Menu
EN

Vyhledávání

Lidé

prof. Ing. Karel Hoffmann, CSc.

Všechny publikace

Novel Waveguide Sensors for Contactless Ultrashort-Distance Measurements

  • Autoři: Baskakova, A., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: IEEE Transactions on Microwave Theory and Techniques. 2022, 70(1), 565-575. ISSN 0018-9480.
  • Rok: 2022
  • DOI: 10.1109/TMTT.2021.3107503
  • Odkaz: https://doi.org/10.1109/TMTT.2021.3107503
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Novel sensors for ultra-short-distance measurements, with choke flanges applied at the open ends of both a WR10 waveguide and a circular waveguide, featuring a radius of 1.42 mm, are proposed. Field distributions between the sensors and a target are analyzed and explained on the basis of higher order modes of a radial line formed by the sensors and a planar reflective target. A robust equivalent circuit using a cascade of lossy waveguides is proposed and a new calibration/correction method is derived. Properties of both sensors are verified experimentally for target distances of 0 to 6 mm (~1½ of wavelength). The new circular waveguide sensor operates in a frequency band of 75-76 GHz with a maximum error of measured distance 19 m. The new rectangular waveguide sensor enables to use an outstanding applicable frequency bandwidth from 76 up to 86 GHz, with best properties around 80 GHz, where the maximum error of the measured distance is 12 m. The new sensors make possible to achieve about ten times smaller distance measurement errors in comparison with the state of the art sensors.

W-Band Imaging Sensor Using a Rectangular Waveguide Structure With Choke

  • Autoři: Baskakova, A., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: IEEE Microwave and Wireless Components Letters. 2022, 32(3), 230-233. ISSN 1531-1309.
  • Rok: 2022
  • DOI: 10.1109/LMWC.2021.3134472
  • Odkaz: https://doi.org/10.1109/LMWC.2021.3134472
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new application of a rectangular waveguide structure with a choke from Baskakova and Hoffmann (2021) is proposed for high-contrast imaging in the W-band. As with homogeneous lossy waveguides, the field distribution in front of the open-ended sensor is observed and a calibration/correction method is applied. The sensor is evaluated using planar metal- dielectric samples under test (SUT), thus enabling the detection of different materials with a standoff distance ranging from 0.08 to 1.07 λ₀. The sensor can determine both amplitudes and the contrast of the reflection coefficients correctly at the reference plane of the SUT, which is not possible for state-of-the-art sensors. The maximum contrast of the imaging is greater than 26 dB. A spatial resolution and minimum resolution for the tracking of SUT local properties of 1.9 mm are achieved at standoff distances of 2 and 1 mm, respectively.

Broadband Target Simulator for FMCW Radar Sensors With Mirror Target Suppression

  • DOI: 10.1109/COMITE52242.2021.9419874
  • Odkaz: https://doi.org/10.1109/COMITE52242.2021.9419874
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This article describes a target simulator for FMCW radar sensors which, working on the frequency shift principle, deals with the presence of an unwanted (mirror) target. A simple method is proposed to suppress the mirror target by utilizing an IQ mixer in simulator circuitry which enables single-sideband modulation. Achievable combinations of speed and distance of simulated targets are also presented. In addition, the generation of targets closer than the physical distance of the simulator, a radar parameter estimation and a simulator calibration are included. All presented principles were verified by a laboratory experiment with a 24 GHz FMCW radar module and other commercially available components.

Design of a Scalar Free-Space Measurement System

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This article offers insight into the design andrealization of a scalar free-space measurement system applicableto inverse synthetic aperture imaging purposes. The basics of themeasurement method are reminded and a calibration procedureof the main hardware (HW) imperfection is proposed. Themajority of the article is devoted to correctly choosing the HWcomponents, modulation scheme, assembly of the system and itscharacterisation. The functionality of the system was carried outvia the imaging of a metallic plate.

Design of Microstrip Dual-Mode Impedance Transformers

  • Autoři: Baskakova, A., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: IEEE Microwave and Wireless Components Letters. 2019, 29(2), 86-88. ISSN 1531-1309.
  • Rok: 2019
  • DOI: 10.1109/LMWC.2018.2887313
  • Odkaz: https://doi.org/10.1109/LMWC.2018.2887313
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    new four-port component, dual-mode impedance transformer for wideband matching of two microstrip lines with equal characteristic impedance and a coupled microstrip line with general even- and odd-mode impedances, is proposed. Practical realization problems are discussed and a new dimension correction approach is derived. Two transformers between 50-Ω microstrips and microstrip coupled lines with even/odd impedances 100 Ω /68 Ω and 36 Ω /27 Ω , respectively, were built. The concept was experimentally verified at the frequency band 0.01-16 GHz.

Investigation of Waveguide Sensors for Ultra-Short-Distance Measurements

  • Autoři: Baskakova, A., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 2019 93rd ARFTG Microwave Measurement Conference (ARFTG). Boston: IEEE, 2019. ISBN 978-1-7281-0506-2.
  • Rok: 2019
  • DOI: 10.1109/ARFTG.2019.8739174
  • Odkaz: https://doi.org/10.1109/ARFTG.2019.8739174
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Experimental study of two R100 open waveguides with a plain and a choke flanges at the ends newly applied as sensors for ultra-short distance measurements is presented. Properties of the sensors were mapped by measuring their reflection coefficients in the frequency band from 8 GHz to 12.4 GHz for distances of a reflective target from 0 mm up to 20 mm. Quasi-linear dependence of the phase of the measured reflection coefficient on the distance to the target was discovered at certain frequencies for both sensors. The sensors enable to measure the distances from zero to more than a half of the wavelength.

Scalar Method for Reading of Chipless RFID Tags Based on Limited Ground Plane Backed Dipole Resonator Array

  • DOI: 10.1109/TMTT.2019.2918287
  • Odkaz: https://doi.org/10.1109/TMTT.2019.2918287
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    In this paper, we propose a novel frequency domain reading method for the chipless RFID tags. It is based on a single scalar measurement of transmission coefficient magnitude between two antennas by the presence of a tag. The method enables to reliably read the chipless RFID tags based on a dipole resonator array, which is backed by a limited ground plane, in a real environment outside the anechoic chamber. Moreover, it suits simple, yet not necessarily well impedance matched, reader antennas represented by an open end of the rectangular waveguide. The method was verified experimentally in the frequency band of 7–11 GHz.

Simple sensors for ultra-short distance measurements

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Baskakova, A.
  • Publikace: Proceedings of European Microwave Conference in Central Europe (EuMCE 2019). Louvain-la-Neuve: European Microwave Association (EuMA), 2019. p. 158-162. ISBN 978-2-87487-066-8.
  • Rok: 2019
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Experimental study of two R100 waveguide opens with a flange and with no flange newly applied as sensors for short distance measurements is presented. Properties of the sensors were mapped measuring their reflection coefficient in the frequency band 8 GHz to 12.4 GHz for distances of a reflective target from 0 mm up to 20 mm. Quasi-linear dependence of the phase of the measured reflection coefficient on the distance between the sensor and the target was discovered at certain frequencies for distances from 0 mm up to 14.5 mm.

An Interferometric Sensor for Scanning Microwave Microscopy Application

  • Autoři: Baskakova, A., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 2018 Asia-Pacific Microwave Conference Proceedings. Tokio: The Institute of Electronics Information and Communication Engineers of Japan, 2018. p. 1232-1234. ISBN 978-1-5386-2184-4.
  • Rok: 2018
  • DOI: 10.23919/APMC.2018.8617173
  • Odkaz: https://doi.org/10.23919/APMC.2018.8617173
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The development of an interferometric sensor for scanning microwave microscopy is proposed. The structure is based on the concept of Wilkinson power divider; by using multistage sections of microstrip lines and resistors the operational bandwidth is increased. The optimization of dimension parameters and resistors values is discussed. The sensor was experimentally investigated in frequency band 45 MHz to 26 GHz. 40 times reduction of the reflection coefficient measurement uncertainty compared to standard VNA reflection measurement was achieved.

A New Interferometric Sensor for Scanning Near-Field Microwave Microscopy

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Baskakova, A.
  • Publikace: Proceedings of 89th ARFTG Microwave Measurement Conference. Piscataway (New Jersey): IEEE, 2017. ISBN 978-1-5386-2747-1.
  • Rok: 2017
  • DOI: 10.1109/ARFTG.2017.8000829
  • Odkaz: https://doi.org/10.1109/ARFTG.2017.8000829
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new microstrip sensor using the transmission interferometric measurement principle for scanning near-field microwave microscopy is presented. The structure originates from a Wilkinson power divider but has a resistor removed. The wideband design was verified by simulation using AWR Microwave Office and experimentally in frequency band of 45 MHz to 20 GHz. Ten times suppression of measurement uncertainties due to noise of a vector network analyzer was achieved. The structure is simple, cheap and mechanically stable with no moveable part.

Advanced Evaluation of Minimum Insertion Loss of Power-Line EMI/RFI Filters in RF and Microwave Frequency Bands

  • DOI: 10.1109/TEMC.2017.2689926
  • Odkaz: https://doi.org/10.1109/TEMC.2017.2689926
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This article concerns a new approach for the characterization of power-line EMI/RFI filters in a general impedance environment and continues to broaden the scope of one of previously published works. Specifically, the paper focuses on analyzing the lowest possible insertion loss of threewire, single-phase EMI/RFI power-line filters in their stop-band at high megahertz or gigahertz frequencies.

General Method for Characterization of Power-Line EMI/RFI Filters Based on S-Parameter Evaluation

  • DOI: 10.1109/TEMC.2016.2583221
  • Odkaz: https://doi.org/10.1109/TEMC.2016.2583221
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This paper deals with a general working approach for determining the lowest possible insertion loss of power-line interference filters in their stop bands at high megahertz or gigahertz frequencies. It is shown that at these frequencies, the measurement methods recommended for testing of interference filters in available standards for frequencies up to 1 GHz fail in determining their lowest possible insertion loss. This problem is solved by the newly developed method which also enables the characterization of concerned filters in a completely impedance unknown environment. It is based on two-port vector network analyzer measurement and postmeasurement data processing applying an impedance matching technique. Experimental verification of the new method using two Maury Microwave automated tuners and a cascade of low-pass coaxial filters was performed in the frequency band from 6 to 12 GHz. The results show that measurement-evaluation procedures performed according to the newly developed method provide more reliable and precise results when compared to measurement procedures corresponding to methods described in common standards. The new method was also applied to the characterization of a professional EMI/RFI filter from 1 to 10 GHz.

Traceable High Impedance Calibration Standards

  • Autoři: Haase, M., prof. Ing. Karel Hoffmann, CSc., Hudlička, M.
  • Publikace: 87th ARFTG Microwave Measurement Conference. Piscataway: IEEE, 2016. pp. 16-19. ISBN 978-1-5090-1308-1.
  • Rok: 2016
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper deals with S-parameters characterization process of newly developed and fabricated high impedance calibration standards, based on APC-7 microwave connectors, suitable for extreme impedances measurement. It evaluates all critical factors playing significant role in the process including dimension and material characterization and used fabrication technology. A combination of the electromagnetic simulator ANSYS HFSS and precise traceable microwave measurements is used for their final characterization and evaluation of the uncertainty. Finally, some technological solutions which could further improve the characterization uncertainty are proposed.

Vliv vyzařování adaptéru koaxiál - mikropásek při přesném vektorovém měření

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Referáty přednesené na 44. semináři Pravidelné setkání zájemců o mikrovlnnou techniku. Praha: Česká elektrotechnická společnost, 2016. ISBN 978-80-02-02654-9.
  • Rok: 2016
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Jsou analyzovány problémy spojené s vyzařováním adaptérů koaxiál-mikropásek při přesném vektorovém měření. Je ukázána a kvantifikována fyzikální podstata problému. Je navrženo konstrukční řešení potlačující vyzařování. Toto řešení je testováno pomocí 3D simulací elektromagnetického pole i experimentálně.

Calibration/Verification Standards for Measurement of Extremely High Impedances

  • Autoři: Haase, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of 86th ARFTG Symposium: Microwave Measurements with Applications to Bioengineering and Biomedicine. Piscataway: IEEE, 2015. pp. 83-86. ISBN 978-1-4673-9246-4.
  • Rok: 2015
  • DOI: 10.1109/ARFTG.2015.7381474
  • Odkaz: https://doi.org/10.1109/ARFTG.2015.7381474
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper concerns the design of calibration/verification standards suitable for a system developed to be capable of measuring extreme impedances. Values of standard impedances cover the range from 5 kΩ to approx. 200 kΩ. The paper focuses on selecting a structure compatible with an APC-7 connector and its optimization taking into account also the presence of higher order modes and technology demands. CST Microwave Studio (CST) is used for simulations. S-parameters of the final structure are verified by means of an independent 3D simulator ANSYS HFSS (HFSS).

High Resolution Range Imaging Via Model-based Compressed Sensing

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper proposes a method for high resolution range imaging at millimeter wave frequencies (85 GHz to 100 GHz) based on model-based compressed sensing (CS). A detailed description of the underlying CS-theory, the experimental setup and radar sensor are presented along with experimental results for one-dimensional range imaging. The proposed method is based on motorized reference measurements, which form the dictionary matrix for subsequent CS-processing. These reference measurements are tested against measurements from a glass fiber reinforced polymer (GFRP) component. A comparison of the CS-processed data to a classical Fourier-domain analysis revealed superior ranging performance of the CS-approach at the expense of a higher signal processing load.

Microstrip Open - Problematic Calibration Standard

  • DOI: 10.1109/ARFTG.2015.7162921
  • Odkaz: https://doi.org/10.1109/ARFTG.2015.7162921
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Microstrip open end (Open) applied as a calibration standard in frequency band up to 26 GHz was analyzed using CST Microwave Studio (CST). Arlon CuClad 233 with thickness 0.508mm was used for simulations. Different lengths of the microstrip lines in front of the Open were considered. Significant influence of the radiated field and the length of the microstrip line on the reflection coefficient magnitude of the standard in the order 0.01 was discovered. Physical explanation of the phenomenon is given .

Six-Port Spatial Electromagnetic Wave Measurement

  • DOI: 10.1109/TMTT.2014.2365024
  • Odkaz: https://doi.org/10.1109/TMTT.2014.2365024
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new method for measuring free-space electromagnetic waves, based ona scalar interferometric measurement principle similar to the six-port concept, is presented. A proof of concept was performed at frequency band 6-12 GHz. The corresponding measurement system contains both a reference channelfeaturing a transmitting antenna directly irradiating receiving antenna, and,a test channel which has a transmitting antenna irradiating a test object. A wave reflected or scattered by the test object, and the reference wave phaseshifted in several steps, both coherent, interfere in the receiving antenna. Redundancy is exploited via a multistate regime of measurement which enablesto reduce uncertainty of measurement. A geometrical representation of theapproach in the complex plane makes it possible to estimate measurement uncertainties. Precise computing of uncertainties based on the Monte Carlo Method is alsoperformed.

Study of calibration standards for extreme impedances measurement

  • Autoři: Haase, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 83rd ARFTG microwave measurement conference. Piscataway: IEEE, 2014. pp. 38-43. ISBN 978-1-4799-4425-5.
  • Rok: 2014
  • DOI: 10.1109/ARFTG.2014.6899512
  • Odkaz: https://doi.org/10.1109/ARFTG.2014.6899512
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper describes first results of pioneering research in the field of calibration standards for the measurement of extreme impedances. It is a necessary step for the measurement of extreme impedances since the method has been developed. The proposed calibration standards are based on coaxial microwave connector APC-7 and were extensively analyzed in CST Microwave Studio at the frequency range from 0.1 GHz to 18 GHz. Some of the analyzed structures seem to be promising for measurements of tiny very high impedance structures like carbon nanotubes or atto-farad varactors.

Microwave interferometric method for metal sheet thickness measurement

  • DOI: 10.1109/ARFTG.2013.6579036
  • Odkaz: https://doi.org/10.1109/ARFTG.2013.6579036
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new microwave method capable of contactless thickness measurement of metal sheets with high resolution has been proposed. First experimental results in X-band are reported. The method is based on precise interferometric phase evaluation of a signal reflected step by step from two surfaces of a metal sheet whose thickness is to be measured. This is achieved using interference between the reflected and reference signals. Micrometer resolution at 10 GHz can be expected.

Novel Multimode Planar Absorbing Structure

  • Autoři: Příhoda, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: IEEE Microwave and Wireless Components Letters. 2013, 23(1), 7-9. ISSN 1531-1309.
  • Rok: 2013
  • DOI: 10.1109/LMWC.2012.2234093
  • Odkaz: https://doi.org/10.1109/LMWC.2012.2234093
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A block of absorbing material covered by a conductive plate and placed on a microstrip line forms a structure which makes possible multimode propagation. The detailed modal analysis of the structure is presented. Based on the analysis a new planar multi-interference structure which utilizes interferences between excited modes is presented. The mentioned structure have extended bandwidth of attenuation. Experimental results and 3D electromagnetic simulations up to 18 GHz are presented.

Precise Measurement Using Coaxial-to-Microstrip Transition Through Radiation Suppression

  • DOI: 10.1109/TMTT.2013.2272380
  • Odkaz: https://doi.org/10.1109/TMTT.2013.2272380
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This paper presents a study about the radiation problem of coaxial-to-microstrip launchers and suggests their improvement with a novel design. The proposed solution is based on a coaxial-to-microstrip transition enclosed in a parallel-plate transmission line that has its cutoff frequency above the working frequency band of interest. Any radiated field is quickly attenuated because it is propagating inside a subcritical parallel-plate transmission line. The proposed method is extensively analyzed in the CST Microwave Studio and simulation results are verified on fabricated test-fixture by multiple measurements. The proposed solution improves the accuracy and reduces the uncertainty during measurements on microstrip.

Self-calibrating evaluation method for microwave interferometry measurements

  • DOI: 10.1049/el.2012.3122
  • Odkaz: https://doi.org/10.1049/el.2012.3122
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Microwave interferometry provides a sensitive measurement of amplitudes and phases of reflections. Thanks to the interferometric system can be used used to measure non-electric quantity such as distance. This letter presents a new method to evaluate data from microwave interferometer. The method is compared with the previously used procedure. The new method provides more accurate results and also offers the possibility of self-calibration.

Spatial Vector Measurement Based on Six-Port Concept

  • DOI: 10.1109/ARFTG.2013.6579045
  • Odkaz: https://doi.org/10.1109/ARFTG.2013.6579045
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new vector measurement method of electromagnetic field distribution in space based on a scalar measurement similar to the six-port concept is presented. In addition to transmitting and receiving, the antenna system utilizes a reference antenna continuously irradiating the receiving antennas via a coherent signal with several phase shifts. The functionality of the method was verified experimentally using three antennas in the 8 – 12 GHz frequency band. The method is applicable to imaging systems or for measuring the near field of antennas, etc.

Transistor Oscillator 24.7 GHz Stabilized by HEM221 Mode of Rectangular Dielectric Resonator

  • Autoři: Haase, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of 13th Conference on Microwave Techniques COMITE 2013. Pardubice: Univerzita Pardubice, 2013. pp. 62-64. ISBN 978-1-4673-5513-1.
  • Rok: 2013
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A transistor oscillator 24.7 GHz with rectangular dielectric resonator (DR) working in HEM221 mode in feedback path between drain and gate was developed in the microstrip structure. Lower mode oscillations were suppressed by properly designed layout of the circuit. 4.5 dBm output power and 100 dBc/Hz phase noise at 100 kHz from the carrier was achieved with transistor VMMK-1225.

A Procedure for Measurement of S-parameters and Eye-diagram of Backplane Using Two-port VNA

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Randus, M.
  • Publikace: 80th ARFTG Microwave Measurement Conference Proceedings. Piscataway: IEEE, 2012. p. 80-82. ISBN 978-1-4673-4820-1.
  • Rok: 2012
  • DOI: 10.1109/ARFTG.2012.6422421
  • Odkaz: https://doi.org/10.1109/ARFTG.2012.6422421
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A procedure for measurement of eye-diagram of a backplane based on single-ended two port s-parameters was designed and experimentally verified. Eye-diagram was derived using impulse response corresponding to calculated differential s-parameters of backplane pair lines. FCI AirMax VS connectors were used to connect the backplane. The procedure was verified in frequency band up to 5 GHz and transmission rate 1.25 Gbits/s.

A Procedure for Measurement of S-parameters and Eye-diagram of Backplane Using Two-port VNA

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Randus, M.
  • Publikace: 80th ARFTG Microwave Measurement Conference Proceedings. Piscataway: IEEE, 2012. ISBN 978-1-4673-4820-1.
  • Rok: 2012

Measurement and Simulation of Coaxial to Microstrip Tansitions' Radiation Properties and Sbstrate Influence

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A radiation and electro-magnetic (EM) field analysis of coaxial-to-microstrip transitions is presented. Radiation is quantified by simulation and measurement of a crosstalk between two Omni-Spectra's transitions using microstrip 'open' calibration standards at different positions. Simulation results are compared to the measured data and good agreement is reported on two different substrates. The evaluation method which is used to analyze quality of the transition and its radiation properties was already developed and verified on a grounded coplanar waveguide (CPWG) transmission line. Results can be used to estimate uncertainty budget of the calibrated measurement with respect to the measured radiation. Results on different substrates show interesting behaviour and can prove useful when choosing suitable substrate for specific test-fixture.

Precise microwave measurement of liquid level

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A simple interferometric waveguide setup has been developed, enabling for precise distance measurement of liquid level. Total reflection from the liquid surface is not necessary. For the most common case of lossy liquids, reflection phase must be determined properly. This may be accomplished by the use of a waveguide short for calibration. The setup was tested in measurement of water level. Resolution of the order of micrometers was achieved in X-band.

Radiation properties of Coaxial-to-coplanar transitions in K band

  • DOI: 10.1049/el.2012.0772
  • Odkaz: https://doi.org/10.1049/el.2012.0772
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A radiation and electro-magnetic (EM) field analysis of commercially available coaxial-to-coplanar transitions is presented. Radiation is quantified by measuring a crosstalk component between two Southwest microwave's transitions using a reflective planar calibration standard placed inside. Predictive simulation results are compared to the measured data and good agreement is reported. The proposed evaluation method is useful to evaluate quality of the transition and its radiation properties. Results can be used to estimate uncertainty budget of the calibrated measurement with respect to the measured radiation. Obtained results are promising to help further development of hardware or software solutions to suppress or minimize the radiation emerging from the launcher.

Verification technique of on-planar VNA calibration

  • Autoři: Morávek, O., Příhoda, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of 22nd International Conference Radioelektronika 2012. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2012. pp. 103-106. ISBN 978-80-214-4468-3.
  • Rok: 2012
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A novel approach of a quantitative verification of OSM calibration using innovative sliding load on a coplanar transmission line is proposed. Verification is done by measuring values of effective directivity e00eff on calibrated vector network analyzer (VNA). Modified absorber has been used as a sliding load to obtain satisfactory isolation and optimal reflection. Suitability of these absorbers as sliding load elements is discussed. Experimental verification of proposed method has been done and comparison of measured data to the simulated results is shown.

3D Modeling of Assembly Influence on Packaged Transistors

  • Autoři: Morávek, O., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 78th ARFTG Microwave Measurement Conference Proceedings. Piscataway: IEEE Microwave Theory and Techniques Society, US, 2011. pp. 24-29. ISBN 978-1-4673-0281-4.
  • Rok: 2011
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Detailed analysis of 70-mil package and wafer scale package (WSP) based on the 3D field simulations is presented. It is shown that an assembly plays significant role in the package behavior. Simulation results confirm that the parameters of the package are varying with the change of the assembly-substrate parameters. The approach potentially makes possible to transfer parameters of a transistor corresponding to certain assembly to another assembly without necessity of new measurements. It is very promising in the design of amplifiers namely power amplifiers (PA).

3D Modeling of Assembly Influence on Packaged Transistors

  • Autoři: Morávek, O., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Sborník semináře o řešení doktorského projektu Grantové agentury České republiky č. 102/08/H027 v roce 2011 - Pokročilé metody, struktury a komponenty elektronické bezdrátové komunikace. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2011. pp. 26-30. ISBN 978-80-214-4368-6.
  • Rok: 2011
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Achievements and work in progress from year 2011 are shown and discussed in this paper. This research is examining an assembly influences on packaged microwave transistors. Complex 3D electromagnetic simulations software is used to characterize the effects. Packages that were simulated are: Excelics 70-mil package and Avago Wafer Scale Package (WSP) which is used for the current VMMK transistor/amplifier range. Packages' dimensions were accurately measured and modeled accordingly. The assembly influence will be discussed while using four different substrates and two transmission lines. The effect of different surrounding environment for transistor package will be shown in the frequency range up to 40 GHz. The simulation results are verified by the measurements as well and good match is obtained.

A Method for Direct Impedance Measurement in Microwave and Millimeter-Wave Bands

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: IEEE Transactions on Microwave Theory and Techniques. 2011, 59(8), 2123-2130. ISSN 0018-9480.
  • Rok: 2011

Contactless Distance Measurement Method

  • DOI: 10.1109/ARFTG77.2011.6034559
  • Odkaz: https://doi.org/10.1109/ARFTG77.2011.6034559
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new method capable of contactless distance measurement with high resolution has been proposed. The method is intended to measure distance differences smaller than one half of a wavelength. First experimental results are reported. The method is based on precise phase evaluation of signal reflected by the surface whose distance is measured. This is achieved using interference between the reflected and reference signals. Micrometer resolution at 10 GHz can be expected.

Hidden Problems in Precise Calibration on Microstrip II Explanation and Solution

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Raboch, J.
  • Publikace: 78th ARFTG Microwave Measurement Conference Proceedings. Piscataway: IEEE Microwave Theory and Techniques Society, US, 2011, pp. 88-92. ISBN 978-1-4673-0281-4.
  • Rok: 2011
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A study of calibration problems on microstrip with respect to interaction of electromagnetic fields around coaxial to microstrip launch, microstrip line and microstrip calibration standards was carried out in frequency band up to 26 GHz. Omni Spectra SMA to microstrip launch, 50 microstrip line on Arlon CuClad 233 0.508 mm thick substrate and microstrip short, open and load as calibration standards were used for simulations in CST Microwave Studio. Multimode propagation in the whole structure making impossible application of standard calibration methods was discovered. A hardware solution enforcing only one mode propagation was designed and tested using a simulation testing method similar to standard calibration/verification procedure. Radical suppression of measurement uncertainties was achieved.

Improvement to Load-pull Technique for Design of Large-signal Amplifier in K Band

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    An improvement to the load-pull technique for a large-signal design of a transistor amplifier is proposed. On the contrary to the current load-pull technique - a small signal pre-matching on the output of the transistor is applied which results in reduced demands on a maximum VSWR of the tuner. This minimizes the launcher radiation in the K band and reduces measurement uncertainty. The proposed method has been verified on a design of 22 GHz large-signal amplifier using a Excelics EPA018A-70 transistor.

Microwave Impedance Measurement for Nanoelectronics

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The rapid progress in nanoelectronics showed an urgent need for microwave measurement of impedances extremely different from the 50Ω reference impedance of measurement instruments. In commonly used methods input impedance or admitance of a device under test (DUT) is derived from measured value of its reflection coefficient causing serious accuracy problems for very high and very low impedances due to insufficient sensitivity of the reflection coefficient to impedance of the DUT. This paper brings theoretical description and experimental verification of a method developed especially for measurement of extreme impedances. The method can significantly improve measurement sensitivity and reduce errors caused by the VNA.

New Multimode Planar Structure

  • Autoři: Příhoda, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 78th ARFTG Microwave Measurement Conference Proceedings. Piscataway: IEEE Microwave Theory and Techniques Society, US, 2011. pp. 118-121. ISBN 978-1-4673-0281-4.
  • Rok: 2011
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Described novel kind of multimode structure is suitable for planar aplications. In planar structures microstrip transmission line is very often used. Unfortunately E-field distribution of Q-TEM mode isn't suitable for some application. For example sliding load for microstrip line is the application where is used E-field outside the substrate. The E-field of Q-TEM mode is week outside the substrate in comparison with E-field in the substrate.

Study of Absorber Materials Usable on Microstrip and Their Attribute Improvements

  • Autoři: Příhoda, M., Morávek, O., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of 21st International Conference Radioelektronika 2011. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2011. pp. 345-347. ISBN 978-1-61284-322-3.
  • Rok: 2011
  • DOI: 10.1109/RADIOELEK.2011.5936448
  • Odkaz: https://doi.org/10.1109/RADIOELEK.2011.5936448
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A novel method for improving properties of absorber materials usable on a microstrip transmission line is proposed. Improvement is obtained by using a metallic sheets and changing a distribution of electric field along the absorber. Suitability of these absorbers as sliding load elements is discussed as well. Experimental verification of proposed modification has been done and comparison of measured data to the simulated results is discussed.

A Novel Method for Direct Impedance Measurement in Microwave and mm-Wave Bands

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 75th ARFTG Microwave Measurement Conference. Piscataway: IEEE Microwave Theory and Techniques Society, US, 2010. pp. 83-87. ISBN 978-1-4244-6365-7.
  • Rok: 2010
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A novel method for direct impedance measuremtn using a common vector network analyzer (VNA) is introduced.

Calculation of Maximal Applicable Gain for the Generalized and the Direct Method for Extreme Impedances Measurement

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 76th ARFTG Microwave Measurement Conference. Piscataway: IEEE Microwave Theory and Techniques Society, US, 2010. pp. 63-68. ISBN 978-1-4244-7448-6.
  • Rok: 2010
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A mathematical approach for determining the maximal applicable gain of amplifiers, that are used in two recently introduced methods for measurement of extreme input impedances using a common vector network analyzer (VNA) - the generalized method and the direct method - is presented. These two measurement methods exhibit outstanding measurement sensitivity for extreme impedance values - impedances significantly higher or lower than the 50Ů reference impedance of common measurement systems. The measurement sensitivity is better when gain of the used amplifiers is higher. However, the gain is limited by nonlinearity of the amplifiers and the receivers of the vector network analyzer. Therefore, the gain calculation is derived to make possible to fully exploit the capabilities of the measurement methods without loosing accuracy due to nonlinear effects. An example of calculation for one experimental setup is also presented.

Comments on "A Novel Vector Network Analyzer" Reply

Measurement of Extreme Impedances

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of 15th Conference on Microwave Techniques COMITE 2010. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2010. pp. 95-98. ISBN 978-1-4244-6351-0.
  • Rok: 2010
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This paper provides an experimental verification of a novel method for measurement of extreme impedances which was theoretically described earlier. In this paper experiments proving that the method can significantly improve stability of a measurement system are described. Using Agilent PNA E8364A vector network analyzer the method is able to measure reflection coefficient with stability improved 36-times in magnitude and 354-times in phase compared to the classical method of reflection coefficient measurement. Further, validity of the error model and related equations stated in the earlier paper are verified by real measurement of SMD resistors (size 0603) in microwave test fixture. Values of the measured SMD resistors range from 12 kΩ up to 330 kΩ. A novel calibration technique using three different resistors as calibration standards is used. The measured values of impedances reasonably agree with assumed values.

New Method Suitable for Relative Short Distance Measurement

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new method for relative short distance measurement of reflective surfaces was designed. The relative distance is derived from a frequency where two interfering coherent signals (one is reflected from the measured object, the second is a reference one) create a sharp signal minimum. The viability of the method was preliminary experimentally verified in X-band. Potential possibilities of the method were tested by software simulation. Sub-micron distance resolution in industrial applications can be supposed.

Generalized Method for Broadband Measurement of Extreme Impedances

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 74th ARFTG Microwave Measurement Conference - Digest. Piscataway: IEEE, 2009. p. 76-79. ISBN 978-1-4244-5713-7.
  • Rok: 2009
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This paper describes generalization of a method for extreme impedances measurement published in [1] and [2]. The transmission coefficient measured by a vector network analyzer (VNA) results from summation or difference between reflection coefficients of a reference and measured impedance. The resulting signal is then amplified by an amplifier in order to gain very high resolution of impedances. Two types of wideband passive 4-port network solutions were designed and tested. With current components frequency band 0.7 - 10 GHz was achieved.

Microwave Radar Sensors for Active Defense Systems

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Modern anti-armor missiles represent enormous threat for any military vehicle. Simple hand-held missiles are able to penetrate 300 mm, more sophisticated missiles up to 1000 mm of the best steel armors. Active defense methods seem to be promising ways how to face this problem. Systems of active defense are based on sensors able to detect and measure approaching threat missile and generate signals that activate a suitable counter-measure. The paper describes several different designed radar sensors tested in active defense configurations. This concerns narrowband sector sensor, "microwave curtain" and a new wideband sensor with a distance measurement capability. All practical tests were performed using real missiles at army shooting ranges.

Microwave Vector Measurements

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 19th International Traveling Summer School on Microwaves and Lightwaves - Proceedings. Rome: University of Rome "Tor Vergata", 2009. pp. 242-263.
  • Rok: 2009
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Microwave vector measurements, basic principles of vector network analyzers, calibration and correction methods, single ended and differential measurement, measurement of multi - ports.

A Simple Method for Extreme Impedance Measurement - Experimental Testing

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 72nd ARFTG Microwave Measurement Symposium Fall 2008 - Proceedings. Piscataway: IEEE, 2008. p. 40-44. ISBN 978-1-4244-2299-9.
  • Rok: 2008
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This paper directly follows and extends [1] where a novel method for measurement of extreme impedances is described theoretically. It is experimentally proved that the method [1] can significantly improve stability of a measurement system. Error model and equations in [1] are verified by real measurement. A novel calibration technique using three different resistors as calibration standards is used. [1] M. Randus, K. Hoffmann, "A simple method for extreme impedances measurement," 2007 ARFTG Int. Conference, 2007.

Design of SMA 50 Ohm Load Using 3D EM Field Simulator: Comparison with Reality

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of the 14th Conference on Microwave Techniques COMITE 2008. Praha: Československá sekce IEEE, 2008. p. 313-316. ISBN 978-1-4244-2137-4.
  • Rok: 2008
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The subject of this paper is to provide a comparison of 3D EM field simulation results of 0603 size SMD resistors with corresponding real data obtained by precise vector measurements. The simulated results were obtained by 3D EM field simulator CST Microwave Studio with time-domain solver. The comparison is shown on a design of an optimized 50? load composed of a common SMA flange connector and a set of 0603 size SMD resistors. The resistors are soldered between the inner conductor of the coaxial SMA connector and the flange. Several arrangements of the SMD resistors ranging from single-resistor arrangement to four-resistor pattern as well as different orientation of the resistive layer of the SMD resistors are discussed. Step discontinuity of the inner conductor of a real SMA connector is subsequently also involved in 3D EM field simulation and these results are compared with precise vector measurements.

Errors in Measurement of Microwave Interferograms Using Antenna Matrix

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    New antenna matrices for both scalar and vector measurement of microwave interferograms for the frequency 2.45 GHz were developed and used for an analysis of sources of measurement errors. Influence of mutual coupling between individual antennas in an antenna matrix on a measurement of microwave interferograms, particularly on a measurement of interferogram minimum values, was studied. Simulations and measurements of interferograms, proposal of a new calibration procedure and correction method are presented. Influence of differences in radiation patterns of individual antennas of an antenna matrix on a measurement of microwave interferograms was studied as well.

Hidden Problems in Precise Calibration on Microstrip

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A study of calibration problems on microstrip with respect to interaction of electromagnetic fields around SMA to microstrip launcher and microstrip short was carried out in frequency band up to 26 GHz. Omni Spectra SMA to microstrip launcher, 50 Ω microstrip line on Arlon CuClad 223 0.508 mm thick substrate and microstrip shorts with reflective wall above the upper side of substrate as a calibration elements were used for simulations in CST Microwave Studio. Strong influence of dimensions of shorts and distance between the shorts and the launcher on simulated calibration data was observed. Reasonable dimensions of the short and the distance between the short and the launcher making possible correct precise calibration were determined.

Microwave Vector Measurements

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 18th International Travelling Summer School on Microwave and Lightwaves - Proceedings. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2008. pp. 154-187.
  • Rok: 2008

Parametric Equivalent Circuit of Single Layer Capacitor Mounted in Microstrip Line

  • Autoři: Raboch, J., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of the 14th Conference on Microwave Techniques COMITE 2008. Praha: Československá sekce IEEE, 2008. pp. 309-312. ISBN 978-1-4244-2137-4.
  • Rok: 2008
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    3-D EM simulator based equivalent circuit of a Single Layer Capacitor (SLC) mounted on 50 Ω microstrip line of Arlon CuClad233 substrate was derived. The circuit corresponds to substrate thickness ranging from 0.254 mm to 1.270 mm and frequency range 45 MHz - 26 GHz. Values of equivalent circuit components determined by equations are dependent on substrate thickness.

Radar Sensor for Detection and Measurement of Anti-Armour Missiles

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Přednáška je zaměřena na popis problematiky měření dvou základních typů protipancéřových střel v mikrovlnném frekvenčním pásmu. Popsány jsou vlastnosti a konstrukce úzkopásmového a širokopásmového senzoru, uvedeny jsou příklady měření provedených na armádních střelnicích s použitím reálných střel.

Radar Sensor for Detection of Anti-Armour Missiles

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The anti-armour missiles represent one of the biggest threads for any military vehicle, both in a standard combat or e.g. during UN humanitarian as well as peacekeeping operations. Millions of extremely dangerous missiles, able to break-through even tank armour-plates, are widely spread even in the world's most dangerous hot spots and geostrategic areas. Standard lighter vehicles and helicopters alike do not have, by themselves, any chance against them. As a result, the possibly more efficient methods of defense against them are under scrutiny and are subject to a continuous development. Active defense methods are based on a detection of the thread missiles and activation of an efficient counter-measure. The presented paper describes parameters of two most dangerous missiles and calculates parameters decisive for their detection in microwave frequency range. The practical measurements verify and confirm the calculated detection parameters.

A Scalar Microwave Interferometric Measurement System for Nondestructive Testing

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    In this contribution is presented design and realization of a new scalar microwave interferometric measurement system and results obtained with this measurement system.

A Simple Method for Extreme Impedances Measurement

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceeding of the 70th ARFTG Microwave Measurements Conference. Piscataway: IEEE Microwave Theory and Techniques Society, US, 2007. p. 46-50.
  • Rok: 2007
  • DOI: 10.1109/ARFTG.2008.4804276
  • Odkaz: https://doi.org/10.1109/ARFTG.2008.4804276
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper describes a new method for measurement of extreme impedances - impedances with a magnitude of the corresponding reflection coefficient approaching unity. The proposed method employs a common vector network analyzer (VNA) with a reference impedance of 50 Ω or 75 Ω. The method is based on subtracting a reference reflection coefficient from a reflection coefficient of the device under test (DUT) by a 180-deg 3dB hybrid coupler. This difference is then amplified and measured by the VNA as a transmission coefficient. The method was experimentally verified in frequency band from 1.5 to 3 GHz. A corresponding calibration and correction method is suggested. Applications of the method can be expected in measurements of emerging novel microwave and THz devices based on carbon nanotubes, whose impedances are in orders of tens or hundreds of kΩ.

Broadband Medium-Power Transistor Amplifier 12-18 GHz

  • Autoři: Randus, M., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of 17th International Conference Radioelektronika 2007. Brno: FEKT VUT v Brně, 2007. pp. 307-311. ISBN 978-1-4244-0821-4.
  • Rok: 2007
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A medium-power two-stage transistor microwave amplifier for frequency band of 12 to 18 GHz using eight packaged HEMTs has been designed and developed. Gain over 16 dB, output power P-1dB > 22 dBm and return loss better than 10 dB both on the input and output has been achieved in the whole band. The input and output are DC grounded to protect the amplifier from electrostatic discharge (ESD). Mutually linked AWR Microwave Office circuit simulator, 3D EM field simulator CST Microwave Studio and precise small-signal s-parameters vector measurements were used for the design.

Generalized Approach for Phase Interferometric Measurements of Electromagnetic Field

  • DOI: 10.2529/PIERS070520090330
  • Odkaz: https://doi.org/10.2529/PIERS070520090330
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new generalized approach for microwave phase interferometric measurement of electromagnetic field using an antenna matrix (AM) was developed. The approach allows correction of most significant measurement errors caused by mutual couplings of closely spaced antenna elements. It is based on vector measurements of the AM designed for the frequency 2.60 GHz and Matlab simulations.

Generalized Approach for Phase Interferometric Measurements of Electromagnetic Field

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new generalized approach for microwave phase interferometric measurement of electromagnetic feld using an antenna matrix (AM) was developed. The approach allows correction of most signifcant measurement errors caused by mutual couplings of closely spaced antenna elements. It is based on vector measurements of the AM designed for the frequency 2.60 GHz and Matlab simulations.

Generalized Approach for Phase Interferometric Measurements of Electromagnetic Field

  • DOI: 10.2529/PIERS070520090330
  • Odkaz: https://doi.org/10.2529/PIERS070520090330
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new generalized approach for microwave phase interferometric measurement of electromagnetic field using an antenna matrix (AM) was developed. The approach allows correction of most significant measurement errors caused by mutual couplings of closely spaced antenna elements. It is based on vector measurements of the AM designed for the frequency 2.60 GHz and Matlab simulations.

Restrictions in Using Large Signal and Small Signal Models of FET Transistors

  • Autoři: Raboch, J., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of 17th International Conference Radioelektronika 2007. Brno: FEKT VUT v Brně, 2007. pp. 607-610. ISBN 978-1-4244-0821-4.
  • Rok: 2007
  • DOI: 10.1109/RADIOELEK.2007.371674
  • Odkaz: https://doi.org/10.1109/RADIOELEK.2007.371674
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A frequency doubler from 8.5 to 17 GHz was used to study reliability and accuracy of large signal Curtis Cubic model of HEMT transistor. Excelics EPA018A-70 was used for the tests. Two large signal designs and realizations for working points in class B and open state (near Idss ) were made. Another design based on measured small signal s-parameters only was done for comparison, too. AWR Microwave Office was used for simulations. All designs were realized and measured. Significant discrepancies between simulated and measured parameters for Curtis Cubic model operated in class B were observed.

Short-Range Detection and Measurment of Small High-Speed Objects in Microwave Frequency Region

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Systems of active defense of vehicles or buildings are based on detection and measurement of potentially dangerous anti-armor missiles. Radar measurement of these missiles is complicated by their usually very low radar cross-section (RCS) values. Knowledge of RCS values plays crucial role in design of reliable detection system. The purpose of this paper is to present first results of 3D electromagnetic field simulations of accurate models of two common types of anti-armor missiles. The results are discussed with respect to the impact on detection and measurement range of active-defense systems.

Vector Measurement of Microwave Interferograms with Antenna Matrix

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new antenna matrix for vector measurements of microwave interferograms at frequency 2.4 GHz was developed. Influence of mutual couplings between antennas in the antenna matrix on measurement of microwave interferograms, particularly on measurement of their minimum values was studied. A simulation of corresponding measurement errors based on measurement of a real antenna matrix, proposal and experimental verification of a new calibration and correction method are presented as well.

A New Scalar Microwave Interferometric Measurement System

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new scalar network analyzer system with an antenna matrix for microwave interferometric measurement was realized on frequency 2.45 GHz. Experimental results are compared with interferometric measurement using vector network analyzer (VNA) and an antenna x-y positioning system. The new system is supposed to be used in non-contact deformation and non-homogeneity measurements in civil engineering and other similar areas.

A Novel Vector Microwave Phase Interferometer

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper describes a concept of a novel vector microwave phase interferometer based on a vector network analyzer system. The instrument is designed for fast vector measurements of a space distribution of an interference electromagnetic field using a matrix of antennas. It is supposed to be used in non-contact deformation and non-homogenity measurements in civil engineering and other areas. Results of first measurements performed in the 2.45 GHz frequency band are presented.

Improved Evaluation of Planar Calibration Standards Using TDR Preselection Method

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Calibration and correction methods for Vector Network Analyzer (VNA) are based on the fundamental assumption of constant error model, which is independent of connected calibration standards and/or devices under test (DUT). Unfortunately, this assumption is not satisfied well for planar calibration standards fabricated by etching technology on soft substrates. An evaluation of the error etching technology on soft substrates. An evaluation of the error model is affected expecially with a variation of the manufacturing process and also with a reproducibillity of an assembly. In this paper, we propose error minimazation using selection of the best combination of available calibration standards based on time-domain reflection (TDR) measuerment. The proposed method was verified experimentally using short, open, load and thru (SOLT) standards fabricated on FR4 laminate substrate getting essential reduction of the measurement error in frequency range up to 15 GHz.

Vector Network Analyzer for Microwave Interferometry Measurement

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper describes a concept of a novel vector microwave phase interferometer based on a simple vector network analyzer. It is supposed to be used in non-contact deformation and non-homogeneity measurements in civil engineerign and other areas.

7 State PTP for Vector Network Analyzer

  • DOI: 10.1109/ARFTGS.2005.1500583
  • Odkaz: https://doi.org/10.1109/ARFTGS.2005.1500583
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new, 7 state switched perturbation two-port (PTP) for vector measurement based on scalar measurement only was designed and realized in microstrip structure using PIN diodes. The structure was experimentally tested by means of vector measurements of different impedances in frequency band with relative bandwidth of 2.5 octave. Good agreement with data obtained using a precise vector network analyzer was achieved.

7 State PTP for Vector Network Analyzer

  • Autoři: Závodný, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: The 13th Conference on Microwave Techniques - COMITE 2005. Praha: IEEE Czechoslovakia Section, 2005. pp. 175-178. ISBN 80-86582-16-7.
  • Rok: 2005
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new, 7 state switched perturbation two-port (PTP) for vector measurement based on scalar measurement only was designed and realized in microstrip structure using PIN diodes. The structure was experimentally tested by means of vector measurements of different impedances in frequency band with relative bandwidth of 2.5 octave. Good agreement with data obtained using a precise vector network analyzer was acheived.

A New Concept of PTP Vector Network Analyzer

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The novel 7-state PTP consists of switched elementary two ports composed from thru connection and serial and parallel RC, RL and R combinations connected to 50W microstrip line. It was designed for the frequency band 240-1600 MHz. The structure and the values of components of this PTP were optimized using the new test criteria. Corresponding quadratic planes are shown. The elements were chosen so that the individual quadratic planes were sufficiently different in the whole frequency band.

A Selective I/Q Demodulator with High Dynamic Range for Microwave Interferometer

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The paper describes a basic concept of a novel microwave phase interferometer based on a multi-port vector network analyzer (VNA). A block diagram of the designed system is presented. The main goal of this paper is to describe the crucial part of the microwave interferometer - the selective I/Q demodulator - with high dynamic range. An experimental verification of the designed I/Q demodulator is presented.

Assembly Influence on S-Parameters of Packaged Transistor

  • DOI: 10.1109/ARFTGS.2005.1500579
  • Odkaz: https://doi.org/10.1109/ARFTGS.2005.1500579
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A proper analysis of the assembly influence on small-signal parameters of packaged transistor has been done. The S-parameters differences caused by assembly change are computed using the standard method and three new proposed methods that exploit 3-D model of the transistor package. The differences, accuracy and suitability of these methods are discussed. The results were verified experimentally for particular packaged transistor in frequency range 45 MHz - 18 GHz.

Assembly Influence on the Small-Signal Parameters of a Packaged Transistor

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A detailed analysis of the assembly influence on the small-signal parameters of a packaged transistor is presented. A new method, based on 3D field simulation and mixed-mode scattering parameters approach is proposed. Differences in scattering parameters caused by assembly change are computed using the new proposed method and compared to the standard method based on admittance matrix. The differences, accuracy, error sources and suitability of both methods are discussed. Results are verified experimentally in microstrip line for two fundamental assembly change of a transistor in SOT 343 package in frequency range 45 MHz - 18 GHz.

Microwave Measurements of Radio Interference Filters

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Scalar and vector measurement methods for testing of multi-port radio interference filters for shielded chambers are designed. The method make possible to measure the filters in frequency band from DC-3 GHz. At the time being there is no acceptable standard for these multi-oort measurements.

Seven State PTP for Vector Network Analyzer

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new, 7 state switched perturbation two-port (PTP) for vector measurement based on scalar measurement only was designed and realized in microstrip structure using PIN diodes. The structure was experimentally tested by means of vector measurements of different impedances in frequency band with relative bandwidth of 2.5 octave. Good agreement with data obtained using a precise vector network analyzer was achieved.

Zobecněný přístup k měření v mikrovlnné oblasti

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

7-State Perturbation Two Port

  • Autoři: Závodný, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Conference Proceedings of Radioelektronika 2004. Bratislava: Slovak University of Technology, 2004. pp. 273-276. ISBN 80-227-2017-8.
  • Rok: 2004
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A novel construction of 7-state perturbation two port vector network analyzer is presented. It consist of 7 basic passive two port discontinuities which enable a simple realization with good electrical parameters at certain parts of Smith chart. The new approach makes possible to choose the best states for specific area in Smith Chart. A mathematical background of the approach and new test criteria are designed.

A New concept of PTP Vector Network Analyzer

Assessment of Reference Planes Location for 3-D Components in Planar Structures

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    An appropriate reference plane location is the key issue of correct modeling of microwave circuits. A new method for the reference plane location assessment is proposed. The examples of stand-alone 3-D components as rell as for components in proximity of other 2-D or 3-D discontinuity. The reference plane location is strongly dependent on class of discontiuity laying in proimity of the component.

First results of microwave measurement of broadband radio interference filters

Mikrovlnná technika - výzkum, vývoj

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Sborník vzdělávacích a vědeckovýzkumných činností a nabídek. Praha: IEEE Czechoslovakia Section, 2004. pp. 13-15. ISBN 80-86582-15-9.
  • Rok: 2004

Novel Broadband Vector Microwave Measurement Methods

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Multistate reflectometers represent an alternative to expensive network analyzers. This paper describes two particular instruments developed at the FEE CTU in Prague. One extends the classic scalar network analyzer by means of a special designed Perturbation Two-Port (PTP) while the second suggests a completely new circuitry for the detector as well as the linear variable part.

On the Perpendicular Coax-Microstrip Transition

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    The perpendicular coax-microstrip transition was studied using two kind of standard SMA connectors. A A generalized equivalent circuit along with parameter for Arlon 25a substrate is proposed. The low-pass nature, parasitic resonance and unwanted radiation of a perpendicular transition are demonstrated. Simulated data were verified by measurement in the frequency range 0.045-15 GHz.

Perspective Microwave Vector Measurement Methods

  • Autoři: Závodný, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: ITSS 2004 - Summer School Proceedings. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2004. pp. 370-376.
  • Rok: 2004

Practical Realizations in Microwave Technique

  • Autoři: Závodný, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of Workshop 2004. Praha: České vysoké učení technické v Praze, 2004. pp. 462-463. ISBN 80-01-02945-X.
  • Rok: 2004
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Filters play an important role in many RF microwave applications. Emerging applications such as wireless communications continue to challenge RF microwave filters with ever more stringent requirements of higher performance, smaller size and lower cost. Because of these requirements, we have decided to integrate into our new educational program a subject called /Practical Realizations in Microwave Technique/. This program is recommended for students interested in planar microwave circuits, microwave measuring techniques and microwave simulation software tools, and at present improves the amount of hands-on exercises at the Laboratory of microwave, optical and antennas techniques.

Precise Wideband Microwave Measurements

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: ITSS 2004 - Summer School Proceedings. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2004. pp. 94-125.
  • Rok: 2004

Tunable Low Pass Coaxial Filter

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Microwave system designs have traditionally depended on passive circuit filter implementations, involving tradeoffs between filter performance and size. There are many types of filter constructions and also many design possibilities. Because of this situation, it has been decided at the department to incorporate into our new educational program at Laboratory of microwave optical and antennas techniques a new project called /Tunable Low-Pass Coaxial Filter/. The main purpose of this project is to familiarize students with the design procedures and realizations of the most typical coaxial microwave low pass filters, as well as with their measurement. This project is innovative in a technical and in a pedagogical sense: a teaching, learning and evaluating methodology.

Vector Measuring with 7-state Perturbation Two Port

  • Autoři: Závodný, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Sborník příspěvků konference RADEŠÍN 2004. Brno: FEKT VUT v Brně, 2004. pp. 127-128. ISBN 80-214-2726-4.
  • Rok: 2004
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A novel construction of 7-state perturbation two port vector network analyzer is presented. It consist of 7 basic passive two port discontinuities which enable a simple realization with good electrical parameters at certain parts of Smith chart. The new approach mokes passible to choose the best states for specific area in Smith Chart. A mathematical baksground of the approach and new test criteria are designed.

Zobecněný přístup k problematice měření v mikrovlnné technice

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

A Correction of the Noise Figure Measurement for Highly Mismatched DUT

  • Autoři: Sokol, V., prof. Ing. Karel Hoffmann, CSc., Vajtr, J.
  • Publikace: 11th Microcoll - Proceedings. Budapest: Hungarian Academy of Sciences, 2003. pp. 123-126. ISBN 963-212-166-X.
  • Rok: 2003
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Device mismatch seriously degrades accuracy in noise figure characterization. The second stage correction technique for highly mismatched DUT is proposed and compared to standard technique. Significant accuracy improvement of measured data is presented.

A Novel 3-D Ultrawideband Balun

  • Autoři: Sokol, V., prof. Ing. Karel Hoffmann, CSc., Vajtr, J.
  • Publikace: COMITE 2003. Praha: IEEE Czechoslovakia Section, 2003. pp. 89-92. ISBN 80-86582-09-4.
  • Rok: 2003
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A novel 3-D ultrawideband balun was designed and manufactured. The VIP structure provides good performance in frequency range 2-20 GHz. Out-of-phase-shifted outputs are available on the same side of the substrate. A reasonable agreement between measurement and simulationwas achieved.

Improvement of Microstrip Open-end Calibration

  • Autoři: Sokol, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Radioelektronika 2003 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2003. pp. 245-248. ISBN 80-214-2383-8.
  • Rok: 2003
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Microstrip open-end at the edge of the substrates a calibration element was studied. The fringing capacitance was computed for several commonly used substrates. Decreased phase error of vector measurement on 50? microstrip line up to 8 degrees at 26 GHz can be expected.

Mikrovlnná techniky - výzkum, vývoj

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Sborník vzdělávacích a vědeckovýzkumných činností a nabídek katedry elektromagnetického pole FEL ČVUT. Praha: Československá sekce IEEE, 2003. p. 17-21. ISBN 80-86582-13-2.
  • Rok: 2003

Monofrekvenční generátor 25 GHz

  • Autoři: Vajtr, J., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Odborné semináře - Sborník za rok 2002/2003. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2003. pp. 17-22. ISBN 80-86582-12-4.
  • Rok: 2003
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Byl navrhnut a následně i vyroben generátor na kmitočtu 25 GHz. Při jeho konstrukci byla použita metoda kaskádního řazení dvojbranů. Generátor umožňuje práci ve dvou režimech - kontinuální a 1 kHz modulace. Dosažená úroveň výstupního signálu je větší než 2 dBm.

Noise Figure Measurement of Highly Mismatched DUT

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A device mismatch seriously degrades the accuracy of its noise figure characterization. A new second stage correction technique for highly mismatched device under test is proposed and compared to the standard technique. The presented method is based on additional vector measurement. It takes into account measuring receiver noise figure dependence on the DUT output mismatch besides an available gain correction. Significant accuracy improvement of measured data and decreased error variation is demonstrated. The suggested method is in principle able to eliminate all systematic errors in noise figure measurement.

On Radio Interference Filter Measurement

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A new measurement method for on site testing of multiport radio interference filters (RIF) on shielded chamber is designed. The method is based on scalar measurement only and makes possible a pessimistic estimate of the filters damping in frequency band from DC-3GHz. More than 120 dB dynamic of measurement can be expected. At the time being there is no acceptable standard for these multiport measurements.

Wideband VIP Power Divider with Differential Output

  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    A novel wideband VIP power divider with out of phase outputs was designed and experimentally verified. The phase difference 180°- 5°and the amplitude difference 0.8 dB of output signals were achieved in 4-26 GHz frequency band. Common ground of all coaxial ports is advantageous for application of the component in some differential measurements.

3D Vertical Stub on Microstrip Line

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Sokol, V.
  • Publikace: Radioelektronika 2002. Bratislava: Slovak University of Technology, Faculty of Civil Engineering, 2002. pp. 378-381. ISBN 80-227-1700-2.
  • Rok: 2002

Analysis of 3D Vertical Stub on Microstrip Line

  • Autoři: Sokol, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 32nd European Microwave Conference Proceedings. London: CMP Europe Ltd, 2002. pp. 569-572. ISBN 0-86213-208-8.
  • Rok: 2002

Analýza 3D vertikálního pahýlu v mikropáskovém vedení

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Sokol, V.
  • Publikace: WORKSHOP - Grantové fórum. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. pp. 74-75. ISBN 80-86582-06-X.
  • Rok: 2002

Microwave GaAs Schottky Diode

  • Autoři: Macháč, P., Jeníček, V., Pangrác, J., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: ASDAM 2002. Bratislava: IEEE, 2002. p. 125-128. ISBN 0-7803-7276-X.
  • Rok: 2002
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    This contribution deals with the technological realization of a special GaAs Schottky diode, based on the side-by-side technique. This is a structure, where one of the dimensions of the Schottky contact is given by the thickness of the epitaxial layer on which the structure is fabricated We reached the value of cut-off frequency 13 GHz; this is in discrepancy with the theoretically predicted parameters, This contribution points to the weakness of the suggested theory and describes the technological improvements, which should lead to increased limiting frequency.

Mikrovlnná technika - výzkum a vývoj

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: WORKSHOP - Vzdělávací fórum - nabídka aktivit. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. p. 52-54. ISBN 80-86582-07-8.
  • Rok: 2002

Model solenoidu nad zemní rovinou

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Vajtr, J.
  • Publikace: WORKSHOP - Grantové fórum. Praha: ČVUT FEL, Katedra elektromagnetického pole, 2002. pp. 76-77. ISBN 80-86582-06-X.
  • Rok: 2002

A Model of Solenoid above Ground Plane

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Vajtr, J.
  • Publikace: COMITE 2001. Praha: IEEE Czechoslovakia Section, 2001. pp. 149-152. ISBN 80-902417-9-4.
  • Rok: 2001

Active Microwave and millimeterwave Resonator

Active Resonator

Arbitrary Q-Factor Dielectric Resonator

New Measurement Method for Characteristic Impedance Determination

Robust Measurement Method for Bus-line Characteristic Impedance Determination on Microwave Frequencies

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: MIOP 2001 - The German Wireless Week. Hagenburg: Network, 2001. pp. 139-141. ISBN 3-924651-91-4.
  • Rok: 2001

Solenoid above Ground Plane - Equivalent Circuit

Vector Measurement of Single-ended and Balanced Devices

Wide-band Transistor Power Amplifier 1,8 - 8,6 GHz

  • Autoři: Rybář, F., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Radioelektronika 2001 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2001. pp. 74-77. ISBN 80-214-1861-3.
  • Rok: 2001

A Planar Broadband Balanced Frequency Doubler

  • Autoři: Sokol, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Radioelektronika 2000 - Conference Proceedings. Bratislava: STU v Bratislave, FEI, 2000. pp. P-94-P-95. ISBN 80-227-1389-9.
  • Rok: 2000

Equivalent Circuit of SMD Resistors 0603 Valid up to 12 GHz

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Radioelektronika 2000 - Conference Proceedings. Bratislava: STU v Bratislave, FEI, 2000. pp. IV-58-IV-61. ISBN 80-227-1389-9.
  • Rok: 2000

Measurement Method for Microwave Line Characteristic Impedance Determination

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Workshop CAD&CAE 2000. Prague: Czechoslovakia Section IEEE, 2000. pp. 5-7. ISBN 80-902417-6-3.
  • Rok: 2000

Microwave Vector Measurement

Mikrovlnné obvody pro radiokomunikační systémy

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Radiokomunikace 2000. Praha: ČVUT FEL, Katedra radioelektroniky, 2000. p. 563-592. ISBN 80-01-02142-4.
  • Rok: 2000

Vector Measurements in Physically Inaccessable Reference Planes

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Proceedings of Workshop 2000. Praha: České vysoké učení technické v Praze, 2000. pp. 212. ISBN 80-01-02229-3.
  • Rok: 2000

Equivalent Circuit of Microwave Package

  • Autoři: Šaman, H., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: The 10th Conference on Microwave Techniques COMITE 1999. Prague: Czechoslovakia Section IEEE, 1999. pp. 91-93. ISBN 80-902417-3-5.
  • Rok: 1999

Equivalent Circuit of SMD Resistors 0805 up to 12 GHz

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: 9th International Czech-Slovak Scientific Conference Radioelektronika 99. Brno: VUT v Brně, 1999. pp. 267-270. ISBN 80-214-1327-1.
  • Rok: 1999
  • Pracoviště: Katedra elektromagnetického pole
  • Anotace:
    Equivalent Circuit of SMD Resistors 0805 up to 12 GHz valid for microstrip line on CuClad 0.5 mm substrate and 50 oms line

Equivalent Circuit of SMD Resistors 0805-Influence of Mounting

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: The 10th Conference on Microwave Techniques COMITE 1999. Prague: Czechoslovakia Section IEEE, 1999. pp. 85-88. ISBN 80-902417-3-5.
  • Rok: 1999

Microstrip Coupling Structure for Tight Coupling

Microwave Part of Alert Receiver

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Vozáb, J., Čech, P.
  • Publikace: Vedecko-technický rozvoj letectva a protivzdušnej obrany. Košice: Vojenský letecký technický a skúšobný ústav, 1999. pp. 99-103.
  • Rok: 1999

A Novel Vector Network Analyzer

Calibration of the PTP Vector Network Analyzer

Cost-effective Vector Measurement

Novel Vector Network Analyzer

HP 8410-PC Controlling System and PTP Vector Analyzer

HP 8410-PC Controlling System v. 4.1

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Workshop CAD and CAE 97. Praha: ČVUT FEL, Katedra elektromagnetického pole, 1997. pp. 7. ISBN 80-902417-1-9.
  • Rok: 1997

Method of Vector Measurement Using Scalar Analyser

  • Autoři: Klusáček, V., prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Workshop 97. Praha: České vysoké učení technické v Praze, 1997. pp. 943-944.
  • Rok: 1997

Microwave Transistor Catalogue Data vs. Measured Data

Microwave Transistor Data: Catalogue vs. Measurement

MTR-2 Correction Method for FET Measurements Based on a 4-Port Error Model Including Crosstalks

Řídicí systém HP8410-PC verze 4.1

  • Autoři: prof. Ing. Karel Hoffmann, CSc., Jedlička, J.
  • Publikace: Workshop CAD&CAE 96. Praha: ČVUT FEL, Katedra elektromagnetického pole, 1996. pp. 3-5.
  • Rok: 1996

The Material Dielectric Characteristic Measurement

Vector Measurement With Scalar Analyzer

Vector Measurement with Scalar Only Analyzer

A Novel Method of Vector Measurement Using Scalar Analyzer

Automatic PC Controlled Vector Analyzer with HP 8410

Correction Method for Non-Coaxial Test Fixtures with Limited Number of Calibration Elements

Koplanární vedení-nové vztahy pro korekci na tloušťku pokovení

On the Impedance of Parallel Plate Guides

Vector Measurement Using Scalar Sensor Only

Vector Measurement with Scalar Analyzer

Vector Measurement with Slalar Analyzer

Calculation of a Power Field in Electric Glass Melting Furnace

Correction Methods for Vector Network Analyzers

  • Autoři: prof. Ing. Karel Hoffmann, CSc.,
  • Publikace: Microwave, Millimeter-Wave and Optical Electronics. Darmstadt: Institute for High-Frequency Electronics, 1994. pp. 103-119.
  • Rok: 1994

New Correction Methods for Non-coaxial Test Fixtures

Calculation of a Power Field in Lectric Glass Melting Furnace

Computer Aided Design of Radiofrequency and Microwave Circuits

New Correction Methods for Non-coaxial Test Fixtures

Za stránku zodpovídá: Ing. Mgr. Radovan Suk