jícha, O., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: IEEE Transactions on Geoscience and Remote Sensing. 2013, 51(1), 12-18. ISSN 0196-2892.
Rok: 2013

DOI: 10.1109/TGRS.2012.2199995
Odkaz: https://doi.org/10.1109/TGRS.2012.2199995
Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to show that the gradient of the vertical radio refractivity profile of air near the ground can be estimated from measurements of electromagnetic wave strength. Diffraction can be used as the basic physical principle for non-line-of-sight radio links, where an obstacle covers some parts of the Fresnel zones, and therefore, the strength of electromagnetic wave is proportional to the ratio of coverage. The method, which is simple and easy to implement, is verified by measured data, and comparisons with meteorological measurements are presented.

Feasibility of UAV Link Space Diversity in Wooded Areas

Autoři: Šimůnek, M., prof. Ing. Pavel Pechač, Ph.D., Fontan, F. P.
Publikace: International Journal of Antennas and Propagation. 2013, 2013(2013), ISSN 1687-5869.
Rok: 2013

DOI: 10.1155/2013/890629
Odkaz: https://doi.org/10.1155/2013/890629
Pracoviště: Katedra elektromagnetického pole
Anotace:
Space diversity techniques provide an effective way to mitigate the deep fades in received power in a scattering environment. Space diversity influence on narrowband UAV links, which are unique due to the elevation angle and mutual position of a moving transmitter in homogeneous environment and static receiver in scattering environment, is analyzed in a wooded area using a remotely controlled airship at 2GHz. The experimental link forms a 1x4 SIMO configuration with influence quantified by values of diversity gain and subsequent comparison with Rayleigh fading series. The mutual antenna distance and elevation angle influence is also studied as the difference between the wooded area and an open field or urban environment.

Measurement of Window Blind Attenuation at 5-50 GHz

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Ing. Tomáš Kořínek, Ph.D., Morávek, O., Příhoda, M.
Publikace: Proceedings of the 7th European Conference on Antennas and Propagation (EUCAP 2013). Piscataway: IEEE, 2013. pp. 3653-3656. ISBN 978-88-907018-3-2.
Rok: 2013

Pracoviště: Katedra elektromagnetického pole
Anotace:
Effects of window blind with metal-lamellas on radiowave propagation are addressed. Measurements of insertion loss at frequency range 5 - 50 GHz are presented. The measurements were done for various inclinations of lamellas of the window blind structure for both vertical and horizontal polarization. Comparison of measurements with numerical predictions is presented. The results give idea about additional insertion loss imposed by window blinds for indoor signal reception.

Short-Term Terrain Diffraction Measurements: Preliminary Results

Autoři: Kvičera, M., Valtr, P., Ing. Tomáš Kořínek, Ph.D., prof. Ing. Pavel Pechač, Ph.D., Grabner, M., Kvičera, V., Martellucci, A.
Publikace: Proceedings of the 7th European Conference on Antennas and Propagation (EUCAP 2013). Piscataway: IEEE, 2013. pp. 52-55. ISBN 978-88-907018-3-2.
Rok: 2013

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper, we present first results of a shortterm measurement campaign aimed at terrain diffraction measurements. The campaign was held during August and September 2012 in the area of the Czech Republic and comprised using truck mounted access platforms to achieve a number of Tx and Rx station heights. Based on the experimental data obtained at frequencies ranging from L- to Q-band, a brief comparison between the measurements and selected propagation models is given as well.

Space Diversity Analysis for Low Elevation Links in a Wooded Area

Autoři: Šimůnek, M., prof. Ing. Pavel Pechač, Ph.D., Pérez-Fontán, F.
Publikace: Proceedings of the 7th European Conference on Antennas and Propagation (EUCAP 2013). Piscataway: IEEE, 2013. pp. 2281-2284. ISBN 978-88-907018-3-2.
Rok: 2013

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper we analyze the link between an UAV and a ground control station in a wooded area for study the possible use of space diversity methods. We reproduce the UAV link by performing experiment using a remotely controlled airship and a four channel receiver with two orthogonally polarized patch antennas. We present the possible values of diversity gain and its dependence on antennas mutual distance and elevation angle. Moreover we compare the results with data from an open field measurement.

Space Diversity Gain in Urban Area Low Elevation Links for Surveillance Applications

Autoři: Šimůnek, M., Fontan, F.P., prof. Ing. Pavel Pechač, Ph.D., Otero, F.J.D.
Publikace: IEEE Transactions on Antennas and Propagation. 2013, 61(12), 6255-6260. ISSN 0018-926X.
Rok: 2013

DOI: 10.1109/TAP.2013.2280874
Odkaz: https://doi.org/10.1109/TAP.2013.2280874
Pracoviště: Katedra elektromagnetického pole
Anotace:
In this communication we quantify the carrier-to-noise ratio, CNR, gains achieved using space diversity in a link reproducing the propagation conditions between a surveillance aerial vehicle, manned or unmanned, and a ground control station in an urban area at low elevation angles, in the 1–4 deg. range. The receiver is assumed to be at street level, i.e., it undergoes strong blockage effects. Such link differs from others, e.g., satellite or terrestrial, thus requiring an ad-hoc analysis including comprehensive measurements. Here, we describe a continuous wave, CW, measurement campaign where we used a four-channel receiver, i.e., we analyzed a 1x4 SIMO configuration. First, the correlation between branches was studied and then, we went on to verify the incremental CNR gains achieved by increasing the number of diversity branches. We also paid attention to the influence of the elevation angle within the limited elevation range considered. Moreover, for reference, we present a comparison with the theoretical diversity gains corresponding to four uncorrelated Rayleigh fading channels. In this study three usual combining strategies were also assessed: selection, SC, equal-gain, EGC, and maximal ratio, MRC.

The UAV Low Elevation Propagation Channel in Urban Areas: Statistical Analysis and Time-Series Generator

Autoři: Šimůnek, M., Fontán, F.P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2013, 61(7), 3850-3858. ISSN 0018-926X.
Rok: 2013

DOI: 10.1109/TAP.2013.2256098
Odkaz: https://doi.org/10.1109/TAP.2013.2256098
Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper we analyze the fading statistics of the link between a remotely controlled flying platform or an Unmanned Aerial Vehicle (UAV) and a ground receive station in an urban area. This link has a very specific geometry which is somewhere in between that of the purely terrestrial case (e.g., a macro-cell) and that of the land mobile satellite (LMS) systems. We have performed a model-based statistical analysis using unique experimental data, and following well-known models for LMS and terrestrial links with the conclusion that the Loo [1] (Rice+log-normal) model is the most suitable starting point for developing the wanted model; then several modifications have been introduced achieve a better match. Finally, we developed a narrowband time-series generator capable of reproducing the observed signal dynamics.

Broadband Spectrum Survey Measurements for Cognitive Radio Applications

Autoři: Urban, R., Ing. Tomáš Kořínek, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2012, 21(4), 1101-1109. ISSN 1210-2512.
Rok: 2012

Pracoviště: Katedra elektromagnetického pole
Anotace:
Building penetration loss models presented in our previous paper [1] were valid for various scenarios, propagation conditions, frequency bands, and hemispherical receiving antenna pointing towards zenith. These models had a significantly rising trend of penetration loss with increasing elevation angle of the link in common. In this paper we show that when working with such non-isotropic terminal antennas, this trend relates primarily to the elevation trend of the reference level [2] dependent on the receiving antenna radiation pattern. This is demonstrated by the results of single-input multiple-output (SIMO) measurement trials performed at L-band in an office building and a brick building in the city of Prague. Further, based on the detailed analysis, a method to modify the elevation trend of a particular penetration loss model for different receiving antenna radiation patterns is derived and experimentally validated.

Building Penetration Loss Modelling for Satellite Services At L-, S- and C-band

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 2427-2430. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6206508
Odkaz: https://doi.org/10.1109/EuCAP.2012.6206508
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents building penetration loss models at L-, S- and C-band that were derived from experimental data obtained during an extensive measurement campaign held in Prague during the years 2009 and 2010. After a brief introduction of the campaign and the data processing, the derived penetration loss models are presented in detail. These models are valid for common satellite-to-indoor scenarios in a typical urban area and unmodulated left-handed circularly polarized continuous wave signals. To validate the derived models, a comparison with selected relevant existing models is also provided.

Controlling Coverage Using New Concept of Pre-Installed Infrastructure

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 1161-1164. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6206278
Odkaz: https://doi.org/10.1109/EuCAP.2012.6206278
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper focuses on controlling coverage inside buildings via a new concept of Pre-Installed Infrastructure (PII) inside buildings based on the Distributed Antenna System (DAS). The new concept is based on the entire infrastructure, such as cables and antennas, being pre-installed during the construction of the building to form a large (Pre-) Distributed Antenna System. The system significantly decreases additional costs caused by any change in a building and controls coverage based on the user's position. Further, a new 3D semi-deterministic propagation model utilized for simulations of the PII influence is briefly described.

Controlling Propagation Environments Using Intelligent Walls

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 1-5. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6206517
Odkaz: https://doi.org/10.1109/EuCAP.2012.6206517
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper introduces the concept of an Active Wall (a wall equipped with an active frequency selective surface) as a powerful instrument to control the propagation environment. Further, the evolved Active Wall, referred to as an Intelligent Wall, is considered to be an autonomous part of a smart indoor environment for cognitive wireless networks. The Intelligent Wall is a wall inside a building equipped with an active frequency selective surface, simple low-cost sensors and a cognitive engine with machine-learning ability. Using simulations, it has been shown that a Smart environment based on Intelligent Walls can react to the immediate demands of an indoor wireless system, control radio coverage, and, consequently, influence overall system performance. The concept of Intelligent Walls is described and evaluated based on the simple implementation of an arrangement of two Intelligent Walls in a conference center scenario. All simulations of Smart environments are performed using a new 3D semi-deterministic propagation model which is described and briefly verified.

Estimation of Radio Refractivity Profile Gradient From Multiple LOS Links Using Artificial Neural Networks - First Results

Autoři: Jícha, O., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 1174-1177. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6206368
Odkaz: https://doi.org/10.1109/EuCAP.2012.6206368
Pracoviště: Katedra elektromagnetického pole
Anotace:
The question of a vertical refractivity gradient estimation is discussed herein. Artificial neural networks have been used as a tool to verify the existence of an unambiguous relationship between the vertical refractivity gradient and the electromagnetic wave strength measured at multiple heights by three antennas with direct visibility on the transmitter (line-of-sight links). Specific results of the estimation are presented and compared with meteorological measurements.

Excess Loss for High Elevation Angle Links Shadowed by a Single Tree: Measurements and Modeling

Autoři: Horák, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2012, 60(7), 3541-3545. ISSN 0018-926X.
Rok: 2012

DOI: 10.1109/TAP.2012.2196944
Odkaz: https://doi.org/10.1109/TAP.2012.2196944
Pracoviště: Katedra elektromagnetického pole
Anotace:
Results of experiments focusing on high-elevation links with a ground terminal shadowed by a single tree are introduced. The measurement trials were carried out at 2.0, 3.5, 5.0 and 6.5 GHz utilizing a remote-controlled airship as a pseudo-satellite for four different deciduous trees in summer and winter when trees are in full leaf and defoliated. The complete range of elevation angles typical of satellite/HAP services was addressed. Empirical models were proposed to account for excess loss as a function of its geometry. The applicability of terrestrial vegetation attenuation models on the given scenario is discussed.

First and Second Order Statistics of Clear-Air Attenuation on 11 GHz Terrestrial Path

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Jícha, O.
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 2401-2404. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6205913
Odkaz: https://doi.org/10.1109/EuCAP.2012.6205913
Pracoviště: Katedra elektromagnetického pole
Anotace:
Received power level fluctuations are measured on the terrestrial microwave link operating in 11 GHz band. Clear-air propagation effects such as tropospheric multipath and defocusing are observed to cause fading events with occasional attenuation peaks exceeding 20 dB for 0.01% of time on the 50 km long path. First and second order statistics of clear-air attenuation fluctuations are obtained from the three year period of measured data and compared with simple statistical models.

First Results of Rain Spatial Parameters Analyses for Optical Links

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 320-322. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6206163
Odkaz: https://doi.org/10.1109/EuCAP.2012.6206163
Pracoviště: Katedra elektromagnetického pole
Anotace:
Even though rain does not introduce the main negative influence affecting optical systems, it can cause high link outages. This paper represents an extension of a previous work related to rain spatial classification. It was found that the rain spatial parameter concept can also be extremely effectively applied to terrestrial and HAP systems, although specific adjustments have had to be made to the method. The method describing the spatial influence of rainfall on terrestrial radio microwave systems is now being tested with respect to optical links. The differences between both microwave and optical systems are discussed with regard to the new derived dependences.

Frequency Dependence of Vegetation Shadowing Loss for Satellite Services

Autoři: Horák, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 2445-2448. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6206548
Odkaz: https://doi.org/10.1109/EuCAP.2012.6206548
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents the results of a series of measurements to investigate the vegetation shadowing loss of high elevation links at L, S and C frequency bands. The results are analyzed and presented with respect to a frequency dependence of the vegetation shadowing loss and are based on experimental investigation performed during two different seasons, for three measurement scenarios and in a total of twelve different measurement locations.

Impulse Radio UWB Pulse Shaping for Cognitive Radio Applications

Autoři: Urban, R., Grace, D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Wireless Personal Communications. 2012, 63(3), 675-688. ISSN 0929-6212.
Rok: 2012

DOI: 10.1007/s11277-010-0158-6
Odkaz: https://doi.org/10.1007/s11277-010-0158-6
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper introduces a method of shaping impulse radio Ultra Wideband (UWB) pulses in the context of using higher than normal power transmissions and cognitive radio to provide the ability for such systems to avoid interference with primary users in shared radio spectrum. Using multiple shaping frequencies and a standard Gaussian pulse shape, pulses are shaped in the time domain, according to the requirements of the frequency spectrum in use, and any limits on power spectral density. Simulation results are presented for an example scenario based on measured data, along with a more general approach applicable to a free spectrum scenario. We show that the introduced shaping technique ensures that up to 98.8% of capacity of the UWB bandwidth within the conventional spectrum mask can be achieved for a time scaling factor of 11 ns and shaping frequency of 30 MHz. Capacity well in excess of the 100% achievable with the spectral mask is possible when the transmit power is permitted to increase in areas of 'white space' spectrum.

Influence of Antenna Characteristics on Elevation Dependence of Building Penetration Loss for High Elevation Links

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2012, 21(4), 1031-1035. ISSN 1210-2512.
Rok: 2012

Pracoviště: Katedra elektromagnetického pole
Anotace:
Building penetration loss models presented in our previous paper [1] were valid for various scenarios, propagation conditions, frequency bands, and hemispherical receiving antenna pointing towards zenith. These models had a significantly rising trend of penetration loss with increasing elevation angle of the link in common. In this paper we show that when working with such non-isotropic terminal antennas, this trend relates primarily to the elevation trend of the reference level [2] dependent on the receiving antenna radiation pattern. This is demonstrated by the results of single-input multiple-output (SIMO) measurement trials performed at L-band in an office building and a brick building in the city of Prague. Further, based on the detailed analysis, a method to modify the elevation trend of a particular penetration loss model for different receiving antenna radiation patterns is derived and experimentally validated.

Intelligent Walls as Autonomous Parts of Smart Indoor Environments

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IET Communications. 2012, 6(8), 1004-1010. ISSN 1751-8628.
Rok: 2012

DOI: 10.1049/iet-com.2010.0544
Odkaz: https://doi.org/10.1049/iet-com.2010.0544
Pracoviště: Katedra elektromagnetického pole
Anotace:
This study introduces the concept of an intelligent wall as an autonomous part of a smart indoor environment for cognitive wireless networks. Here, an intelligent wall is a wall inside a building equipped with an active frequency-selective surface, simple low-cost sensors and a cognitive engine with machine-learning ability. Using simulations, it has been shown that the smart environment based on intelligent walls can react to the immediate demands of an indoor wireless system, control radio coverage and, consequently, influence the overall system performance. The concept of the intelligent walls is described and evaluated based on a simple implementation of an arrangement of two intelligent walls in a conference centre scenario. Artificial neural networks were employed in the cognitive engine. Elementary orthogonal frequency division multiple access static system simulations are used to analyse the influence of the smart environment on the system performance. Results are discussed in detail and typical characteristics of the aforementioned system are derived and summarised.

Long-term Measurements of Refractive Index Structure Constant in Atmospheric Boundary Layer

Autoři: Jícha, O., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Stanislav Zvánovec, Ph.D., Grábner, M., Kvičera, V.
Publikace: Proceedings of SPIE - Optics in Atmospheric Propagation and Adaptive Systems XV. Washington: SPIE, 2012. pp. 1-8. ISBN 978-0-8194-9275-3.
Rok: 2012

Pracoviště: Katedra elektromagnetického pole
Anotace:
Results of long-term measurements of the refractive index structure constant in the boundary layer are introduced. The measurements were made on a 150-meter-high lattice mast equipped by nineteen meteorological sensors and one pressure sensor at the bottom of the mast. The Kolmogorov statistical theory of turbulence was used to calculate the refractive index structure constant C2n , allowing us to present annual cumulative distribution functions (CDFs) and seasonal quantiles. The quantiles of measured height dependence of the refractive index structure constant are also shown and compared with existing models (Hufnagel/Andrews/Phillips, SLC Day and Gurvich). Parameters of a linear model were calculated to fit the measured median height profile of the refractive index structure constant with the uncertainty of measurements also being addressed.

On the Short-term Time Evolution of Elevated Ducting Layers

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Jícha, O.
Publikace: Proc. of 2012 Loughborough Antennas & Propagation Conference. Loughborough: Loughborough University, 2012. pp. 1-4. ISBN 978-1-4673-2219-5.
Rok: 2012

DOI: 10.1109/LAPC.2012.6402992
Odkaz: https://doi.org/10.1109/LAPC.2012.6402992
Pracoviště: Katedra elektromagnetického pole
Anotace:
Vertical profiles of atmospheric refractivity are obtained from the tower measurement of temperature and humidity profiles with a vertical resolution less than eight meters and a e resolution one minute. Profiles are described using a modified Webster model with model parameters fitted by nonlinear regression. The time series of fitted parameters show the short-term time evolution of elevated ducting layers. Several typical examples of evolving ducting layers are provided and discussed.

Parameters of Vertical Profiles of Temperature, Humidity and Refractive Index of Air in the Lowes Troposphere

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Jícha, O.
Publikace: Proceedings of the 9th International Symposium on Tropospheric Profiling. Noordwijk: ESA Publications Division, 2012. pp. 1-4. ISBN 978-90-815839-4-7.
Rok: 2012

Pracoviště: Katedra elektromagnetického pole
Anotace:
Vertical profiles of temperature and relative humidity of air are measured on the 150 meter tall mast at 19 heights with average separation less than 8 meters and with sampling rate 1 minute. Vertical profiles of atmospheric refractivity are obtained and occurrence of ducting layers is analysed using nonlinear regression. Ground based and elevated ducting layers are observed. Temporal evolution of ducting layers is described by means of typical examples. Long term empirical statistics of layer parameters are provided and interrelations between different parameters of vertical profiles are pointed out.

Propagation Measurements in a Wide Range of Elevation Angles Using a Remote-Controlled Airship

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 2012 International Symposium on Antennas and Propagation. Tokyo: The Institute of Electronics, Information and Communication Engineers, 2012. pp. 632-635. ISBN 978-4-88552-269-7.
Rok: 2012

Pracoviště: Katedra elektromagnetického pole
Anotace:
During the period from 2008 to 2012, we successfully carried out three different types of propagation measurements with a remote-controlled airship [1]-[6]. These campaigns covered satellite-to-indoor channel and attenuation by vegetation measurements for high elevation angles as well as UAV channel measurements for low elevation angles. Different types of measurement systems were utilized to address single-input single-output (SISO), single-input multiple-output (SIMO), multiple-input single-output (MISO) and combined SIMO/MISO propagation channels for frequencies ranging from L- to C-band. The aim of this paper is to present in detail the measurement methods applied during the corresponding propagation measurements and to provide general guidelines and understanding that can be useful when such measurements are carried out.

Space Diversity Analysis for Low Elevation Links in Urban Areas

Autoři: Šimůnek, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 6th European Conference on Antennas and Propagation (EUCAP 2012). Piscataway: IEEE, 2012. pp. 1165-1168. ISBN 978-1-4577-0918-0.
Rok: 2012

DOI: 10.1109/EuCAP.2012.6206323
Odkaz: https://doi.org/10.1109/EuCAP.2012.6206323
Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper we analyze the possible use of diversity methods for a link between an UAV and a ground control station in an urban area. We describe a measurement campaign which reproduces the UAV link using a four channel receiver. The whole system can be classified as SIMO 1x4. We briefly introduce diversity methods which can be used to improve the link performance. Finally we present the results of a comparison of all the methods, and an analysis of elevation angles, the influence of location on diversity gain, a distribution analysis and an analysis of the number of channels are performed. The conditions for diversity techniques are favorable and all three methods enhance link performance. The diversity gain is not significantly dependent on the elevation angle or on the location of the receiver.

Advanced 3D Indoor Propagation Model: Calibration and Implementation

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EURASIP Journal on Wireless Communications and Networking. 2011, 2011(180), 1-10. ISSN 1687-1499.
Rok: 2011

DOI: 10.1186/1687-1499-2011-180
Odkaz: https://doi.org/10.1186/1687-1499-2011-180
Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper deals with a software tool implementing a semi-deterministic model which provides swift predictions, accounts for all significant physical phenomena while utilizing a clear-cut description of material properties. The software can predict signal coverage, delay profiles and angle of arrivals for receivers located anywhere in a scenario. Measured narrowband, as well as wideband, data are presented and the basic principles of the computer optimisation utilized in the tool are shown. Optimised results are compared with the measured ones and deviation is determined.

Attenuation Due to Vegetation for Satellite Services: Winter Season Measurement

Autoři: Horák, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 5th European Conference on Antennas and Propagation (EuCAP). Piscataway: IEEE, 2011. pp. 1938-1940. ISBN 978-88-8202-074-3.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper we report the results of a series of measurements to investigate the influence of vegetation on satellite communications in the L, S and C bands during the winter months. These measurements were performed by a 9m-long remote-controlled airship used as a pseudo-satellite to carry a narrowband transmitter while the receiver station was located on the ground at four different locations inside small groves in order to involve different types of vegetation. Flyovers were performed to obtain data for the widest range of elevation and azimuth angles. The measurements presented, performed during March 2010, are an extension to the results of the measurement campaign carried out in Stromovka Park in the city of Prague during June 2009. A short comparison with data acquired during the summer is also presented.

Building Penetration Loss for Satellite Services at L-,S- and C band: Measurement and Modeling

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2011, 59(8), 3013-3021. ISSN 0018-926X.
Rok: 2011

DOI: 10.1109/TAP.2011.2158963
Odkaz: https://doi.org/10.1109/TAP.2011.2158963
Pracoviště: Katedra elektromagnetického pole
Anotace:
An extensive measurement campaign, covering a representative set of typical buildings in an urban area and aimed at building penetration loss for satellite services at L-, S- and C-band, was performed in Prague in the summer of 2009. Throughout the measurements, a remote-controlled airship was used as a pseudosatellite carrying a transmitter which provided unmodulated continuous wave left-handed circularly polarized signals at 2.0 GHz, 3.5 GHz, 5.0 GHz, and 6.5 GHz. A description of the measurement campaign is provided here, together with a thorough analysis of the resulting experimental data. A significant dependence on elevation angle is reported for line-of-sight and non-line-of-sight propagation conditions separately. Subsequent steps to introduce elevation dependent empirical models at corresponding frequencies follow. Finally, a comparison to other studies dealing with building penetration loss for high elevation angles is presented.

Elevation Dependence of Building Penetration Loss for Satellite Services at 3.5 GHz and 5.0 GHz

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: European Microwave Week 2011 "Wave to the Future" - Conference Proceedings. London: Horizon House Publications, 2011. pp. 682-685. ISBN 978-2-87487-021-7.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
Based on experimental results obtained during an extensive measurement campaign aimed at building penetration loss for satellite services, an elevation dependence of penetration loss is discussed in this paper. For the analysis, three different types of typical buildings in an urban area were selected. These case-study buildings are compared here by addressing the trend and absolute values of the corresponding elevation-dependent penetration loss with respect to the particular measurement scenario as well as their respective structures and building material.

Estimation of the Refractivity Structure of the Lower Troposphere From Measurements on a Terrestrial Multiple-Receiver Radio Link

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: IEEE Transactions on Antennas and Propagation. 2011, 59(5), 1707-1715. ISSN 0018-926X.
Rok: 2011

DOI: 10.1109/TAP.2011.2122234
Odkaz: https://doi.org/10.1109/TAP.2011.2122234
Pracoviště: Katedra elektromagnetického pole
Anotace:
A matched field technique is used for remote sensing of refractivity profile. The method relies on electromagnetic propagation simulation to estimate the height profile of radio refractivity in the lower atmosphere by comparing theoretical predictions with measurements on a terrestrial radio link. The objective is to discover whether small variations of the air's refractive index can be detected in the lowest part of atmosphere, up to 150 m above the ground. The resultant estimations of the height profile of refractivity are compared with the measured refractivity profile obtained from meteorological sensors at different heights. The results show a close agreement between the estimated and measured refractivity profiles during periods of deep fading events.

Excess Loss Model for Low Elevation Links in Urban Areas for UAVs

Autoři: Šimůnek, M., prof. Ing. Pavel Pechač, Ph.D., Fontan, P.
Publikace: Radioengineering. 2011, 20(3), 561-568. ISSN 1210-2512.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper we analyze the link between an UAV and a ground control station in an urban area. This link shows a unique geometry which is somewhere in between the purely terrestrial (e.g., a macro-cell channel) and the land mobile satellite case (LMS). We describe a measurement campaign which reproduces the UAV link conditions and shows how the excess loss is mainly dependent on the elevation angle and fairly independent of the distance. Finally, we propose a simple physical model for predicting the excess loss based on a combination of diffracted and reflected components. Results from this model are in good agreement with the measurements.

Influence of Modelling Diffraction on Electromagnetic Wave Propagation Predictions in Subterranean Galleries

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 5th European Conference on Antennas and Propagation (EuCAP). Piscataway: IEEE, 2011. pp. 1751-1754. ISBN 978-88-8202-074-3.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper focuses on modeling diffraction phenomenon and its influence on electromagnetic wave predictions in subterranean galleries. A new approach to modeling diffraction is briefly mentioned along with basic parameters used for modeling. In order to show the influence of diffraction phenomena on simulation results, two typical subterranean galleries (a single bending corridor and a more complex system of corridors) are simulated under different conditions - with and without considering diffraction in each. Significant differences are described and commented upon. Results are processed on a statistical basis and recommendations based on the results are made.

Influence of Receiver Position on Building Penetration Loss at 5.0 GHz for High Elevation Angles

Autoři: Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 5th European Conference on Antennas and Propagation (EuCAP). Piscataway: IEEE, 2011. pp. 3559-3561. ISBN 978-88-8202-074-3.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
Based on experimental data obtained during an extensive measurement campaign aimed at building penetration loss for satellite services, this paper presents the influence of the receiver position inside three case-study buildings. After a brief description of the measurement system, the corresponding measurement scenarios are described in detail. Finally, results at the frequency of 5.0 GHz are discussed for four different measurement sites.

Initial Results of Foliage Attenuation Measurements of a Tree-lined Passage at L, S and C Bands for High Elevation Angle Links

Autoři: Horák, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: ISAP 2011 - Proceedings. Seoul: Korea Institute of Electromagnetic Engineering and Society (KIEES), 2011. pp. 1-4. ISBN 978-89-5708-211-9.
Rok: 2011

DOI: 10.1109/URSIGASS.2011.6050869
Odkaz: https://doi.org/10.1109/URSIGASS.2011.6050869
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents the initial results of a series of measurements to investigate the vegetation attenuation for a terminal of a high elevation link inside a tree alley passage at 2.0, 3.5, 5.0 and 6.5 GHz. The measurements were performed over the course of two seasons at two positions using a 9-meter-long remote-controlled airship as a pseudo-satellite.

Intelligent Controlling of Wireless Cognitive Networks in Indoor Scenarios Using Intelligent Walls

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Workshop 2011. Praha: České vysoké učení technické v Praze, 2011. pp. 1-3.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
The project is focused on the new approach to controlling cognitive networks. The main idea lies in implementation of a new concept of so called intelligent wall, i.e. walls placed inside a building which are able to adjust their electrical properties on the basis of current needs of the network users. The project deals with the modeling of such walls and their effect on the wireless system performance. The aim of this project is to design a system including intelligent walls which will be able to control itself autonomously. Such a system will be able to be included to existing cognitive systems. Cognitive systems are wireless networks which are able to change parameters of communication channel dynamically in order to achieve the maximal throughput of the system.

Measured and Simulated Fluctuations of Received Power on 11 GHz Terrestrial Path Using Vertical Profiles of Atmospheric Refractivity

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Jícha, O.
Publikace: Proceedings of the 5th European Conference on Antennas and Propagation (EuCAP). Piscataway: IEEE, 2011. pp. 190-193. ISBN 978-88-8202-074-3.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
The measurement of received power fluctuations on the terrestrial 11 GHz, 50 km path together with the measurement of the vertical profiles of atmospheric refractivity at the receiver site are presented. The parabolic equation method is utilized to test the validity of different assumptions about the horizontal distribution of refractivity above an irregular terrain. Measured and simulated time series of received signal are compared in terms of their cumulative distribution functions. The better agreement between simulation and measurement is achieved for horizontally independent refractivity profiles where the refractivity is assumed to be constant with the height above a sea level.

On the Uncertainty of Refractivity Height Profile Measurements

Autoři: Jícha, O., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: IEEE Antennas and Wireless Propagation Letters. 2011, 10 983-986. ISSN 1536-1225.
Rok: 2011

DOI: 10.1109/LAWP.2011.2168370
Odkaz: https://doi.org/10.1109/LAWP.2011.2168370
Pracoviště: Katedra elektromagnetického pole
Anotace:
The standard uncertainty of indirect refractivitymeasurements gained from measurements of pressure, temperature, and humidity is discussed herein. The resulting uncertainty is derived theoretically, based on propagating uncertainties of meteorological sensors through a refractivity calculation, with an example of its impact on actual measurements of a vertical refractivity profile and its gradient also submitted.

Seasonal Additional Attenuation in Woodlands for Satellite Services at L-, S- and C-Bands

Autoři: Horák, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2011, 59(12), 4865-4867. ISSN 0018-926X.
Rok: 2011

DOI: 10.1109/TAP.2011.2165507
Odkaz: https://doi.org/10.1109/TAP.2011.2165507
Pracoviště: Katedra elektromagnetického pole
Anotace:
Results of measurement trials at 2.0, 3.5, 5.0 and 6.5 GHz focused on high elevation links with a ground terminal inside a forested area are presented. Previous measurements during summer vegetation shadowing in full leaf were significantly expanded upon in new locations and, in addition, by conducting trials during winter. New empirical linear models were derived for both summer and winter at a broad frequency range taking into consideration elevation angles between 25 to 90 degrees. The models can be used to estimate average, minimum and maximum values of the additional vegetation attenuation in moderate climate woodlands.

Troposphere Refraction State Classification Using Measured Attenuation of Non-Line-of-Sight Microwave Links

Autoři: Jícha, O., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: Proceedings of the 5th European Conference on Antennas and Propagation (EuCAP). Piscataway: IEEE, 2011. pp. 1723-1726. ISBN 978-88-8202-074-3.
Rok: 2011

Pracoviště: Katedra elektromagnetického pole
Anotace:
A new method is introduced to determine the troposphere refraction state from the measured field strength of a non-line-of-sight microwave link. The classification procedure is proposed for diffraction paths with a single knife-edge obstacle and recognizes three states of radiowave propagation in the atmosphere: sub-refraction, super-refraction and standard atmosphere. Comparisons of the classification results based on the measured field strength and meteorological measurements are presented to validate the method.

Validation of Rain Spatial Classification for High Altitude Platform Systems

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2011, 59(7), 2746-2750. ISSN 0018-926X.
Rok: 2011

DOI: 10.1109/TAP.2011.2152325
Odkaz: https://doi.org/10.1109/TAP.2011.2152325
Pracoviště: Katedra elektromagnetického pole
Anotace:
Previous work on rain spatial classification for terrestrial PMP radio systems has been extended in this communication to stratospheric systems-high altitude platform systems. It was found that the rain spatial parameter concept can also be effectively applied to HAP systems, although specific adjustments have had to be made to the method. The differences between terrestrial and stratospheric systems are discussed with regard to the new derived dependences.

Vertical Dependence of Refractive Index Structure Constant in Lowest Troposphere

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Jícha, O.
Publikace: IEEE Antennas and Wireless Propagation Letters. 2011, 10 1473-1475. ISSN 1536-1225.
Rok: 2011

DOI: 10.1109/LAWP.2011.2178809
Odkaz: https://doi.org/10.1109/LAWP.2011.2178809
Pracoviště: Katedra elektromagnetického pole
Anotace:
Vertical profiles of atmospheric refractivity are indirectly measured at heights of up to 150 m above ground using meteorological sensors located at 19 heights. The structure constant of the refractive index C n is calculated from data measured over a one-year period using its definition relation. Linear regression in heights is applied to a structure constant vertical dependence to obtain single and joint annual statistics of the near ground value of C n and of its vertical gradient in the lowest troposphere. Approximate probability models are given with C n being lognormal and the vertical gradient normally distributed.

A Terrestrial Multiple-Receiver Radio Link Experiment at 10.7 GHz: Comparisons of Results with Parabolic Equation Calculations

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: Radioengineering. 2010, 19(1), 117-121. ISSN 1210-2512.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
This work presents the results of a terrestrial multiple-receiver radio link experiment at 10.7 GHz. Results are shown in the form of the power levels recorded at several antennas attached to a receiving mast. Comparisons of the measurement data with theoretical predictions using a parabolic equation technique show that, due to the complex propagation environment of the troposphere in terms of the refractive index of air, closer agreement between measurements and simulations can be achieved during periods of standard refractive conditions.

An Evaluation of Approaches for Modeling of Terrestrial, HAP and Satellite Systems Performance during Rain Events

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of PIERS 2010 in Cambridge. Cambridge, MA: The Electromagnetics Academy, 2010. pp. 1078-1080. ISSN 1559-9450. ISBN 978-1-934142-14-1.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents the results from site-specific simulations of route diversity performance in case of High Altitude Platform system, terrestrial system and satellite system during specific rain events. Based on the radar rainfall database, route diversity dependences on altitude of transmitter were studied using the simulation tool. The main goal of the paper is to adopt concept for HAP systems from investigations of both terrestrial point-to-multipoint systems and satellite systems operating in millimeter frequency bands.

Analyses of Some Realtions among Received Signal Levels, Effective Earth-radius Factors and Weather States

Autoři: Kvičera, V., Grábner, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: European Microwave Week 2010 "Connecting the World" Conference Proceedings. London: Horizon House Publications, 2010. pp. 1329-1332. ISBN 978-2-87487-019-4.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
An experimental multiple-receiver radio link working at 10 GHz on 50 km path is described. Received signal levels and meteorological data are gathered. Analyses of some relations among received signal levels, effective Earth-radius factors and current weather states are given. The influence of meteorological conditions on the received signal is discussed.

Atmospheric Refractivity Evaluation Improved Using Artificial Neural Networks

Autoři: Ing. Martin Mudroch, Ph.D., prof. Ing. Pavel Pechač, Ph.D., Grábner, M., Kvičera, V.
Publikace: Proceedings of the 4th European Conference on Antennas and Propagation. Piscataway: IEEE, 2010. pp. 1-4. ISBN 978-84-7653-472-4.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper describes a new progress in evaluating measured data from a unique, experimental, multiple-receiver terrestrial radio link used for remote sensing. The refractivity index height profile of the lowest troposphere layers is evaluated and the classification process is discussed. We are comparing different sizes and architectures of feed-forward artificial neural networks and their learning parameters.

Building Penetration Loss Measurements for Satellite-to-Indoor Systems: Preliminary Results

Autoři: Kvičera, M., Horák, P., Ing. Tomáš Kořínek, Ph.D., Zela, J., Šimůnek, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 4th European Conference on Antennas and Propagation. Piscataway: IEEE, 2010. pp. 1-4. ISBN 978-84-7653-472-4.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents preliminary results obtained from an extensive measurement campaign aimed at building penetration loss. We have concentrated on three different factors affecting this loss - the elevation, the frequency and the floor number of the investigated building. Results for two different measurement sites at 2.0 GHz and 5.0 GHz inside an old brick three-storey office building located in Prague are provided together with a brief description of the measurement system used during the measurement campaign.

Controlling the Short-Range Propagation Environment Using Active Frequency Selective Surfaces

Autoři: Šubrt, L., Grace, D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2010, 19(4), 610-617. ISSN 1210-2512.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with a new approach to the control of the propagation environment in indoor scenarios using intelligent walls. The intelligent wall is a conventional wall situated inside a building, but equipped with an active frequency selective surface and sensors. The intelligent wall can be designed as a self-configuring and self-optimizing autonomous part of a collaborative infrastructure working within a high-capacity mobile radio system. The paper shows how such surfaces can be used to adjust the electromagnetic characteristics of the wall in response to changes in traffic demand, monitored using a network of sensors, thereby controlling the propagation environment inside the building. The positive influence of intelligent walls on system performance is shown and results obtained from the simulations are shown and discussed.

Effect of Antenna Power Roll-Off on the Performance of 3G Cellular Systems from High Altitude Platforms

Autoři: Holiš, J., Grace, D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Aerospace and Electronic Systems. 2010, 46(3), 1468-1477. ISSN 0018-9251.
Rok: 2010

DOI: 10.1109/TAES.2010.5545201
Odkaz: https://doi.org/10.1109/TAES.2010.5545201
Pracoviště: Katedra elektromagnetického pole
Anotace:
An investigation into the impact of antenna radiation patterns on the performance of a 3G mobile communication system provided a single high-altitude platform (HAP) is presented. Use of elliptical and circular beam antennas is examined for a 91-cell system. Crucial performance parameters are shown to be the mainlobe power roll-off and sidelobe level. Elliptical beam antennas are proven to provide the best solution, but circular beam antennas with their gain adjusted to reduce the degree of cell overlap and compensate for increasing path loss are shown to provide similar performance, with the advantage that they are practically more realizable. It is shown that poorer overlap performance can be partially compensated for by an increased power roll-off at the cell edge, a strategy that is employed in the case of the gain adjusted circular beam antennas.

Effective Earth Radius Variation and Diffraction Fading on Terrestrial Path

Autoři: Grábner, M., Kvičera, Václav, prof. Ing. Pavel Pechač, Ph.D., Jícha, O.
Publikace: 2010 Loughborough Antennas and Propagation Conference (LAPC). Loughborough: Loughborough University, 2010. pp. 105-108. ISBN 978-1-4244-7304-5.
Rok: 2010

DOI: 10.1109/LAPC.2010.5666792
Odkaz: https://doi.org/10.1109/LAPC.2010.5666792
Pracoviště: Katedra elektromagnetického pole
Anotace:
Effective earth radius factor (k factor) is an important parameter for the assessment of clear-air propagation on terrestrial paths. Its variation obtained from the measurement of vertical distribution of atmospheric refractivity is studied in the paper. Two year statistics of the k factor are given for the whole year and different months. The related clear-air propagation impairment on the 10 GHz terrestrial path is shown in the example. A typical diffraction fading event is analyzed by a comparison of measured time evolution of received signal level and of a simulated one using measured refractivity. A direct correspondence between the time evolution of the effective earth radius factor and of attenuation due to reduced path clearance is so demonstrated.

Frequency Dependence of Attenuation Due to Vegetation for Satellite Services

Autoři: Horák, P., Kvičera, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Antennas and Wireless Propagation Letters. 2010, 9 142-144. ISSN 1536-1225.
Rok: 2010

DOI: 10.1109/LAWP.2010.2045150
Odkaz: https://doi.org/10.1109/LAWP.2010.2045150
Pracoviště: Katedra elektromagnetického pole
Anotace:
This letter presents the results of vegetation loss measurements at 2.0, 3.5, 5.0, and 6.5 GHz for elevation angles ranging from 20 to 90 degrees. The excess attenuation due to vegetation was measured at four different wooded locations using a remote-controlled airship as a pseudo-satellite. Measurements taken in an open field were used as a reference. The results are given as additional attenuation averaged over the whole range of azimuth and elevation angles for circular polarization. Average results from all four locations vary from 9 dB at 2.0 GHz to 14.5 dB at 6.5 GHz. Linear frequency dependence of vegetation attenuation was observed, and a corresponding empirical model providing the additional vegetation loss as a function of the frequency was derived in closed form. The results are then compared to the literature.

Integration of Ultra Wideband Signals in the Time Domain to Education

Autoři: Urban, R., prof. Ing. Pavel Pechač, Ph.D., Šubrt, L.
Publikace: Workshop 2010. Praha: České vysoké učení technické v Praze, 2010. pp. 148-149. CTU Reports. ISBN 978-80-01-04513-8.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
The goal of this project is to enrich the education (not only practice, also lectures) by the new procedures using time domain propagation of the ultra wideband (UWB) pulses. It is a modern approach for physical layer of communication technologies (IEEE 802.15.4a). Within the framework of this project will be the modern time domain approach included into the education. It will be created new measurement workplace for bachelor and engineer education program. This workplace will be used for projects and thesis too. The several scenarios will be examined for differences of propagation between the frequency domain and the time domain. In the international conferences and journal papers it is written, that the time domain measurement is able to be used instead of the time consuming frequency domain measurement.

Multipath Fading Measurement and Prediction on 10 GHz Fixed Terrestrial Link

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Ing. Martin Mudroch, Ph.D.,
Publikace: Proceedings of 15th Conference on Microwave Techniques COMITE 2010. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2010. pp. 145-148. ISBN 978-1-4244-6351-0.
Rok: 2010

DOI: 10.1109/COMITE.2010.5481330
Odkaz: https://doi.org/10.1109/COMITE.2010.5481330
Pracoviště: Katedra elektromagnetického pole
Anotace:
Multipath propagation events are observed on the 50 km long fixed terrestrial link operating in 10 GHz band. Several receivers are located in different heights. Two year statistics of attenuation and enhancement due to multipath are obtained from measured signal fluctuations in different heights. The results are compared with cumulative distributions predicted by the two methods - the ITU-R method and the VUS method which is currently used for the planning of radio-relay links in the Czech Republic. The predicted distributions of attenuation provide slightly higher exceedance probabilities than measured.

New Approach to Modeling of Diffuse Reflection and Scattering for Millimeter-wave Systems in Indoor Scenarios

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Stanislav Zvánovec, Ph.D.,
Publikace: Proceedings of PIERS 2010 in Cambridge. Cambridge, MA: The Electromagnetics Academy, 2010. p. 1068-1071. ISSN 1559-9450. ISBN 978-1-934142-14-1.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
A new approach to modeling diffuse reflection and scattering for millimeter-wave band based on a fast and simple semi-deterministic principle is presented. The model is based on the combination of pre-computed radiation patterns and a fast semi-deterministic algorithm. The principle and function of this model are explained as well as tested in a common indoor are compared with results received from a classical ray-based model and significant differences are discussed in detail.

On a Definition of Building Penetration Loss for High Elevation Angles

Autoři: Kvičera, M., Horák, P., prof. Ing. Pavel Pechač, Ph.D., Perez-Fontan, F.
Publikace: IEEE Transactions on Antennas and Propagation. 2010, 58(12), 4115-4118. ISSN 0018-926X.
Rok: 2010

DOI: 10.1109/TAP.2010.2078470
Odkaz: https://doi.org/10.1109/TAP.2010.2078470
Pracoviště: Katedra elektromagnetického pole
Anotace:
Different methods of defining building penetration loss for high elevation angle paths exist. A key factor is the selection of the reference level. A comparison of four of the most common types of reference levels used to determine building penetration loss for high elevation angles is presented based on a measurement trial using unmodulated carriers at 2.0 GHz and 5.0 GHz performed at a three-storey office building. It was shown that the choice of reference level significantly affects the results obtained. Particular cases are discussed and general recommendations on the selection of the reference level for building penetration loss measurement are provided.

Pulse Shaping for Impulse Radio UWB

Autoři: Urban, R., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: ISAP 2010 (International Symposium on Antennas and Propagation). Macao: Universidade de Macau, 2010. pp. 65-68.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
An increasing shortage of free frequency bands is creating opportunities for the usage of intelligent cognitive systems as this type of radio system can change its system parameters, e.g. radiation power and frequency but it is necessary to find an optimal physical layer for this technology. This paper describes a system which demonstrates the possibility of using an Ultra Wideband (UWB) system as an interference avoidance system as used in cognitive systems. Currently, UWB technology is used by the classical OFDM approach that features classical narrowband principles in a wideband channel. We propose using pulses, instead of typical harmonic carriers, for carrying information. A typical wideband mixer is used for UWB pulse shaping.

Semi-Deterministic Propagation Model for Subterranean Galleries and Tunnels

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2010, 58(11), 3701-3706. ISSN 0018-926X.
Rok: 2010

DOI: 10.1109/TAP.2010.2072898
Odkaz: https://doi.org/10.1109/TAP.2010.2072898
Pracoviště: Katedra elektromagnetického pole
Anotace:
A three-dimensional, semi-deterministic model for wave propagation in subterranean galleries and tunnels is introduced. The model uses a combination of deterministic ray-launching techniques and a stochastic approach to provide efficient predictions that avoid complex calculations of electromagnetic phenomena while preserving the ability to consider reflection, absorption and penetration, as well as diffuse scattering. There is no need to provide a precise definition of the walls in terms of their material electrical parameters and roughness. The wall properties are efficiently described using just three probabilistic parameters that can be calibrated by measurements. Experimental data for three various subterranean scenarios were used to validate the model's functionality. The scenarios were chosen with regard to validating the model function for different frequencies, cross-sections, lengths and shapes.

The Influence of Dynamic Changes of Indoor Scenarios on Electromagnetic Wave Propagation

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 4th European Conference on Antennas and Propagation. Piscataway: IEEE, 2010. pp. 1-5. ISBN 978-84-7653-472-4.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
The effect of common dynamic changes such as opening and closing doors or windows, as well as minor floor alternations in buildings on an electromagnetic wave propagation environment is studied in this paper. A sample scenario is used in order to show how these situations over the course of an ordinary work day influence wave propagation. Both signal coverage and impulse response are predicted in order to obtain more complete information about the environment. A 3D semi-deterministic model considering all significant physical phenomena influencing wave propagation is used. Simulation results are noted and their actual influence on wireless system performance is evaluated.

Ultra Wideband Pulse Shaping Using Freauency Mixer

Autoři: Urban, R., Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE International Microwave Workshop Series on RF Front-ends for Software Defined and Cognitive Radio Solutions - Book of Abstracts. Aveiro: University of Aveiro, 2010. pp. 1-4. ISBN 978-1-4244-5752-6.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
The entire alck of free frequency bands gives opportuinity to intelligent cognitive systems. THis type of radio system is able to change its system parameters, e.g. radiation power and frequency. The presented system describes possibility how to shape an Ultra Wideband (UWB) pulse using a typical frequency mixer. The measurement results are included in this paper.

Vegetation Attenuation by a Single Tree for High Elevation Angles at 2.0 and 6.5 GHz

Autoři: Horák, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: ISAP 2010 (International Symposium on Antennas and Propagation). Macao: Universidade de Macau, 2010. pp. 69-72.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
With the new requirements imposed on wireless satellite services, such as a wide range of services, mobility, availability, etc., the need has arisen to investigate the propagation channel for high elevation angles under vegetation blockage conditions. The appearance of a forested medium in the path of a satellite, terrestrial or any microwave communication link has a significant effect on the quality of the received signal. The aim of this paper is to present the results from the measurement trails focused on investigation the vegetation attenuation by a single tree. A remote-controlled airship was utilized as a pseudo-satellite to carry the payload during the measurement trials while empirical data were obtained in both the summer and winter seasons for wide range of elevation angles at two different frequencies.

Vegetation Attenuation Measurements at 2 GHz using a Remote-Controlled Airship - Initial Results

Autoři: Horák, P., Kvičera, M., Šimůnek, M., Ing. Tomáš Kořínek, Ph.D., Zela, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 4th European Conference on Antennas and Propagation. Piscataway: IEEE, 2010. pp. 1-4. ISBN 978-84-7653-472-4.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to describe tree attenuation measurements at 2 GHz in four different locations inside vegetation, and at three different positions for a single tree shadowing. The purpose of this measurement campaign was to use a 9-meter long remote-controlled airship as a pseudosatellite. The transmitting station was located on the airship as a payload and receiving station inside or nearby the vegetation. Subsequently, the received signal strength was measured at each position as a function of elevation angles ranging from 25 to 90 degrees. Measurements taken in an open field were used as a reference. The measured data are still being processed, however, the initial results are shown. The results for locations inside the vegetation and the single tree are compared as well.

Workplace for Measurement of UWB signals

Autoři: Urban, R., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Workshop 2010. Praha: České vysoké učení technické v Praze, 2010. pp. 128-129. CTU Reports. ISBN 978-80-01-04513-8.
Rok: 2010

Pracoviště: Katedra elektromagnetického pole
Anotace:
Today, access to radio spectrum is difficult as it is restricted by a radio regulatory of every country. Large parts of the radio spectrum are allocated to licensed radio services. Open access to some part of the radio spectrum is permitted with very low transmission power, for example Ultra WideBand system works in huge frequency bandwidth and with very low power spectral density. The pulse shaping technique with the cognitive radio ideas could be solution to increase range of the UWB system by increasing power in non-occupied frequency bands that is one of the most uncomfortable limitations of the ultra wideband low power systems.

A 3D Model for Wideband Propagation Predictions in Tunnels

Autoři: Šubrt, L., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 2165-2168. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with indoor electromagnetic wave propagation modelling. The deterministic models implementing a novel approach, namely the Motif Model and the new 3D model, which are able to compute both narrowband and wideband results, are proposed and the basic principles underlying their function are explained. Simulated results obtained from these models are provided and verified.

A Study on the Possibilities of Providing Signal Coverage for Wireless Systems from High Altitude Platforms

Autoři: Horák, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 1333-1336. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper provides a study on possibilities of signal coverage for wireless systems provided from High Altitude Platforms (HAPs). Coverage by a single antenna forming a cell on the ground beneath the patform is considered. The presented study helps to understand that the coverage is not given just by geometry, i.e. the optical visibility to the patform is not sufficient. The key limiting factor is also the power budget requirements and the antenna. The platform altitude from 0 to 100 km is analyzed.

Beam Propagation Simulations of Quasioptical Systems

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Kvičera, M., Kuchařík, P., Černý, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 3702-3704. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
A quasioptical approach using Gaussian beams can be applied to enumerate propagation aspects at millimetre and submillimetre wave bands. The paper introduces results obtained by a measurement campaign focused on Gaussian beam aspects. Based on measured statistics, simulations by using a quasioptical approach were introduced. Results from simulatin of system within indoor environment were compared to those obtained by classical ray-tracing method and specific features of both approaches were revealed.

Classification and Prediction of Lower Troposphere Layers Influence on RF Propagation Using Artificial Neural Networks

Autoři: Ing. Martin Mudroch, Ph.D., prof. Ing. Pavel Pechač, Ph.D., Grábner, M., Kvíčera, V.
Publikace: Advances in Neuro-Information Processing. Berlin: Springer, 2009. p. 893-900. Lecture Notes in Computer Science. vol. 5506. ISSN 0302-9743. ISBN 978-3-642-02489-4.
Rok: 2009

DOI: 10.1007/978-3-642-02490-0_109
Odkaz: https://doi.org/10.1007/978-3-642-02490-0_109
Pracoviště: Katedra elektromagnetického pole
Anotace:
This work describes the basic steps of a novel approach to weather classification by remote and local atmosphere sensing. Atmospheric data on the troposphere are gathered by 10 GHz radio links and a number of meteorological sensors. Classification is performed by artificial neural networks (ANN) and is crucial for further processing, because of the different RF propagation influences under a variety of weather conditions. Reasons for using ANN compared to other means of classification are discussed. Differences in the size and number of hidden layers of back-propagation networks used are discussed. Different learning sets of measured data and their construction are also evaluated.

First Results from Remote Sensing of the Atmosphere Using Artificial Neural Networks

Autoři: Ing. Martin Mudroch, Ph.D., prof. Ing. Pavel Pechač, Ph.D., Grábner, M., Kvičera, V.
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 1356-1359. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
This document presents first results from remote sensing of atmosphere using data gathered within an unique experiment combined with artificial neural network data processing. Extended methods of data evaluation are presented and its suitability for refractivity height profiles estimations is also shown.

Joint Probability Distribution and Correlation of Multipath Signals on 10 GHz Fixed Terrestrial Link

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 3740-3743. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
A multi-receiver propagation experiment is described in which received signal level fluctuations are measured at different heights on the receiver site of the 50 km long terrestrial path operating in the 10 GHz band. Five receivers are installed on the mast in the heights of 51.5, 61.1, 90.0, 119.9 and 145.5 m above the ground. Multipath fading events due to atmospheric refraction are observed and analysed. Annual joint statistics and correlation characteristics of the received signals in different heights are obtained from the first year data.

Measurement of Building Penetration Loss as a Function of the Elevation Angle and Floor Level

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 3463-3467. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper addresses the outdoor-to-indoor penetration loss as a function of the elevation angle and the floor level. The study is based on narrowband path loss measurement trials in an urban area using a small remote-controlled airship. The building penetration loss measurements were performed at 2.0 GHz and 3.5 GHz. A detailed analysis of the penetration loss as a function of the floor level is presented. Two scenarios - two multi-storey buildings - in the city of Prague were selected for the study.

Quasioptical Beam Propagation for Remote Sensing

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: IGARSS 2009 (2009 IEEE International Geoscience and Remote Sensing Symposium) Proceedings. Bryan: Conference Management Services, Inc., 2009. pp. 742-744. ISBN 978-1-4244-3395-7.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
A development of millimeter waveband indoor sensors has brought new research challenges especially with respect to the sensing within complex environments. To investigate the propagation aspects for these systems the quasioptical approaches including Gaussian beams of basic and higher orders can be utilized. Difference between conventional and Gaussian beam based models can be significant especially for remote sensing systems being deployed within indoor scenarios. The paper discusses the advantages and drawback of these simulation approaches, based on measurement and analyses of electromagnetic wave propagation.

Route Diversity Simulations in Multi-HAP Networks during Heavy Rainstorms

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 278-280. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
Route diversity is one of the available techniques to improve system availability of High Altitude Platform (HAP) networks during rainstorms. Route diversity was simulated in both time and space using radar rainfall data. The propagation aspects of HAP service as observed at the user ground station were analyzed based on their analogy to terrestrial point-to-multipoint systems.

The use of the Fabry-Perot interferometer for high resolution microwave spectroscopy

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Černý, P., Piksa, P., Ing. Tomáš Kořínek, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc., Varga, J., Koubek, J., Urban, Š.
Publikace: Journal of Molecular Spectroscopy. 2009, 256(1), 141-145. ISSN 0022-2852.
Rok: 2009

DOI: 10.1016/j.jms.2009.03.015
Odkaz: https://doi.org/10.1016/j.jms.2009.03.015
Pracoviště: Katedra elektromagnetického pole
Anotace:
A simple Fabry-Perot interferometer was used for measurements of microwave spectra. Both basic experimental arrangements, absorption and emission, were tested on the rotational spectra of acetonitrile. The interferometric results obtained were compared with the spectra measured using a standard high resolution microwave spectrometer.

Time Domain Detection of Interference Signals using Ultra Wideband Techniques

Autoři: Urban, R., prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EuCAP 2009 - 3rd European Conference on Antennas and Propagation. New York: IEEE, 2009. pp. 178-181. ISBN 978-1-4244-4753-4.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
A specific time domain approach to the detection of services within a particular channel using ultra wideband pulse techniques is introduced. The investigation is based on measurements and simulations of several ultra wideband pulses propagating and reflecting within a particular scenario and received together with an interfered narrowband signal.

Validation of Route Diversity Schemes of Two Joint HAP LInks

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Proceesings of The 2009 International Symposium on Antennas and Propagation (ISAP 2009). Bangkok: King Mongkut's University of Technology North Bangkok (KMUTNB), 2009. pp. 520-523. ISBN 978-974-235-465-7.
Rok: 2009

Pracoviště: Katedra elektromagnetického pole
Anotace:
High Altitude Platforms (HAP) can bring a possibility of a very fast additional coverage e.g. in the case of catastrophes, when existing networks collapse, or could be utilised as alternatives to satellite or terrestrial systems. In this paper electromagnetic wave propagation aspects for HAP systems are discussed. In the first part, atmospheric gas attenuation for inter-HAP links is determined. Next part of the paper deals with the influence of rain on millimetre wavelength links between user stations and High Altitude Platform. Typical route diversity scheme given by the recommendation ITU-R P. 618 used for satellite links cannot be accurately applied. Based on simulation results HAPs are analyzed and particular corrections for the Czech Republic are proposed.

A Study of Gas and Rain Propagation Effects at 48GHz for HAP Scenarios

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Piksa, P., prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EURASIP Journal on Wireless Communications and Networking. 2008, 5(1), 1-7. ISSN 1687-1499.
Rok: 2008

DOI: 10.1155/2008/734216
Odkaz: https://doi.org/10.1155/2008/734216
Pracoviště: Katedra elektromagnetického pole
Anotace:
The atmosphere and rainfall significantly limit the performance of millimeter wave links and this has to be taken into account, particularly, during planning of high altitude platform (HAP) networks. This paper presents results from the measurement and simulation of these phenomena. A simulation tool from our previous analyses of terrestrial point-to-multipoint systems has been modified for HAP systems. Based on a rainfall radar database and gas attenuation characteristics as measured by a Fabry-Perot resonator, the performance of a simple link, two-branch diversity links, and more complicated HAP scenarios are discussed.

An Experimental Study of the Lowest Troposphere Layers at 10 GHz - First Results

Autoři: Ing. Martin Mudroch, Ph.D., Grábner, P., Kvičera, V., doc. Ing. Přemysl Hudec, CSc., Bedrna, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 14th Conference on Microwave Techniques COMITE 2008. Praha: Československá sekce IEEE, 2008. pp. 73-76. ISBN 978-1-4244-2137-4.
Rok: 2008

DOI: 10.1109/COMITE.2008.4569896
Odkaz: https://doi.org/10.1109/COMITE.2008.4569896
Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper introduces an extensive innovative experiment for both local and remote combined sensing of the troposphere. The experiment is based on a unique set of mutually linked, time-space dependent, synchronized radio-electrical and radio-meteorological measurements. The results for the first two months of operation are also presented and discussed.

Application of Realistic Propagation Prediction Models for HAP 3.5G Systems in Urban Environment

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: ISAP 2008 Proceedings. Tokyo: IEICE, Institute of Electronics, Information and Communication Engineers, 2008. pp. 786-789. ISBN 978-986-84787-0-1.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with system level simulations of 3.5G networks using realistic propagation prediction models in build-up areas instead of the simple FSL model, widely used for simulations of HAP 3G systems. The supposed impact of realistic models on an uplink quality of coverage of HAP 3.5G systems is presented. The 3G networks provided via HAPS can play an important role for providing voice and data services in urban areas during disasters or could be an alternative for providing wireless services in developing countries, especially in case of High Speed Data Access (HSPA) evolution of 3G networks.

Coexistence of Terrestrial and HAP 3G Networks during Disaster Scenarios

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2008, 2008(4), 1-7. ISSN 1210-2512.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to show the possible coexistence of an HAP and a terrestrial component of 3G networks at a single carrier frequency. The main goal is to compare the basic parameters of terrestrial and HAP component 3G networks modeled in suburban (macrocell) and urban (macro/microcell) areas and to demonstrate the way they impact on each other. This study should present what we assume are the better capabilities of HAP 3G networks compared to their terrestrial counterparts. The parameters of the HAP and terrestrial component of 3G networks, were the terrestrial cells to be disabled during disasters, are also presented.

Elevation Dependent Shadowing Model for Mobile Communications via High Altitude Platforms in Built-Up Areas

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2008, 56(4), 1078-1084. ISSN 0018-926X.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
An empirical propagation prediction model is described for mobile communications from high altitude platforms (HAPs) in different types of built-up areas. The target frequencies are selected from the 2 to 6 GHz frequency band prospective for 3G and 4G mobile systems. The simulation of the urban environment is based on a statistical approach. Additional shadowing path loss is calculated using the uniform theory of diffraction for NLOS conditions. The shadowing path loss is defined as a function of the elevation angle. The results of the empirical model developed for idealized conditions are verified by measurements taken from a remote-controlled airship in different types of urban environment. The HAP elevation dependent shadowing model is easy to implement and can be used for realistic planning and simulations of mobile networks provided via HAPs in built-up areas.

Higher Modes of Sub-millimetric Fabry-Perot Resonator

Autoři: Piksa, P., prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: URSI - XXIX General Assembly - Proceedings. Tokyo: URSI, 2008. ISSN 0074-9516.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
The atmospheric attenuation is very often neglected within propagation of electromagnetic waves at lower frequencies but it has significant effects on millimeter, sub-millimeter and terahertz links. Based on a previous measurement campaign, this paper presents results from simulation of the Fabry-Perot resonator utilized for the gas attenuation measurements. The gas attenuation has proved to be highly influenced by higher modes arising from the resonator cavity. Their dependence on particular measurement deployment is analyzed in the paper.

Multipath Signal Variation Characteristics of 10 GHz Fixed Terrestrial Multi-Receiver Path

Autoři: Grábner, M., Kvičera, V., prof. Ing. Pavel Pechač, Ph.D., Valtr, P.
Publikace: ISAP 2008 Proceedings. Tokyo: IEICE, Institute of Electronics, Information and Communication Engineers, 2008. pp. 935-938. ISBN 978-986-84787-0-1.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
First results of the experimental study of multipath fading characteristics on the fixed terrestrial link were presented. Empirical probability density function of received signal and of the signal variation rate were given.

Penetration Loss Measurement and Modeling for HAP Mobile Systems in Urban Environment

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: EURASIP Journal on Wireless Communications and Networking. 2008, 2008(2), 1-7. ISSN 1687-1499.
Rok: 2008

DOI: 10.1155/2008/543290
Odkaz: https://doi.org/10.1155/2008/543290
Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to present the results of a measurement campaign focused on the evaluation of penetration loss into buildings in an urban area as a function of the elevation angle. An empirical model to predict penetration loss into buildings is developed based on measured data obtained using a remote-controlled airship. The impact on penetration loss of different buildings and user positions within the buildings is presented. The measured data are evaluated as a function of the elevation angle. The measurement campaign was carried out at 2.0 GHz and 3.5GHz carrier frequencies, representing the frequency band for high altitude platform third-generation mobile systems and, potentially, next generation mobile systems, mobile WiMAX, for example, the new penetration loss model can be used for system performance simulations and coverage planning.

Platformy ve velkých výškách a mobilní komunikační systémy

Autoři: prof. Ing. Pavel Pechač, Ph.D., Holiš, J.
Publikace: Satelitní komunikace - 29. seminář. Praha: Česká elektrotechnická společnost, 2008. pp. 22-27. ISBN 978-80-02-02067-7.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
Příspěvek se zabývá použitím platforem ve velkých výškách pro mobilní komunikační systémy. Jsou prezentovány výsledky vědeckovýzkumné činnosti FEL ČVUT v Praze v této oblasti.

PMP System Analyzing Based on Rain Spatial Model

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Proceedings of Mosharaka International Conference on Communications Networking & Information Technology. Amman: Jordan University of Science and Technology Faculty of Engineering, 2008. pp. 64-67. ISBN 978-9957-486-04-4.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
Signal propagation at frequencies above 10 GHz suffers from significant attenuation due to rain. Given the non-uniform spatial distribution of the rain rate, the route diversity concept can be utilized to plan point-to-multipoint (PMP) systems. Outages within systems were studied using space-time simulations of PMP under specific conditions. PMP system performance was analyzed based on the rain spatial parameter and on a derived system outage improvement probability.

Provision of 3G Mobile Services in Sparsely Populated Areas Using High Altitude Platforms

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2008, 17(1), 43-49. ISSN 1210-2512.
Rok: 2008

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with the application of High Altitude Platforms for the provision of third generation mobile services in sparsely-populated areas or in developing countries. It foruces on the behavior of large cells provided via a multiple HAP deployment and shows the possibilities of using small cells located inside these large cells to serve hot-spot areas. The impact of the different types of HAP antenna masks and their adjustment on cell capacity and the quality of coverage is presented. The main parameter of the antenna radiation pattern under investigation is the power roll-off at the cell edge. Optimal values of this parameter are presented for different scenarios. Simulations of system level parameters were based on an iteration lopps approach.

A Radiowave Propagation Study In Urban Environment Using The Fourier Split-Step Parabolic Equation

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: Proceeding of the 2nd European Conference on Antennas and Propagation. Stevenage, Herts: The Institution of Engineering and Technology (IET), 2007. ISBN 978-0-86341-842-6.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents the application of the split-step Fourier transform parabolic equation to propagation modelling in urban scenarios with respect to complex boundary conditions modelling. Impedance boundary modelling is achieved using a domain decomposition algorithm enabling individual impedance boundaries to be treated using mixed sine and cosine transform. Simulation results for several twodimensional scenarios are shown. The results obtained are compared with geometrical optics/UTD.

Analysis of Propagation Effects for HAP 3G Networks in Urban Areas

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceeding of the 2nd European Conference on Antennas and Propagation. Stevenage, Herts: The Institution of Engineering and Technology (IET), 2007. ISBN 978-0-86341-842-6.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to present opportunities afforded by a small remote controlled airship for propagation measurements in basic urban scenarios. Experiments were proposed in the 2.0 - 6.0 GHz frequency bands. An example of measured data at the 2.0 GHz is presented. The goal is to obtain experimental data that can be used for planning of mobile communication systems delivered via High Altitude Platforms. The impact of shadowing effects of buildings and the penetration loss into the buildings is shown.

Application of High Altitude Platforms to the Provision of 3G Mobile Services in Sparsely-Populated areas

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 2007 International Symposium on Antennas and Propagation. Tokyo: The Institute of Electronics, Information and Communication Engineers, 2007. pp. 466-469. ISBN 978-4-88552-223-9.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with the application of High Altitude Platform Stations (HAPS) to the provision of third generation mobile services in sparsely-populated areas. The coverage of extensive and sparsely populated areas by 3G mobile network signals is complicated and extremely expensive. A solution to this problem could be the use of HAPS, which appear to be very prospective, and not only for developing countries. High Altitude Platforms (HAPs), situated in the stratosphere at an altitude ranging from 17 to 22 km [1], offer many advantages when compared to terrestrial base stations, such as a large area of coverage and no shadowing for high elevation angles. This paper focuses on the behaviour of large cells provided via a multiple HAP deployment and shows the possibilities of using small cells located inside these large cells to serve hot spot areas. The impact of the antenna power roll-off at the cell edge on cell capacity and the quality of coverage will be presented.

Domain Decomposition Algorithm for Complex Boundary Modeling using the Fourier Split-Step Parabolic Equation

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Antennas and Wireless Propagation Letters. 2007, 6(1), 152-155. ISSN 1536-1225.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper addresses the use of parabolic equation in radiowave propagation problems involving impedance-boundary modeling. The Fourier split-step technique for solving the parabolic equation provides numerical efficiency but lacks the ability to represent complex boundary conditions. A method that makes use of the domain decomposition technique to solve two-dimensional problems of impedance-boundary modeling using the Fourier split-step technique is introduced. A test case, using an urban scenario represented by buildings with various electrical parameters, was used to validate the results given by the method with results obtained by geometrical optics.

Gas Attenutation Measurement by Utilization of Fabry-Perot Resonator

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Piksa, P., Černý, P., prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceeding of the 2nd European Conference on Antennas and Propagation. Stevenage, Herts: The Institution of Engineering and Technology (IET), 2007. ISBN 978-0-86341-842-6.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
The atmosphere significantly limits the performance of millimetre-wave and terahertz systems. The aim of this paper is to introduce a development and an improvement of Fabry-Perot resonator utilized especially for gas attenuation measurements. The measurement setup and results from simulations and laboratory measurements performed via Fabry-Perot resonator are discussed as well.

Implementation Issues of the Matched Field Processing Method of Refractivity Structure Sounding

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., Grábner, M.
Publikace: Proceeding of the 2nd European Conference on Antennas and Propagation. Stevenage, Herts: The Institution of Engineering and Technology (IET), 2007. ISBN 978-0-86341-842-6.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
As the atmospheric conditions, expressed in terms of radio refractivity can considerably influence the performance of radio communication links and radar systems, there is a need for reliable prediction of refractivity structure in the košer atmosphere. The paper is focused on the remote sensing of refractivity structure in the lower atmosphere using Matched Field Processing method. The paper discusses the proper radio link set-up with respect to improving the performance of radio refractivity estimation using remote the sensing technique.

Influence of Rain Event Area on PMP System Performance

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceeding of the 2nd European Conference on Antennas and Propagation. Stevenage, Herts: The Institution of Engineering and Technology (IET), 2007. ISBN 978-0-86341-842-6.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper, the influence of the area size covered by rain on the efficiency of route diversity applied in systems during the rain event is analyzed for specific areas with a range of dimensions, from small areas up to those with diameters of 150 km x 150 km. The derivation of rain spatial parameter statistics and their validity in terms of the size of the investigated area are discussed.

Measurement of Propagation Effects from Low Altitude Airship in Urban Area Appplicable for Stratospheric Platforms

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 2007 International Symposium on Antennas and Propagation. Tokyo: The Institute of Electronics, Information and Communication Engineers, 2007. pp. 462-465. ISBN 978-4-88552-223-9.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with trial focused on a path loss measurement in urban area using a low altitude airship. Experiments were proposed at 2.0 GHz, 3.5 GHz and 5.5 GHz frequencies representing the frequency band for 3G, mobile WiMAX and WiMAX systems. The trial was aimed at rooftop diffraction loss and penetration loss measurement. The goal was to obtain experimental data that can be used to planning of communication systems delivered via High Altitude Platforms (HAPs) [1].

Providing of Third Generation Mobile Service via High Altitude Platforms

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D., Grace, D.
Publikace: Proceedings of Workshop 2007. Praha: České vysoké učení technické v Praze, 2007. pp. 218-219. ISBN 978-80-01-03667-9.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
The third generation mobile system UMTS (Universal Mobile Telecommunications System), especially supplemented with High-speed Downlink Packet Access (HSDPA), should fulfill the increasing requirements for high-speed mobile data communication. The quick deployment of UMTS networks is, among others, limited by coverage possibilities. This is dominant in suburban and rural areas. High Altitude Platforms (HAPs) will be situated in the stratosphere at an altitude from 17 to 22 km and could be used as an alternative to a terrestrial component for third generation mobile networks UMTS or could be a complementary element of terrestrial networks in case of providing telecommunication and data services in sparsely populated areas such as in Africa, during disasters, terrorist attacks, etc.

Septum Horn Antennas at 47/48 GHz for High Altitude Platform Stations

Autoři: Hradecký, Z., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc., Galuščák, R.
Publikace: Proceeding of the 2nd European Conference on Antennas and Propagation. Stevenage, Herts: The Institution of Engineering and Technology (IET), 2007. ISBN 978-0-86341-842-6.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
A design of a septum horn antenna for frequency band 47.0-48.5 GHz (based on the studies and designs at 1.3 GHz and 2.4 GHz) left and right polarized is presented. A 20 dBi gain septum horn antenna was developed and manufactured. Calculated data (radiation pattern, beamwidth, sidelobes suppression, gain and VSWR) were compared with measured data.

UHF Propagation in Caves and Subterranean Galleries

Autoři: Rak, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2007, 55(4), 1134-1138. ISSN 0018-926X.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
An experimental study is described on the natural propagation of UHF band radio waves in straight subterranean galleries. An extensive measurement project took place in five underground localities and, based on the experimental data, an empirical model of radio wave transmission was derived. The model was calibrated according to the measurement data and compared with the theoretical waveguide approach to propagation prediction. The presented results can be used for the practical planning of wireless communications in speleology applications and as an experimental basis for further theroetical works.

Základy šíření vln pro plánování pozemních rádiových spojů

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Stanislav Zvánovec, Ph.D.,
Publikace: Praha: BEN - technická literatura, 2007. BEN. ISBN 978-80-7300-223-7.
Rok: 2007

Pracoviště: Katedra elektromagnetického pole
Anotace:
Kniha je věnována základům problematiky šíření elektromagnetických vln pro pozemní rádiové komunikační systémy. Je zde vysvětlena fyzikální podstata šíření vln v atmosféře, jenž rádiové spoje ovlivňuje zásadním způsobem. Podrobně jsou dále rozebrány i jednotlivé vlivy troposféry a ionosféry. Jsou popsány i techniky používané k modelování šíření vln pro potřeby návrhu jednotlivých rádiových služeb z širokého kmitočtového spektra.

Analytic Tropospheric Ray-tracing Model for Constant Refractivity Gradient Profiles

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of The European Conference on Antennas and Propagation: EuCAP 2006. Noordwijk: ESA Publications Division, 2006. ISSN 1609-042X. ISBN 92-9092-937-5.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
Prediction methods in tropospheric electromagnetic wave propagation primarily rely on ray-tracing and parabolic equation. While the parabolic equation approach represents a full-wave method of wave equation solution, ray-tracing methods make use of the ray-concept taken from physical optics. Although ray-tracing is not capable of giving exact field strength/phase in general cases, it does provide a useful tool for illustrating atmospheric refraction effects. The main advantage of the ray-tracing concept lies in the relative simplicity of its implementation. The aim of this paper is to introduce an analytic ray-based method of field amplitude/phase computation to consider the refractive properties of the atmosphere, represented by a refractive index gradient.

Cell Capacity of UMTS Provided via HAP Stations Using Elliptical and Circular Beam Antennas in Urban and Suburban Areas

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings in COST 297 WGI Meeting. York: COST Office, 2006.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with an application of High Altitude Platform stations as an alternative of providing third generation mobile services in suburban and urban areas. This work is focused on the impact of circular and elliptical beam antennas on other-to-own cell interference ratio and capacity, respectively. Results of system level simulations of UMTS mobile networks operating in WCDMA FDD mode are shown in different simulative scenarios in suburban and urban environments.

Dependence of Area-Averaged Rain Rate on PMP System Coverage Planning

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., Kvičera, V., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Proceedings of the International Symposium on Antennas and Propagation - ISAP 2006. India: Research Publishing Services, 2006. ISBN 81-903170-8-3.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper, area-averaged rain rate calculation using the ITU-R statistical model is discussed and its accuracy investigated. The influence of its proper determination on the coverage planning of PMP systems is revealed. Moreover, a model modification which better fits the local conditions prevailing in the Czech Republic is provided.

Education in Antennas, Wave Propagation and Microwaves

Autoři: prof. Ing. Miloš Mazánek, CSc., doc. Ing. Milan Polívka, Ph.D., Černý, P., doc. Ing. Pavel Hazdra, Ph.D., Piksa, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Automatika. 2006, 47(3-4), 133-139. ISSN 0005-1144.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper is focused on teaching of "applied microwaves". Attentions is turned to antennas, but the same structure of education process is possible to apply for e.g. radio-wave propagation, microwaves, EMC, and other "electromagnetic topics" in their whole. The structure of the education is based on the appropriate amount of the theory followed by the computer simulations, the theoretical and engineering design and development, the measurement and final evaluation, which acts as the feedback between the initial goals and the final results. Important role of laboratory experiments based on flexible experimental set-ups is introduced and the possibility of distant (internet) laboratory excess is mentioned.

Measurement of Shielding Effectiveness of Small Enclosures

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., doc. Ing. Pavel Hazdra, Ph.D., Ing. Tomáš Kořínek, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: EMC Europe 2006 - International Symposium on Electromagnetic Compatibility - Proceedings 1, 2. Barcelona: Technical University of Catalonia, 2006. pp. 249-252. ISBN 84-689-9440-5.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
The evaluation of the Shielding Effectiveness (SE) brings great challenges from the EMC measurement point of view. Particularly in the case of measurement of small enclosures, many different approaches can be used. Therefore, based on an extensive measurement campaign, various aspects of measurement of the shielding effectiveness of small metallic enclosures were investigated. Significant results of this campaign are discussed in this paper.

Measurement Trials in the 3G and Millimetre Frequency Bands using a Low Altitude Airship

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D., Ing. Tomáš Kořínek, Ph.D., doc. Ing. Přemysl Hudec, CSc., Valtr, P., Kusnir, L., Houska, V., Kvičera, V., Grábner, M.
Publikace: Proceedings in First COST 297 - HAPCOS Workshop. York: COST Office, 2006.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to introduce options for measurements conducted at the CTU Prague using a low altitude airship. Experiments were proposed in the 3G and millimetre frequency bands. An example of measured data at the 2 GHz frequency is presented. An overview of planned experimental work is given. The goal is to obtain experimental data that can be used to plan communication systems delivered via High Altitude Platforms (HAPs).

On the Proper Utilization of Site Diversity Mechanism in Millimeter-Wave Band PMP Systems

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of The European Conference on Antennas and Propagation: EuCAP 2006. Noordwijk: ESA Publications Division, 2006. ISSN 1609-042X. ISBN 92-9092-937-5.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper the analytical study of a Point-to-Multipoint (PMP) system behavior during rainstorms is discussed. The proper utilization of the site diversity mechanism for two diversity links as well as in the complex point-to-multipoint system scenario is investigated. The yield of the site diversity utilization in terms of link lengths, angular separation and rain parameters is presented.

Parametric Study of Coaxial Radiating Cables

Autoři: Vrba, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of The European Conference on Antennas and Propagation: EuCAP 2006. Noordwijk: ESA Publications Division, 2006. ISSN 1609-042X. ISBN 92-9092-937-5.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
A radiating cable is a coaxial cable with specially designed slots in its outer conductor. The electromagnetic field traveling inside the cable is through these slots coupled outside and by reciprocity the field outside the cable influences the inner field. The amount of the radiated energy is determined by the dimensions, shape and number of slots. The frequency band is dependent on the positions and orientation of the slots. In this article a parametric study of one particular coaxial radiating cable with different slot configurations using a full-wave electromagnetic simulator CST Microwave Studio [1] is presented. The main parameters such as frequency bandwidth and field distribution along the cable are investigated based on dimensions and positions of the slots.

Propagation Prediction for High Altitude Platforms in 3G Frequency Band

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceeding of the 9th International Symposium Wireless Personal Multimedia Communications. Akasaka, Minato-ku, Tokyo: WPMC Secretariat, c/o ILCC Co. Ltd., Fukuyoshizaka Building, 2006. pp. 1219-1221. ISSN 1347-6890.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to introduce propagation prediction methods for High Altitude Platform stations (HAPs) providing the third generation mobile services in suburban and especially in urban areas. Methods of the propagation prediction in urban environment based on ITU-R statistical model describing building deployments and based on Uniform Theory of Diffraction will be shown. The probabilities of both Line of Sight connections in streets and additional path losses due to rooftop diffraction will be presented.

Rain Spatial Classification for Availability Studies of Point-to-Multipoint Systems

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Antennas and Propagation. 2006, 54(12), 3789-3796. ISSN 0018-926X.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
A new approach to rain spatial classification according to its impact on system performance is proposed in the paper, using a single rainfall spatial parameter. The work is based on extensive simulation of point-to-multipoint systems using rainfall radar data.

Simulation of UMTS Networks provided via HAP Stations Using Elliptical and Circular Beam Antennas in Urban and Suburban Areas

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceeding of the 9th International Symposium Wireless Personal Multimedia Communications. Akasaka, Minato-ku, Tokyo: WPMC Secretariat, c/o ILCC Co. Ltd., Fukuyoshizaka Building, 2006. pp. 348-351. ISSN 1347-6890.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with an application of High Altitude Platform stations as an alternative of providing third generation mobile services in suburban and urban areas. It is focused on an impact of circular and elliptical beam antennas on other-to-own cell interference ratio and cell capacity, respectively. Results of system level simulations of UMTS mobile networks operating in WCDMA FDD mode are shown in different simulative scenarios in suburban and urban environments.

Šíření vln v zástavbě - modely pro plánování mobilních rádiových systémů

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Praha: BEN - technická literatura, 2006. ISBN 80-7300-186-1.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
Monografie poskytuje v přehledné a praktické formě znalosti a výpočetní nástroje pro modelování šíření rádiových vln v zástavbě, tedy vně i uvnitř budov v městském prostředí a plánování bezdrátových komunikačních sítí. Jsou zde popsány konkrétní modely šíření elektromagnetické vlny (signálu) k predikci prostorového rozložení úrovně signálu pro potřeby implementace rádiové buňkové sítě v dané lokalitě, tedy pro plánování pokrytí, určení interferencí atd. Výběr modelů a některé jejich modifikace, parametry a způsoby implementace vycházejí ze zkušeností a vědeckovýzkumné šinnosti autora a jeho kolegů na ČVUT FEL v Praze, katedře elektromagnetického pole.

The Influence of Building Material Humidity on Wedge Diffraction

Autoři: Valtr, P., Kučera, J., Bártík, H., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of The European Conference on Antennas and Propagation: EuCAP 2006. Noordwijk: ESA Publications Division, 2006. ISSN 1609-042X. ISBN 92-9092-937-5.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of the paper is to show the influence of humidity contained in real building materials on diffraction part of the field in the vicinity of a wedgeshaped obstacle. Field measurement around both dry and wet wedge formed by real building material was performed to get an idea what the influence of water content of the building material is on wedge diffraction. The measured results are compared with theoretical prediction by Uniform Theory of Diffraction. The results can be used for improvement of propagation prediction models in urban areas.

The Optimization of Antenna Power Roll-off for High Altitude Platform WCDMA Systems

Autoři: Holiš, J., Grace, D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings in First COST 297 - HAPCOS Workshop. York: COST Office, 2006.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with the results of a collaboration between the Czech Technical University in Prague and the University of York within COST Action 297 on the provision of 3G mobile services using High Altitude Platform Stations. This contribution focuses on the impact of antenna radiation patterns on the characteristics of UMTS systems provided via a single HAP. Fundamental parameters of antenna radiation pattern are shown at the main lobe power roll-off and side lobe level. The possibilities of applying circular and elliptical beam antennas are introduced.

Wave Propagation Simulations at 48 GHz for HAPs Using Rainfall Radar Data

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings in First COST 297 - HAPCOS Workshop. York: COST Office, 2006.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper presents the concept of site-specific simulations of multiple High Altitude Platform (HAP) system performance during specific rain events. The concept has been adopted from investigations of terrestrial point-to-multipoint systems operating in millimetre frequency bands. A simulation tool has been developed. Based on the radar rainfall database, various aspects of system performance such as site diversity can be studied using the simulation tool.

Základní problémy šíření elektromagnetických vln

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Šíření elektromagnetických vln. Praha: Česká elektrotechnická společnost, 2006. pp. 2-5. ISBN 80-02-01865-6.
Rok: 2006

Pracoviště: Katedra elektromagnetického pole
Anotace:
Příspěvek přináší přehled problematiky šíření rádiových vln v zemské atmosféře a ukazuje některé problémy při modelování šíření vln pro potřeby plánování rádiových systémů.

Education in Antennas, Wave Propagation and Microwave Techniques

Autoři: prof. Ing. Miloš Mazánek, CSc., doc. Ing. Milan Polívka, Ph.D., Černý, P., Piksa, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: ICECom 2005 - Conference Proceedings 18th International Conference on Applied Electromagneics and Communications. Dubrovnik: IEEE Croatia Section, 2005. pp. 417-420. ISBN 953-6037-44-0.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper is focused on teachnig "applied microwaves". Attention is turned to antennas, wave propagation, microwaves and EMC. The structure of the education based on the theory followed by the computer simulations is described. A mutual cohesion between engineering, design, numerical methods, CAD is mentioned.

Effective Propagation Prediction in Urban Microcells

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of WPMC´05 - International Symposium of Wireless Personal Multimedia Communications. Aalborg: Aalborg University, 2005. pp. 398-401. ISSN 0908-1224. ISBN 87-90834-79-8.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to introduce an effective technique of path loss calculations in microcells based on Berg's Recursive Model. The main benefit of this propagation prediction method is the input equirement in the form of a simple city plan - an ordinary bitmap. Another advantage of this approach is the computing speed of the developed software tool.

Effects of Rain Rate Spatial Distribution on Pont-to-Multipoint Systems

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings - ISAP 2005. Seoul: Korea Institute of Electromagnetic Engineering and Society (KIEES), 2005. pp. 1197-1200. ISBN 89-86522-76-4.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this article the analysis of the statistical variations in spatial organization of precipitation and its influence on point-to-multipoint systems is presented.

Investigation of Significant Uncertainties in EMC Measurement

Autoři: Valtr, P., prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: The 13th Conference on Microwave Techniques - COMITE 2005. Praha: IEEE Czechoslovakia Section, 2005. pp. 151-154. ISBN 80-86582-16-7.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper describes some aspects of determination of uncertainty in EMC measurements. Basic outline of the resulting measurement uncertainty range is presented. The main aim is to investigate the most significant components of the total uncertainty - imperfections due to the antenna factor of a receiving antenna and site imperfection of a measurement place.

Measurement of a Shielding Effectiveness of Relatively Small Metallic Enclosures

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D., doc. Ing. Pavel Hazdra, Ph.D., doc. Ing. Vítězslav Pankrác, CSc.,
Publikace: Proceedings - ISAP 2005. Seoul: Korea Institute of Electromagnetic Engineering and Society (KIEES), 2005. pp. 913-916. ISBN 89-86522-76-4.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Paper presents several results of the study and experimental verification of a shielding effectiveness of relatively small metallic enclosures, which operate above the first resonance. There is no standard for measurement and therefore different aspects of measurement and methodology are discussed. Relative size, volume, quality factor of the enclosure, position, radiator type, reciprocity etc. are discussed.

Microwave System for the Detection and Localization of Mobile Phones in Large Buildings

Autoři: doc. Ing. Přemysl Hudec, CSc., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Transactions on Microwave Theory and Techniques. 2005, 53(6), 2235-2239. ISSN 0018-9480.
Rok: 2005

DOI: 10.1109/TMTT.2005.848750
Odkaz: https://doi.org/10.1109/TMTT.2005.848750
Pracoviště: Katedra elektromagnetického pole
Anotace:
A novel monitoring system for the detection and localization of mobile (cellular) phones in large buildings based on a matrix of microwave sensors has been designed and practically employed. The system enables detection of all active mobile services and ensures very high immunity against all other radio signals. The designed antennas, system structure and signal processing provide high probability of correct localization of the transmitting mobile phone.

Millimeter-wave Systems Outage Improvements During Rain Events

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2005 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2005. pp. 231-234. ISBN 80-214-2904-6.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
The motivation of this work is to offer a simple way to evaluate possibilities of the site diversity employment for specific scenarios in millimeter-wave band. Outage improvement has been studied using space-time simulations of a point-to-multipoint system in a specific area under a specific rain conditions. System outage improvement probability was derived as a function of the rain fade margin, angle separation and distances hubs. Some of the simulation results at 42 GHz are presented as well.

Novel Method of Vertical Refractivity Profile Estimation using Angle of Arrival Spetra

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings - XXVIIIth General Assembly of International Union Radio Science (URSI). Ghent: URSI, 2005.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Refractivity profile variation in lower part of the atmosphere is one of the aspects that influences long-distance terrestrial electromagnetic wave propagation and consequently performance of communication systems. Possibilities of remote sensing of refractivity profiles using field measurement at a receiver site of a terrestrial point-to-point link in terms of angle of arrival (AoA) spectra are discussed here. Models of refractivity profile are introduced to improve the estimation for various refractivity profiles.

Radiated Near-Field Measurement - Vegetation Scattering

Autoři: prof. Ing. Pavel Pechač, Ph.D., Lédl, P., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Proceedings of the International Conference on Electromagnetic Near-Field Characterization and Imaging. Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2005. pp. 187-192. ISBN 84-95999-72-2.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Power balance and fading statistics are very important issues for advanced point-to-multipoint wideband communication systems operating in millimeter waveband. Since the typical environment is an urban and suburban area a vegetation blockage is one of the performance limiting factors. While the average attenuation caused by trees is dealt with for many years there are not many resources concerning the dynamics effects caused by the vegetation blockage - fast fading statistics, etc. The goal of the presented laboratory experiment was to define basic parameters of a theoretical model. To obtain well defined conditions a radiated near-field scattered by a tree under test was measured using a near-field scanner at 38 GHz. The first phase, measurement of the co-polar field component in a 2D reception plane for various tree types and wind conditions, is introduced. The measurement data were used for the modeling of dynamic effects caused by vegetation obstacles.

Rain Dependant Site Diversity Outage Improvements Statistics for Systems Working in Millimeter-Wave Band

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Proceedings - XXVIIIth General Assembly of International Union Radio Science (URSI). Ghent: URSI, 2005.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
The signal propagation at the frequencies above 10 GHz suffers from significant attenuation due to rain, which in case of point-to-multipoint systems is unlikely to be compensated for by available fade margin alone. For this reason and especially thanks to the non-uniform spatial distribution of the rain rate, it is suitable to utilize site diversity concept during planning of point-to-multipoint wireless systems. A database of radar data for numerous types of rain events has been established to enable system testing under different conditions. Outage improvement was studied using space-time simulations of point-to-multipoint systems in a specific area under a specific rain conditions. System outage improvement probability was derived as a straightforward function of the rain fade margin, angle separation and distances of main and diversity hubs. Some of the simulation results at 42 GHz and corresponding outage improvement probability using the site diversity are presented as well.

Refractivity Height Profile Estimations Based on Radiowave Refraction Simulations

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: COST 280 - Final Workshop - Proceedings. Brussels: COST Office, 2005.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper describes possibilities of refractive index height profile estimations using field measurement at a receiver site of a terrestrial point-to-point link in terms of angle-of-arrival (AOA) spectra. Several refractivity models based on orthogonal function set are introduced to improve the estimation accuracy.

Remote Sensing of Refractivity Profile using Angle of Arrival Spectra

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2005 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2005. pp. 235-238. ISBN 80-214-2904-6.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Knowledge of refractive index height dependence enables prediction of field strength at a receiver site of the communication link. This paper presents possibilities of the refractivity estimation based on the received field in terms of angle-of-arrival (AOA) spectra.

Shielding Effectiveness Measurement Issues for Small Enclosures

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., doc. Ing. Pavel Hazdra, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: The 13th Conference on Microwave Techniques - COMITE 2005. Praha: IEEE Czechoslovakia Section, 2005. pp. 291-294. ISBN 80-86582-16-7.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Shielding Effectiveness (SE) is one of the major aspects of any EMC design process. In this paper, a detailed analysis of measurement issues of a shielding effectiveness of relatively small metallic enclosures is presented. An extensive measurement campaign has been done to investigate various aspects of measurement of the small enclosures shielding effectiveness.

Shielding Efficiency Measurement Possibilites

Autoři: Hradecký, Z., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: The 13th Conference on Microwave Techniques - COMITE 2005. Praha: IEEE Czechoslovakia Section, 2005. pp. 283-286. ISBN 80-86582-16-7.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Knowledge of shielding efficiency of plane materials like shielding panels, special paints, windows foils etc. is demanded for construction of shielded boxes, enclosures and for other applications. Shielding efficiency is possible to measure in free space or in waveguide. Measurement in free space was performed in divided anechoic chamber by wall with window there are placed measured materials. Waveguide measurement unit was specially designed and manufactured to measure the high level of shielding efficiency of thin conductive materials in the frequency band of about 400 MHz. The shielding efficiency of various materials was measured by means of both methods and the results were compared. At the end is discussion about advantages and disadvantage various methods.

Simulation of UMTS Capacity and Quality of Coferage in Urban Macro- and Microcellular Environment

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2005, 14(4), 21-26. ISSN 1210-2512.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
This paper deals with simulations of a radio interface of third generation (3G) mobile systems operating in the WCDMA FDD mode including propagation predictions in macro and microcells. In the radio network planning of 3G mobile systems, the quality of coverage and the system capacity present a common problem. Both macro and microcellular concepts are very important for implementing wireless communication systems, such as Universal Mobile Telecommunication Systems (UMTS) in dense urban areas. The aim of this paper is to introduce different impacts - selected bit rate, uplink (UL) loading, allocation and number of Nodes B, selected propagation prediction models, macro and microcellular environment - on system capacity and quality of coverage in UMTS networks. Both separated and composite simulation scenarios of macro and microcellular environments are presented. The necessity of an iteration-based simulation approach and site-specific propagation modeling in microcells is proven.

Simulation of UMTS Capacity in Microcellular Urban Environment

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D., Lédl, P.
Publikace: Proceedings of WPMC´05 - International Symposium of Wireless Personal Multimedia Communications. Aalborg: Aalborg University, 2005. pp. 1747-1750. ISSN 0908-1224. ISBN 87-90834-79-8.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is to introduce the different impacts - selected service, uplink loading, allocation and number of Node B, selected propagation prediction model - on system capacity and quality of coverage of the third generation mobile networks UMTS operating in WCDMA FDD mode in urban microcells.Microcellular environment is very important environment for wireless personal communication systems such as UMTS.

Simulations of Site Diversity Based Outage Improvements for Point-to-Multipoint Systems in Millimeter-Wave Band

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Wireless Telecommunications Symposium 2005. Piscataway: IEEE, 2005. ISBN 0-7803-8857-7.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Outage improvement was studied using space-time simulations of a PMP system in millimeter-wave bands in a specific area under a specific rain conditions. System outage improvement probability was derived as a straightforward function of the rain fade margin, angle separation and distances of main and diversity hubs. Some of the simulation results at 42 GHz and corresponding outage improvement probability using the site diversity are presented as well.

Study of UMTS in Urban Macro and Microcellular Environment

Autoři: Holiš, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: The 13th Conference on Microwave Techniques - COMITE 2005. Praha: IEEE Czechoslovakia Section, 2005. pp. 60-63. ISBN 80-86582-16-7.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Both macrocellular and microcellular concepts are very important for implementation of new wireless communication systems such as UMTS in dense urban areas. The aim of this paper is to introduce the different impacts - selected service, uplink loading, allocation and number of Nodes B, macro and micro environment - on system capacity and quality of coverage in UMTS networks operate in WCDMA FDD mode. This paper deals with the simulations of UMTS micro- and macrocellular environment as separated as composite.

The Influence of Horizontally Variable Refractive Index Height Profile on Radio Horizon Range

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: IEEE Antennas and Wireless Propagation Letters. 2005, 4(1), 489-491. ISSN 1536-1225.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
This letter addresses refraction effects, assuming a horizontally nonhomogeneous troposphere. The influence of a range-dependent refractivity profile on a terrestrial radio link is investigated in terms of radio horizon range. The results can be used for interference analysis in metropolitan wireless networks. An analytical ray-tracing approach was employed to derive formulas for the radio horizon range calculation, considering a horizontally variable refractivity height profile.

Tropospheric Refraction Modeling Using Ray-Tracing and Parabolic Equation

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2005, 14(4), 98-104. ISSN 1210-2512.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Refraction phenomena that occur in the lower atmosphere significantly influence the performance of wireless communication systems. This paper provides an overview of corresponding computational methods. Basic properties of the lower atmosphere are mentioned. Practical guidelines for radiowave propagation modeling in the lower atmosphere using ray-tracing and parabolic equation methods are given. In addition, a calculation of angle-of-arrival spectra is introduced for multipath propagation simulations.

Zobecněný přístup k měření v mikrovlnné oblasti

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D., Bártík, H., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Karel Hoffmann, CSc., doc. Ing. Pavel Hazdra, Ph.D., Hradecký, Z.
Publikace: Sdělovací technika. 2005, 2005(3), 3-6. ISSN 0036-9942.
Rok: 2005

Pracoviště: Katedra elektromagnetického pole
Anotace:
Je popsán obecný princip měření jak v časové, tak ve frekvenční oblasti a vzájemné vazby jednotlivých parametrů.

Building Electrical Parameters Estimation

Autoři: Hradecký, Z., Mikas, F., Klepal, M., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Symposium Proceedings - URSI-F 2004. Milton: URSI, 2004. pp. 55-58. ISBN 0-646-43423-3.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
An accuracy of all empirical and semi-empirical models for signal coverage prediction especially in an indoor environment significantly depends on precise input parameters. These parameters include the information on electrical material parameter (permittivity, permeability, conductivity) as well as geometry of the walls. Because the building wall structure is usually a complicated pla-parallel layered media, there is not possibility to predict these based from single frequency and only scalar measurement. Wideband - or multi-band measurement can improve the tuning of the model better to the reality. A method which helps to estimation the dielectric parameters and also wall insertion loss from such wideband measurement is introduced.

Diffraction Calculations and Measurements in Millimeter Frequency Band

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2004, 13(3), 18-21. ISSN 1210-2512.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
The paper deals with a study of diffraction on dielectric wedge (building corner) in millimeter frequency band, both theoretically and experimentally, to provide knowledge support for ray tracing/launching calculations of MWS interference issues in urban areas. The main motivation was to find balance between reasonably reliable results and necessary demands on calculation complexity and input data accuracy. Verification of Uniform Theory of Diffraction (UTD) was made both for perfectly conducting and dielectric wedge-shaped obstacle. Comparisons of theoretical results and experimental measurement at millimeter waves in anechoic chamber are presented.

Educational Support of The Course "Propagation of Electromagnetic Waves and Frequency Planning"

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Mikas, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of Workshop 2004. Praha: České vysoké učení technické v Praze, 2004. pp. 412-413. ISBN 80-01-02945-X.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
This project is focused on preparation and accomplishing of practical and experimental exercises for new course "Propagation of Electromagnetic Waves and Frequency planning". Students will be able to verify their theoretical knowledge by practical measurements of coverage signal level and other parameters of wireless local networks (WLAN) in the frequency band 2,4 GHz. These exercises will demonstrate current possibilities of computer connection to networks by this modern technology as well.

Influence of Horizontally Variable Refractive Index Height Profile on Tropospheric Refraction

Autoři: Valtr, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: CD ROM Proceedings, COST 280. Brussels: COST Office, 2004.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
Tropospheric refraction effects are discussed here, with an aim at inspecting an influence of change of refractive index profile with distance to a terrestrial millimetre link. When treating refraction effects in the troposphere, usually only height dependence of the refractive index profile is considered. However, this might not always be exactly the real situation. Situation may occur, that electromagnetic wave is exposed to range dependent refractive index height profiles as it propagates. Several examples are presented here with results in terms of received signal strength and angle of arrival. Under certain refractive index distribution the electromagnetic wave can propagate at a long distance, exceeding the optical line-of-sight distance of the terrestrial link and possibly resulting in interference effects.

Large Scale Behaviour of Multipath Fading Channels in Urban Macrocellular Environments

Autoři: Mikas, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Conference Proceedings of Radioelektronika 2004. Bratislava: Slovak University of Technology, 2004. pp. 445-448. ISBN 80-227-2017-8.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
Based on wideband measuring compaign this article describes some aspects of large scale behaviour of multipath fading channels in small urban macrocellular environments. Correct suppression of distance dependency of received signal power is also discussed.

Measurement of Diffraction on Dielectric Building Materials to Improve the Remote Sensing Data Evaluation

Autoři: prof. Ing. Miloš Mazánek, CSc., Valtr, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Symposium Proceedings - URSI-F 2004. Milton: URSI, 2004. pp. 116-125. ISBN 0-646-43423-3.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole

Modeling and Measurement of Dynamic Vegetation Effects at 38 GHz

Autoři: prof. Ing. Pavel Pechač, Ph.D., Lédl, P., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Symposium Proceedings - URSI-F 2004. Milton: URSI, 2004. pp. 147-155. ISBN 0-646-43423-3.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole

Modeling and Optimization of Heterogeneous Wireless LAN

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., Martinez, A.
Publikace: Proceedings of the 2004 60th Vehicular Technology Conference. 2004. ISBN 0-7803-8522-5.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
A sophisticated approach to automated prediction for the optimal layout and quantity of WLAN access points to achieve the desired network parameters is introduced. The algorithms were implemented in web-based software for RF planning of complete wireless local area system with multiple radio frequency technologies (IEEE 802.11a, 802.11b/g, and Bluetooth) based on mesh topology. The implemented optimization method based on Evolution Strategies offers easy specification of various network aspects and QoS requirements (hotspots of various technologies, proffered areas near Ethernet ports and power outlets, throughput, number of concurrent users, etc.). The first few months of operation and usage in many real-world scenarios have shown good performance and appropriate accuracy. The application is also able to model site-specific coverage and capacity of the wireless network using semi-empirical propagation models.

Problematika šíření vln pro systémy MWS v mm pásmu

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radiokomunikace 2004. Pardubice: UNIT, 2004. pp. 63-67.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
Multimediální bezdrátové systémy MWS (Multimedia Wireless Systems) patří mezi perspektivní systémy poskytující bezdrátovou distribuci multimediálních dat na tzv. "poslední míli" v milimetrovém pásmu. Cílem příspěvku přehledný souhrn základních aspektů plánování systémů MWS z hlediska šíření elektromagnetických vln

Shielding Efficiency Waveguide Measurements at 400 MHz

Autoři: prof. Ing. Pavel Pechač, Ph.D., Hradecký, Z., prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Proceedings of the 2004 60th Vehicular Technology Conference. 2004. ISBN 0-7803-8522-5.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
Knowledge of shielding efficiency of plane materials like shielding panels, special paints, windows foils etc. is demanded for construction of shielded boxes, enclosures and for other applications. Waveguide measurement unit was specially designed and manufactured to measure the high level of shielding efficiency of thin conductive materials in the frequency band of 40 MHz. Dynamic range of measurement up to 100 dB was reached. Shielding efficiency of various materials was measured and compared to measurements in free space. The waveguide unit development brought several advantages which had to be addressed. The main problems were caused by reflections of the inserted material under the test with high attenuation of the relatively short waveguide. Waveguide, broadband transitions design, attenuators arrangements and the material under test attachment were designed using both the simulations and experiments.

Shielding Materials Waveguide Measurement about 400 MHz

Autoři: Hradecký, Z., prof. Ing. Miloš Mazánek, CSc., prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Conference Proceedings of Radioelektronika 2004. Bratislava: Slovak University of Technology, 2004. pp. 461-464. ISBN 80-227-2017-8.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
Knowledge of shielding materials attenuation is highly demanded for construction of shielded boxes or spaces and for other applications. In the paper the measurement of shielding materials attenuation up to 100 dB is presented. The main focus is given to a design of measurement unit and demonstration of measured data.

Signal Propagation Simulation Tool for LMDS

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Conference Proceedings of Radioelektronika 2004. Bratislava: Slovak University of Technology, 2004. pp. 426-429. ISBN 80-227-2017-8.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
The deployment of newly emerging communication systems working in the millimeter-waves frequency bands are a challenge for designers also from electromagnetic waves propagation point of view. This article deals with main phenomena that affect signal propagation for Local Multipoint Distribution Systems (LMDS) at frequencies above 30 GHz. A new propagation simulation tool for LMDS is presented. Some of the simulation results are depicted as well.

Šíření elektromagnetických vln

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Stanislav Zvánovec, Ph.D., Mikas, F., Valtr, P.
Publikace: Sborník vzdělávacích a vědeckovýzkumných činností a nabídek. Praha: IEEE Czechoslovakia Section, 2004. p. 32. ISBN 80-86582-15-9.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole

Site Diversity Time-Space Simulations for LMDS

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of the 2004 60th Vehicular Technology Conference. 2004. ISBN 0-7803-8522-5.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
For point to multi-point systems working in millimeter frequency bands high reliability of the links is required. The attenuation due to rain is the main limiting factor. Site diversity can be used as one of the propagation impairment mitigation techniques. A propagation simulation tool to study a performance of Local Multipoint Distribution Systems (LMDS) has been developed to enable site-specific time-space simulations. Actual rainfall radar data were utilized as input. Simulations for various site diversity employments, network configurations, hub and terminal station locations, and under different propagation conditions (rain events) were accomplished. The results can be used for planning and optimization of specific point-to-multipoint network.

Site-Specific Space-Time Simulations of LMDS Performance Using Radar Rainfall Data

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: CD ROM Proceedings, COST 280. Brussels: COST Office, 2004.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
In this paper a concept of site-specific space-time simulations rain events are presented based on actual radar data. A database of radar data for numerous types of rain events has been established to enable system testing under different conditions. Various aspects of the system performance like site diversity can be evaluated by the simulation tool.

Space-Time Simulations of Point-to-multipoint Radio Systems Performance During Rain Events Using Radar Data

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Symposium Proceedings - URSI-F 2004. Milton: URSI, 2004. pp. 208-212. ISBN 0-646-43423-3.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole

Wide-band Parameters Prediction for Mobile Systems Channel

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of Workshop 2004. Praha: Czech Technical University in Prague, 2004. p. 338-339. ISBN 80-01-02945-X.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole

Zobecněný přístup k problematice měření v mikrovlnné technice

Autoři: prof. Ing. Miloš Mazánek, CSc., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Pavel Pechač, Ph.D., Bártík, H., prof. Ing. Karel Hoffmann, CSc., doc. Ing. Pavel Hazdra, Ph.D., Hradecký, Z.
Publikace: Měření v mikrovlnné technice. Praha: Česká elektrotechnická společnost, 2004. pp. 3-17.
Rok: 2004

Pracoviště: Katedra elektromagnetického pole
Anotace:
V příspěvku jsou zmíněny metody měření, kalibrace a experimentální výsledky v oblasti mikrovlnné techniky.

Analýza chyb při měření EMC

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: COMITE 2003 - Grantové fórum. Praha: IEEE Czechoslovakia Section, 2003. pp. 15-16. ISBN 80-86582-10-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Analýza jednotlivých druhů chyb při měření EMC v EMC komorách

Area Coverage Probability Simulation in mm Wave Band - Results and Comparison with ITU-R P.1410-2

Autoři: prof. Ing. Pavel Pechač, Ph.D., Lédl, P., Kvičera, V.
Publikace: Recommendation ITU-R P.1410-2. Brazilie: ITU, 2003. pp. 1-4.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
The comparison of area coverage results obtained by means of the ITU-R model and of simulation results for identical input values is presented.

Building Wall Attenuation Measurement

Autoři: Hradecký, Z., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2003 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2003. pp. 425-428. ISBN 80-214-2383-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Knowledge of building wall attenuation is highly demanded for an indoor propagation prediction and other applications. In the paper experimental measurement of the wall attenuation is presented. The main focus is given to discussion and demonstration of problems which accompany these types of measurements.

Comparative Evaluation of UMTS, WLAN, BWA, MBWA and UWB Systems

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2003, 12(4), 74-83. ISSN 1210-2512.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
UMTS, WLAN, BWA and UWB systems are compared in this paper. The comparative analysis covers system capacity, QoS, and radiowave propagation.

Development of Recommendations Concerning Propagation Data and Prediction Methods for Terrestrial Services from about 10 GHz to about 50 GHz

Autoři: prof. Ing. Pavel Pechač, Ph.D., Lédl, P., Kvičera, V.
Publikace: Recommendation ITU-R P.1410-2. Brazilie: ITU, 2003. pp. 5-7.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Input document related to Recommendation ITU-R P.1410-2 was provided. Questions for further testing for alternative coverage estimation procedures were described.

Education in Antennas and Radiowave Propagation for Mobile Communications

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2003 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2003. pp. I-6-I-7. ISBN 80-214-2383-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this contribution is to provide brief information on education in the field of antennas and radiowave propagation in mobile communications at the Czech Technical University in Prague, Faculty of Electrical Engineering.

Internetová forma pilotního projektu LABLINK v úloze měření směrových vlastností antén

Autoři: prof. Ing. Miloš Mazánek, CSc., Černý, P., Bártík, H., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: COMITE 2003 - Vzdělávací fórum. Praha: IEEE Czechoslovakia Section, 2003. pp. 5-17. ISBN 80-86582-11-6.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Základní metodologie přípravy a provozu vzdálené výuky pomocí distančních laboratoří a virtuálních laboratoří.

Large Dynamic Range Prediction of AOA, AOD and PDP for MIMO Systems

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Antennas & Propagation - Twelfth International Conference - ICAP 2003. London: IEE, 2003. pp. 775-779. ISBN 0-85296-752-7.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole

Measurement and Prediction of Signal Propagation for WLAN Systems

Autoři: Mikas, F., prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2003 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2003. pp. 205-208. ISBN 80-214-2383-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
This article is focused on measurement and prediction of signal propagation for WLAN (Wireless Local Area Network) systems in frequency bands 2.4 GHz and 5.2 GHz. At first WLAN standards are summarized and then two empirical models are described. Results of narrowband and wideband measurement campaign and estimated empirical parameters for coverage models are finally discussed.

Návrh metodiky měření útlumu elektromagneticky stíněných komor s rozměry do 2 metrů

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: COMITE 2003 - Grantové fórum. Praha: IEEE Czechoslovakia Section, 2003. pp. 20. ISBN 80-86582-10-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Vyvinutí metodiky pro měření malých stíněných prostor, která není doposud standardizována.

Podpora výuky předmětu šíření vln a kmitočtové plánování

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Mikas, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: COMITE 2003 - Vzdělávací fórum. Praha: IEEE Czechoslovakia Section, 2003. pp. 29-30. ISBN 80-86582-11-6.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Cílem projektu je příprava praktických a experimentálních úloh nově připravovaného předmětu magisterského strukturovaného studia Šíření vln a kmitočtové plánování. Studenti si při měření rozložení výkonové úrovně a dalších parametrů bezdrátové sítě W-LAN (na frekvenci 2,4 GHz) a současné teoretické predikci těchto hodnot budou moci sami ověřit chování elektromagnetických vln uvnitř budov. Jednotlivé úlohy budou rovněž demonstrovat součastné možnosti propojování počítačů do sítí pomocí této moderní technologie.

Results of Indoor Propagation Measurement Campaign for WLAN Systems Operating in 2.4 GHz ISM Band

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Válek, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Antennas & Propagation - Twelfth International Conference - ICAP 2003. London: IEE, 2003. p. 63-66. ISBN 0-85296-752-7.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole

Rice's K Factor and Channel Capacity Distribution Prediction for MIMO Systems

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2003 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2003. pp. 209-212. ISBN 80-214-2383-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
An indoor propagation prediction for personal communication system is demand for modern wireless services. Because of the rapidly increasing capacity of communication channel not only signal strength prediction but also wideband channel parameters mainly the impulse response and angle of arrival is needed.

Signal Fluctuations Due to the Tree Attenuation in a Millimeter Waveband

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Radioelektronika 2003 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2003. pp. 213-216. ISBN 80-214-2383-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
The radio network planning for a Local Multipoint Distribution Systems (LMDS) is often complicated by the fact that the line of sight (LOS) between the transmitter and the receiver is blocked by the vegetation of small depth (single tree). Time series tree attenuation measurement results in 38 GHz frequency band are presented in this paper. The wind speed effect on signal fluctuation was studied as well.

Šíření elektromagnetických vln

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Stanislav Zvánovec, Ph.D., Mikas, F.
Publikace: Sborník vzdělávacích a vědeckovýzkumných činností a nabídek katedry elektromagnetického pole FEL ČVUT. Praha: Československá sekce IEEE, 2003. p. 42. ISBN 80-86582-13-2.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Příspěvek pojednává o metodách výuky šíření elektromagnetických vln na katedře elektromagnetického pole ČVUT v Praze.

Site-Specific Channel Parameters Prediction for MIMO Systems

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: COMITE 2003. Praha: IEEE Czechoslovakia Section, 2003. pp. 29-30. ISBN 80-86582-09-4.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Wireless communications services are becoming ubiquitous and the main area of interest is now partly shifting from low performance wireless wide area networks to high performance local wireless networks using picocells and high data rates. In order to facilitate proper design of such networks appropriate simulation tools based on accurate signal propagation prediction are required.

Support of Tutorial by Up-to-date Methods of Electromagnetic Wave Propagation Prediction

Autoři: Klepal, M., Hradecký, Z., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of Workshop 2003. Praha: Czech Technical University in Prague, 2003. p. 496-497. ISBN 80-01-02708-2.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole

The 3D Approximation of Antenna Radiation Patterns

Autoři: Mikas, F., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Antennas & Propagation - Twelfth International Conference - ICAP 2003. London: IEE, 2003. pp. 751-754. ISBN 0-85296-752-7.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole

Time-Series Prediction of Attenuation Caused by Trees for Fixed Wireless Access Systems Operating in Millimeter Waveband

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Antennas & Propagation - Twelfth International Conference - ICAP 2003. London: IEE, 2003. pp. 646-649. ISBN 0-85296-752-7.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole

Tree Attenuation Measurement Experiment in Millimeter Waveband

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: COMITE 2003. Praha: IEEE Czechoslovakia Section, 2003. pp. 25-28. ISBN 80-86582-09-4.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Results obtained the vegetation attenuation experiment performed on 38 GHz are presented in this paper. Signal fading due to wind speed loading the tree, signal characteristics and the mean field variation in the shadowed area of the tree was investigated.

Trendy v problematice modelování šíření elektromagnetických vln pro mobilní komunikace

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radiokomunikace 2003. Pardubice: UNIT, 2003. p. 83-88.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Příspěvek přináší přehled trendů a nových požadavků v problematice modelování šíření rádiových vln se zaměřením na mobilní komunikační systémy.

Výuka antén s využitím softwaru MATHCAD

Autoři: Bártík, H., prof. Ing. Pavel Pechač, Ph.D., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: COMITE 2003 - Vzdělávací fórum. Praha: IEEE Czechoslovakia Section, 2003. pp. 2-4. ISBN 80-86582-11-6.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Ukázka koncepce výuky pomocí simulací návrhu antén programem MATHCAD

Vývoj antény pro zónová měření

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: COMITE 2003 - Grantové fórum. Praha: IEEE Czechoslovakia Section, 2003. pp. 19. ISBN 80-86582-10-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Vývoj speciální antény pro měření stínicí účinnosti

Vývoj vlnovodu pro měření útlumu stínicích materiálů

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: COMITE 2003 - Grantové fórum. Praha: IEEE Czechoslovakia Section, 2003. pp. 21. ISBN 80-86582-10-8.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
Vývoj aparatury pro rychlá provozní měření stínicí účinnosti materiálů

Wideband Measurement of Insertion Loss of Shielding Materials

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., Mikas, F., Hradecký, Z., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: COMITE 2003. Praha: IEEE Czechoslovakia Section, 2003. pp. 113-116. ISBN 80-86582-09-4.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
The aim of this paper is description of development of unique workplace capable of wideband measurement of insertion loss of shielding materials from frequencies about tens of MHz. Special attention is dedicated to construction of ferrite absorber wall and to chosen method of measurement of material insertion loss. Some of results of measurements are presented and discussed as well.

Wireless LAN Networks Design: Site Survey or Propagation Modeling?

Autoři: prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: Radioengineering. 2003, 12(4), 42-49. ISSN 1210-2512.
Rok: 2003

Pracoviště: Katedra elektromagnetického pole
Anotace:
There are two basic ways to deploy wireless LAN access points in an indoor scenario: manual deployment using a site survey based on empirical measurements or planning using a software tool with built-in signal propagation models. In this paper advantages and disadvantages of both ways are discussed. The planning based on propagation modeling is recognized as a highly preferable approach for design of large WLANs. Experimental data in this papaer were processed in MATLAB.

Application of ANT Colony Optimisation Algorithm on the Recursive Propagation Model for Urban Microcells

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: XXVIIth General Assembly the International Union of Radio Science. Maastricht: URSI, 2002. pp. 569.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Area Coverage Simulations for Millimeter Point-to-Multipoint Systems Using Statistical Model of Building Blockage

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2002, 11(4), 43-47. ISSN 1210-2512.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Dynamický model útlumu vegetace při šíření mm vln

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: WORKSHOP - Grantové fórum. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. pp. 10-11. ISBN 80-86582-06-X.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Education of Antenna Subjects with the Help of MathCad Software

Autoři: Bártík, H., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: WORKSHOP - Vzdělávací fórum - nabídka aktivit. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. p. 16-18. ISBN 80-86582-07-8.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Electromagnetic Wave Propagation Modeling Using the ANT Colony Optimization Algorithm

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2002, 11(3), 1-6. ISSN 1210-2512.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Indoor Propagation Measurement for Wireless Systems Operating in 2.45 GHz ISM Band

Autoři: Válek, M., prof. Ing. Stanislav Zvánovec, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2002, 11(4), 48-52. ISSN 1210-2512.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Model of Dynamic Effects Caused by Vegetation

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: CD ROM Proceedings, COST 280. Brussels: COST Office, 2002.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Optimalizace statistického modelu zástavby pro město Praha

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: WORKSHOP - Grantové fórum. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. pp. 13-14. ISBN 80-86582-06-X.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Prediction of Wide-Band Parameters of Mobile Propagation Channel

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D., Hradecký, Z.
Publikace: XXVIIth General Assembly the International Union of Radio Science. Maastricht: URSI, 2002. pp. 459.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Prelimary Study of Vegetation Effects on Signal Propagation in Millimeter Waveband

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Radioelektronika 2002. Bratislava: Slovak University of Technology, Faculty of Civil Engineering, 2002. pp. 255-257. ISBN 80-227-1700-2.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Scattering Measurement Experiment on 38 GHz - First Results

Autoři: Lédl, P., prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: CD ROM Proceedings, COST 280. Brussels: COST Office, 2002.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Simple Ray Tracing in Inhomogeneous Mediums Using and Colony Optimization Algorithm

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: ISAP i-02. Tokyo: The Institute of Electronics, Information and Communication Engineers, 2002. pp. 488-491.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Šíření elektromagnetických vln

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., Lédl, P., Mikas, F., prof. Ing. Stanislav Zvánovec, Ph.D.,
Publikace: WORKSHOP - Vzdělávací fórum - nabídka aktivit. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. p. 47. ISBN 80-86582-07-8.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Šíření signálu uvnitř budov pro širokopásmové bezdrátové systémy 2.5 GHz

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: WORKSHOP - Grantové fórum. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. pp. 12. ISBN 80-86582-06-X.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Vegetation Effects Modeling for Terrestrial Broadband Radio Access Systems Operating in Millimeter Waveband

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: ISAP i-02. Tokyo: The Institute of Electronics, Information and Communication Engineers, 2002. pp. 492-495.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Vegetation Effects on Signal Propagation in Millimeter Waveband

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Odborné semináře. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. pp. 33-37. ISBN 80-86582-08-6.
Rok: 2002

Pracoviště: Katedra elektromagnetického pole

Antenna Laboratory

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D., Bártík, H., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Zbyněk Škvor, CSc.,
Publikace: Proceedings of Workshop 2001. Praha: České vysoké učení technické v Praze, 2001. pp. 399. ISBN 80-01-02335-4.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Area Coverage Modeling for Systems Operating in Millimeter Wave Band

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: COMITE 2001. Praha: IEEE Czechoslovakia Section, 2001. pp. 87-90. ISBN 80-902417-9-4.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Effective Indoor Propagation Predictions

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: 54th Vehicular Technology Conference VTC Fall 2001. Piscataway: IEEE, 2001. pp. 1-4. ISSN 1090-3038. ISBN 0-7803-7007-4.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

I-PROP 1.3 - software pro plánování pikobuňkových sítí

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: Workshop CAD&CAE'2001. Praha: IEEE Czechoslovakia Section, 2001. pp. 18-19. ISBN 80-86582-04-3.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Indoor Propagation for Wireless Personal Communication Systems

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of Workshop 2001. Praha: České vysoké učení technické v Praze, 2001. pp. 400. ISBN 80-01-02335-4.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Modely pro návrh pikobuňkových sítí uvnitř budov

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Sdělovací technika. 2001, 49(4), 16-19. ISSN 0036-9942.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

New Fast Approach to Wideband Propagation Prediction in Picocells

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Antennas and Propagation (ICAP 2001). London: IEE, 2001. pp. 216-217. ISBN 0-85296-733-0.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Results of Indoor Propagation Measurement Campaign at 1900 MHz

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., Zvánovec, S.
Publikace: Radioengineering. 2001, 10(4), 2-4. ISSN 1210-2512.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Signal Propagation Aspects for Local Multipoint Distribution System (LMDS) Operating in Millimeter Wave Band

Autoři: Lédl, P., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: 10th Aachen Symposium on Signal Theory - Proceedings. Berlin: VDE Verlag, 2001. pp. 415-418. ISBN 3-8007-2610-6.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Signal Propagation for Point-to-Multipoint Systems in Millimeter Wave Band

Autoři: prof. Ing. Pavel Pechač, Ph.D., Lédl, P., prof. Ing. Miloš Mazánek, CSc.,
Publikace: COMITE 2001 - Grant Forum. Praha: Československá sekce IEEE, 2001. pp. 4-5. ISBN 80-86582-02-7.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Signal Strength and Impulse Response Prediction by Motif Model

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2001 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2001. pp. 274-277. ISBN 80-214-1861-3.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Students Projects in Modern Antennas

Autoři: prof. Ing. Pavel Pechač, Ph.D., Hradecký, Z., Klepal, M.
Publikace: Proceedings of Workshop 2001. Praha: České vysoké učení technické v Praze, 2001. pp. 401. ISBN 80-01-02335-4.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Wide-Band Indoor Propagation Prediction by Motif Model

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: 10th Aachen Symposium on Signal Theory - Proceedings. Berlin: VDE Verlag, 2001. pp. 405-408. ISBN 3-8007-2610-6.
Rok: 2001

Pracoviště: Katedra elektromagnetického pole

Anechoic and EMC Chambers - Modelling, Design, Testing

Autoři: prof. Ing. Miloš Mazánek, CSc., Klepal, M., prof. Ing. Pavel Pechač, Ph.D., doc. Ing. Milan Polívka, Ph.D., Bártík, H.
Publikace: Millenium Conference on Antennas and Propagation - AP 2000. Noordwijk: European Space Agency, 2000. pp. 156-160. ISBN 92-9092-776-3.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Bio-elektromagnetické efekty - informace z konference "MILENIUM - AP 2000"

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Biologické systémy a elektromagnetické pole. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2000. pp. 27-29. ISBN 80-01-02185-8.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Electromagnetic Field in Anechoic and EMC Chambers - Part 1 - Modelling

Autoři: prof. Ing. Miloš Mazánek, CSc., Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioengineering. 2000, 9(1), 21-26. ISSN 1210-2512.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

EMC (EMI) Standards in RF Frequency Bands

Autoři: doc. Ing. Milan Polívka, Ph.D., Klepal, M., prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of Workshop 2000. Praha: České vysoké učení technické v Praze, 2000. pp. 172. ISBN 80-01-02229-3.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

EMI Standards and Measurement above 30 MHz

Autoři: prof. Ing. Miloš Mazánek, CSc., Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2000 - Conference Proceedings. Bratislava: STU v Bratislave, FEI, 2000. pp. IV-34-IV-37. ISBN 80-227-1389-9.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Empirical Modelling of Multi-Floor Signal Propagation

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: Proceedings of Workshop 2000. Praha: České vysoké učení technické v Praze, 2000. pp. 215. ISBN 80-01-02229-3.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Empirical Models for Indoor Propagation in CTU Prague Buildings

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: Radioengineering. 2000, 9(1), 31-36. ISSN 1210-2512.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Indoor Propagation Modelling in Multi-Storey Buildings in Prague

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Millenium Conference on Antennas and Propagation - AP 2000. Noordwijk: European Space Agency, 2000. pp. 369-373. ISBN 92-9092-776-3.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Measurement Methods in Antenna Laboratory at the Department of Electromagnetic Field

Autoři: prof. Ing. Miloš Mazánek, CSc., Bártík, H., prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: Proceedings of Workshop 2000. Praha: České vysoké učení technické v Praze, 2000. pp. 184. ISBN 80-01-02229-3.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

New Indoor Propagation Model

Autoři: Klepal, M., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radioelektronika 2000 - Conference Proceedings. Bratislava: STU v Bratislave, FEI, 2000. pp. IV-54-IV-57. ISBN 80-227-1389-9.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Novel Approach to Indoor Propagation Modelling

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., Novotný, K.
Publikace: Radioengineering. 2000, 9(3), 12-16. ISSN 1210-2512.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Novel Approach to Indoor Semi-Deterministic Propagation Prediction

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., prof. Ing. Miloš Mazánek, CSc.,
Publikace: 2000 IEEE AP-S. Piscataway: IEEE, 2000. pp. 50-51. ISBN 0-7803-6372-8.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Novel Approach to Indoor Semi-deterministic Propagation Prediction

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., prof. Ing. Miloš Mazánek, CSc.,
Publikace: IEEE 2000 AP-S International Symposium and URSI National Radio Science Meeting. 2000.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

Software pro návrh bezdrátových systémů uvnitř vícepodlažních budov

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: Workshop CAD&CAE 2000. Prague: Czechoslovakia Section IEEE, 2000. pp. 1-4. ISBN 80-902417-6-3.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

System for 1900 MHz Mobile Measurements Controlled by PDA Computer

Autoři: prof. Ing. Pavel Pechač, Ph.D., Nisznanský, M., doc. Ing. Přemysl Hudec, CSc.,
Publikace: Workshop CAD&CAE 2000. Prague: Czechoslovakia Section IEEE, 2000. pp. 16-18. ISBN 80-902417-6-3.
Rok: 2000

Pracoviště: Katedra elektromagnetického pole

900 MHz Signal Propagation in Multistorey Buildings

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M.
Publikace: Proceedings of Workshop 99. Praha: České vysoké učení technické v Praze, 1999. pp. 172.
Rok: 1999

Pracoviště: Katedra elektromagnetického pole

Antény - minulost, přítomnost a možné směry jejich vývoje

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radio. 1999, 2(5-6), 9-16. ISSN 1212-0804.
Rok: 1999

Pracoviště: Katedra elektromagnetického pole

EMI Measurement in EMC Test Fascilities

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: The 10th Conference on Microwave Techniques COMITE 1999. Prague: Czechoslovakia Section IEEE, 1999. pp. 141-144. ISBN 80-902417-3-5.
Rok: 1999

Pracoviště: Katedra elektromagnetického pole

Low Profile Antennas

Autoři: prof. Ing. Miloš Mazánek, CSc., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Proceedings of Workshop 99. Praha: České vysoké učení technické v Praze, 1999. pp. 185.
Rok: 1999

Pracoviště: Katedra elektromagnetického pole

Modelling and Testing PMC Systems Inside Buildings

Autoři: prof. Ing. Pavel Pechač, Ph.D., Klepal, M., prof. Ing. Miloš Mazánek, CSc.,
Publikace: 9th International Czech-Slovak Scientific Conference Radioelektronika 99. Brno: VUT v Brně, 1999. pp. 439-441. ISBN 80-214-1327-1.
Rok: 1999

Pracoviště: Katedra elektromagnetického pole

Šíření radiových vln v atmosféře

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Radio. 1999, 2(1-2), 4-5. ISSN 1212-0804.
Rok: 1999

Pracoviště: Katedra elektromagnetického pole

900 MHz Signal Attenuation Measurement for Mobile Wireless Communications in Urban AREA

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc., doc. Ing. Přemysl Hudec, CSc., Macháček, M.
Publikace: Radioelektronika 98. Brno: VUT v Brně, 1998. pp. 285-288. ISBN 80-214-0983-5.
Rok: 1998

Pracoviště: Katedra elektromagnetického pole

Anechoic Chambers Testing

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: 43. Internationales Wissenschaftliches Kolloquium. Ilmenau: TU Ilmenau, 1998. pp. 307-310. ISSN 0943-7207.
Rok: 1998

Pracoviště: Katedra elektromagnetického pole

Design and Testing of Anechoic Chambers for Antenna Measurement

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Zbyněk Škvor, CSc.,
Publikace: Workshop 98. Praha: České vysoké učení technické v Praze, 1998. pp. 271-272.
Rok: 1998

Pracoviště: Katedra elektromagnetického pole

Mobilní a personální radiokomunikace na katedře elektromagnetického pole

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Transfer 98. Praha: České vysoké učení technické v Praze, 1998. pp. 175-176.
Rok: 1998

Pracoviště: Katedra elektromagnetického pole

The Far-field Antenna Measurement System Upgrade

Autoři: prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Workshop 98. Praha: České vysoké učení technické v Praze, 1998. pp. 267-268.
Rok: 1998

Pracoviště: Katedra elektromagnetického pole
Anotace:
Modernizace anténního měřicího systému.

Cavity Backed Patch Antenna with Shorted Nonradiating Edges

Autoři: prof. Ing. Miloš Mazánek, CSc., Závěšický, P., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Workshop 97. Praha: České vysoké učení technické v Praze, 1997. pp. 913-914.
Rok: 1997

Pracoviště: Katedra elektromagnetického pole
Anotace:
Mikropásková anténa s dutinou se zkratovanými nevyzařujícími hranami

Cavity-Backed Path Antennas

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D., doc. Ing. Milan Polívka, Ph.D.,
Publikace: ICAP 97. London: Institution of Electrical Engineers, 1997. pp. 126-129. ISBN 0-85296-686-5.
Rok: 1997

DOI: 10.1049/cp:19970223
Odkaz: https://doi.org/10.1049/cp:19970223
Pracoviště: Katedra elektromagnetického pole
Anotace:
Several configurations of cavity-backed patch antennas are described and compared. Theoretical studies were accompanied with both impedance matching and radiation pattern measurements. The main goal of the project is to achieve smaller dimensions with a sufficient frequency bandwidth of microstrip low profile antennas. Two construction approaches-broadband cavity backed, shorted nonradiating edge, and slot & notch cut microstrip antenna-were combined

CNProp 2.0 - CAD Software for Frequency Planning in Cellular Communication Systems

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Workshop CAD and CAE 97. Praha: ČVUT FEL, Katedra elektromagnetického pole, 1997. pp. 4-6. ISBN 80-902417-1-9.
Rok: 1997

Pracoviště: Katedra elektromagnetického pole

Combined Microstrip Antenna Arrangements

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Zbyněk Škvor, CSc.,
Publikace: Radioelektronika '97. Bratislava: STU v Bratislave, 1997. pp. 264-267. ISBN 80-227-0943-3.
Rok: 1997

Pracoviště: Katedra elektromagnetického pole

Patch Antennas with Reduced Dimensions

Autoři: prof. Ing. Miloš Mazánek, CSc., doc. Ing. Milan Polívka, Ph.D., prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Zbyněk Škvor, CSc.,
Publikace: COMITE 1997. Pardubice: Univerzita Pardubice, 1997. pp. 112-115. ISBN 80-902417-0-0.
Rok: 1997

Pracoviště: Katedra elektromagnetického pole

Planning Tool for Channel Alignment in Cellular Networks

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Workshop 97. Praha: České vysoké učení technické v Praze, 1997. pp. 973-974.
Rok: 1997

Pracoviště: Katedra elektromagnetického pole
Anotace:
Návrh frekvenčního plánu v buňkových sítích

Automatizovaný systém pro měření směrových charakteristik antén

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc., doc. Ing. Přemysl Hudec, CSc., doc. Ing. Milan Polívka, Ph.D.,
Publikace: Workshop CAD&CAE 96. Praha: ČVUT FEL, Katedra elektromagnetického pole, 1996. pp. 47-48.
Rok: 1996

Pracoviště: Katedra elektromagnetického pole

Experimental Demonstration of the Ray Tracing Method

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Radioelektronika '96. Brno: VUT v Brně, 1996. pp. 451-454. ISBN 80-214-0617-8.
Rok: 1996

Pracoviště: Katedra elektromagnetického pole

Propagation Study for Microwave Radio Systems, XPD, Interferences, Absorptions

Autoři: prof. Ing. Miloš Mazánek, CSc., prof. Ing. Pavel Pechač, Ph.D., Hajný, M., Janík, J., Kvičera, V., Kolář, J., Kerhart, J., Čejka, P.
Publikace: 26 European Microwave Conference. Kent: Nexus House, 1996. pp. 925-926. ISBN 1-899919-08-2.
Rok: 1996

Pracoviště: Katedra elektromagnetického pole

Software for Cellular Network Propagation Studies - SNProp

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Workshop CAD&CAE 96. Praha: ČVUT FEL, Katedra elektromagnetického pole, 1996. pp. 10-12.
Rok: 1996

Pracoviště: Katedra elektromagnetického pole

The Material Dielectric Characteristic Measurement

Autoři: prof. Ing. Miloš Mazánek, CSc., Brychta, Z., prof. Ing. Karel Hoffmann, CSc., Novotný, K., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Workshop 96. Praha: České vysoké učení technické v Praze, 1996. pp. 767-768.
Rok: 1996

Pracoviště: Katedra elektromagnetického pole

The Propagation of Electromagnetic Waves for CMR and PCS

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Workshop 96. Praha: České vysoké učení technické v Praze, 1996. pp. 759-760.
Rok: 1996

Pracoviště: Katedra elektromagnetického pole

Distribuce signálu pro mobilní komunikace

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc., doc. Ing. Přemysl Hudec, CSc., Hajný, M.
Publikace: Workshop CAD&CAE 1995. Praha: ČVUT FEL, Katedra elektromagnetického pole, 1995. pp. 1-3.
Rok: 1995

Pracoviště: Katedra elektromagnetického pole

MM Wave Propagation Experiment

Autoři: prof. Ing. Miloš Mazánek, CSc., Zlámal, P., Bártík, H., Janík, J., prof. Ing. Pavel Pechač, Ph.D.,
Publikace: Workshop 95. Praha: České vysoké učení technické v Praze, 1995. pp. 599-600.
Rok: 1995

Pracoviště: Katedra elektromagnetického pole

Návrh VF radioreléových tras do 100GMz

Autoři: prof. Ing. Pavel Pechač, Ph.D., doc. Ing. Přemysl Hudec, CSc., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Workshop CAD&CAE 1995. Praha: ČVUT FEL, Katedra elektromagnetického pole, 1995. pp. 21-24.
Rok: 1995

Pracoviště: Katedra elektromagnetického pole

Propagation Prediction in Microcells for UMF Personal Communication Systems

Autoři: prof. Ing. Pavel Pechač, Ph.D., prof. Ing. Miloš Mazánek, CSc.,
Publikace: 40. Internationales Wissenschaftliches Kolloquium. Ilmenau: TU Ilmenau, 1995. pp. 78-80. ISSN 0943-7207.
Rok: 1995

Pracoviště: Katedra elektromagnetického pole

The 37 GHz Short Distance Experiment

Autoři: prof. Ing. Miloš Mazánek, CSc., Bártík, H., Janík, J., prof. Ing. Pavel Pechač, Ph.D., Zlámal, P.
Publikace: MITEKO 95. Pardubice: Univerzita Pardubice, 1995. pp. 11-14.
Rok: 1995

Pracoviště: Katedra elektromagnetického pole

The Antenna Characteristics Measurement System

Autoři: prof. Ing. Pavel Pechač, Ph.D., doc. Ing. Přemysl Hudec, CSc., Zlámal, P., prof. Ing. Miloš Mazánek, CSc.,
Publikace: Workshop 95. Praha: České vysoké učení technické v Praze, 1995. pp. 587-588.
Rok: 1995

Pracoviště: Katedra elektromagnetického pole

Propagation measurement for mobile Satcom and Satnav systems using a small remote-controlled airship

Autoři: prof. Ing. Pavel Pechač, Ph.D., Holiš, J., Ing. Tomáš Kořínek, Ph.D., Kvičera, M., Horák, P.
Publikace: neuvedeno.

Pracoviště: Katedra elektromagnetického pole

prof. Ing. Pavel Pechač, Ph.D.

Všechny publikace

Commercial Microwave Links for Urban Rainfall-runoff Modelling

Narrowband validation of a deterministic model in UAV scenarios

On Distance Factor in Rain Attenuation Predictions

TEL4RAIN: MĚŘENÍ SRÁŽEK S VYSOKÝM ROZLIŠENÍM POMOCÍ TELEKOMUNIKAČNÍCH MIKROVLNNÝCH SPOJŮ

Analysis of Propagation of Electromagnetic Waves in Atmospheric Hydrometeors on Low-Elevation Paths

Comparison of Measured and Theoretically Predicted Rain Attenuation at 32 GHz and 38 GHz

Estimating wet antenna effect from long-term attenuation statistics of short commercial microwave links

State Propagation Channel Model for 2 GHz UAV Links in Cluttered Environment

A New Model for Scattering From Tree Canopies Based on Physical Optics and Multiple Scattering Theory

A New Propagation Channel Synthesizer for UAVs in the Presence of Tree Canopies

Analysis of One-year Data of Slant Path Rain Attenuation at 19 and 39 GHz in Prague

On Horizontal Distribution of Vertical Gradient of Atmospheric Refractivity

Open area 2 x 2 MIMO channel model for 2 GHz low-elevation links with diversity and capacity applications

Water Vapor Density Profile Statistics in the Atmospheric Boundary Layer

A Model for the Detailed Analysis of Radio Links Involving Tree Canopies

Attenuation due to hydrometeors in three millimeter wave bands

Clutter Loss Modelling for Low Elevation Link Scenarios

Inverse Gaussian-based composite channel model and time series generator for land mobile satellite systems under tree shadowing

Modeling scattering from tree canopies for UAV scenarios

Sensitivity Analysis of Multiple Scattering Theory Applied to Tree Canopies at Microwave Frequencies

A Mode-Matching Technique for Analysis of Scattering by Periodic Comb Surfaces

Experimental Study on Terrestrial Links Enhancement at 11 and 38 GHz

First-Order Statistics Prediction for a Propagation Channel of Arbitrary Non-Geostationary Satellite Orbits

Generalized Propagation Channel Model for 2GHz Low Elevation Links Using a Ray-tracing Method

Inclusion of Higher Order Diffracted Fields in the Epstein-Peterson Method

Influence of Input Terrain Profile Resolution on Diffraction Modeling

Initial Results from a Measurement Campaign for Low Elevation Angle Links in Different Environments

Measurements of Horizontal Variations of Radio Refractivity - First Results

Scattering from Single Isolated Tree Based on Physical Optics: Preliminary Model

Seasonal Variations of Polarization Diversity Gain in a Vegetated Area considering High Elevation Angles and a Nomadic User

Spatial Correlation of Vertical Gradient of Refractivity on Large Scales

Advanced Modelling of Intelligent Walls for Indoor Smart Environments

First Results of Concurrent Rain Attenuation Measurement in Three Millimeter Wave Bands

Frequency Selective Building Facades

Modeling of First-Order Statistics of LMS Channel under Tree Shadowing for Various Elevation Angles at L-Band

Modeling of First-Order Statistics of the MIMO Dual Polarized Channel at 2 GHz for Land Mobile Satellite Systems under Tree Shadowing

Novel Mobility Model for Indoor Conference Scenarios

Short-Term Terrain Diffraction Measurements From L- to Q-Band: Results and Analysis

World Maps of Atmospheric Refractivity Statistics

Atmospheric Refractivity Profiles and Microwave Propagation on a Terrestrial Path - Experiment and Simulation

Closed-Form Approximation for Parallel-Plate Waveguide Coefficients

Controlling Coverage for Indoor Wireless Networks Using Metalized Active FSS Walls

EM Wave Transmission through a Window Blind Structure

Estimation of the Radio Refractivity Gradient From Diffraction Loss Measurements

Feasibility of UAV Link Space Diversity in Wooded Areas

Measurement of Window Blind Attenuation at 5-50 GHz

Short-Term Terrain Diffraction Measurements: Preliminary Results

Space Diversity Analysis for Low Elevation Links in a Wooded Area

Space Diversity Gain in Urban Area Low Elevation Links for Surveillance Applications

The UAV Low Elevation Propagation Channel in Urban Areas: Statistical Analysis and Time-Series Generator

Broadband Spectrum Survey Measurements for Cognitive Radio Applications

Building Penetration Loss Modelling for Satellite Services At L-, S- and C-band

Controlling Coverage Using New Concept of Pre-Installed Infrastructure

Controlling Propagation Environments Using Intelligent Walls

Estimation of Radio Refractivity Profile Gradient From Multiple LOS Links Using Artificial Neural Networks - First Results

Excess Loss for High Elevation Angle Links Shadowed by a Single Tree: Measurements and Modeling

First and Second Order Statistics of Clear-Air Attenuation on 11 GHz Terrestrial Path

First Results of Rain Spatial Parameters Analyses for Optical Links

Frequency Dependence of Vegetation Shadowing Loss for Satellite Services

Impulse Radio UWB Pulse Shaping for Cognitive Radio Applications

Influence of Antenna Characteristics on Elevation Dependence of Building Penetration Loss for High Elevation Links

Intelligent Walls as Autonomous Parts of Smart Indoor Environments

Long-term Measurements of Refractive Index Structure Constant in Atmospheric Boundary Layer

On the Short-term Time Evolution of Elevated Ducting Layers

Parameters of Vertical Profiles of Temperature, Humidity and Refractive Index of Air in the Lowes Troposphere

Propagation Measurements in a Wide Range of Elevation Angles Using a Remote-Controlled Airship

Space Diversity Analysis for Low Elevation Links in Urban Areas

Advanced 3D Indoor Propagation Model: Calibration and Implementation

Attenuation Due to Vegetation for Satellite Services: Winter Season Measurement

Building Penetration Loss for Satellite Services at L-,S- and C band: Measurement and Modeling

Elevation Dependence of Building Penetration Loss for Satellite Services at 3.5 GHz and 5.0 GHz

Estimation of the Refractivity Structure of the Lower Troposphere From Measurements on a Terrestrial Multiple-Receiver Radio Link

Excess Loss Model for Low Elevation Links in Urban Areas for UAVs

Influence of Modelling Diffraction on Electromagnetic Wave Propagation Predictions in Subterranean Galleries

Influence of Receiver Position on Building Penetration Loss at 5.0 GHz for High Elevation Angles

Initial Results of Foliage Attenuation Measurements of a Tree-lined Passage at L, S and C Bands for High Elevation Angle Links

Intelligent Controlling of Wireless Cognitive Networks in Indoor Scenarios Using Intelligent Walls

Measured and Simulated Fluctuations of Received Power on 11 GHz Terrestrial Path Using Vertical Profiles of Atmospheric Refractivity