Lidé

prof. Ing. František Vejražka, CSc.

Všechny publikace

Concurrent Bi-directional TDoA Positioning in UWB Network with Free-running Clocks

  • DOI: 10.1109/TAES.2022.3161895
  • Odkaz: https://doi.org/10.1109/TAES.2022.3161895
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper proposes an approach of TDoA positioning in UWB networks, where user tags localize themselves by means of exploitation of the broadcasted synchronization messages of the anchor network. Such approach promises unlimited number of localized devices, moreover, the position is available directly at the user terminal. The key challenge of this method is to eliminate errors caused by tag clock drifts, which render the TDoA measurements useless when left uncorrected. Our method employs extended Kalman filtering (EKF) for the estimation of position and elimination of the drift-induced errors. It is shown that the system performance is similar to the more common TDoA method, where the tags transmit blinks received by the anchors. However, the anchors are still able to receive the blink messages and estimate position of those tags, since the synchronization messages are exploited. Therefore, it is possible to use both directions of the TDoA positioning concurrently; a limited number of tags is tracked by the infrastructure and all tags may compute their positions. The TDoA solutions have achieved RMS horizontal accuracy of 25.9 cm and 33.6 cm, respectively.

An Accurate and Efficient Computation of Poles and Zeros of Transfer Functions for Large Scale Analog Circuits and Digital Filters

  • DOI: 10.1007/978-981-15-9209-6_8
  • Odkaz: https://doi.org/10.1007/978-981-15-9209-6_8
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The poles and zeros of a circuit transfer function can be efficiently computed solving the generalized eigenvalue problem, which could be transformed into the standard eigenvalue problem to be solved by a suitably modified QR algorithm. In this way, the poles and zeros can be obtained for any linear circuit or a nonlinear circuit linearized at an operating point (using the Laplace transform), or for any digital filter (using the Z transform). Both the reduction of the generalized eigenvalue problem to the standard form and the iterative procedures of the QR algorithm are very sensitive to the numerical precision of all calculations. The numerical accuracy is especially critical for the two kinds of circuits: the microwave circuits characterized by huge differences among the magnitudes of the poles and zeros, and the large scale circuits, where the errors of poles and zeros are increased by the extreme number of arithmetic operations and frequent multiplicity of the poles and zeros as well. In this chapter, two illustrative examples of the reduction of the general eigenvalue problem (the first for analog and the second for digital circuit) and using the QR algorithm are shown first. After that, four circuits of various sizes are analyzed: simpler microwave low noise amplifier, larger power operational amplifier, more complex example with a 272 integrated operational amplifier, and the most difficult analysis of a distributed oscillator. A meticulous comparison of the obtained results shows that a usage of newly implemented 128-bit arithmetics in GNU Fortran or C compilers with partial pivoting can assure both efficient and enough accurate procedures for computing the poles and zeros of the circuit transfer function.

Joint Acquisition Estimator of Modern GNSS Tiered Signals Using Block Pre-Correlation Processing of Secondary Code

  • DOI: 10.3390/s20102965
  • Odkaz: https://doi.org/10.3390/s20102965
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Objective is a joint primary and secondary code (SC) acquisition estimator of tiered Global Navigation Satellite Systems (GNSS) signals. The estimator is based on the Parallel Code Search algorithm (PCS) combined with the Single-Block-Zero-Padding (SBZP) and the Pre-correlation Coherent Accumulation (PCA). The PCA realizes the extension of the coherent integration time in front of the PCS. However, the PCS with the SBZP and the PCA is affected by a navigation/SC bit transition problem due to its cyclic property of a computed Cross-Ambiguity Function (CAF). This CAF is degraded by diverse parasitic fragments and is not directly applicable for an acquisition. A novel analysis of this mechanism and its impact is presented. Then, the proposed modified SBZP (mSBZP) modified PCA (mPCA) PCS estimator is constructed, which does not degrade the CAF. The mSBZP allows the use of the PCS algorithm in the presence of SC bit transition, while the mPCA decreases the number of PCS algorithm calculations by a factor of SC chip count due to SC pre-correlation processing. The algorithm has the same detection performance in comparison with conventional Double-Block-Zero-Padding (DBZP). However, it allows using the PCS of half-length with longer latency up to a factor of SC chip count

Novel Partial Correlation Method Algorithm for Acquisition of GNSS Tiered Signals

  • DOI: 10.1002/navi.390
  • Odkaz: https://doi.org/10.1002/navi.390
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper presents a new modified Single Block Zero-Padding (mSBZP) Partial Correlation Method (PCM) Parallel Code Search (PCS) algorithm for effective acquisition of weak GNSS tiered signal using coherent processing of its secondary code (SC) component. Two problems are discussed: acquisition of primary codes with longer period using FFT blocks of limited length, and the utilization of PCS in the presence of SC bit transition. The PCM and SC bit transition forms parasitic fragments in the Cross-Ambiguity-Function (CAF) to devaluate signal detection performance. A novel analysis of this mechanism and its impact is presented. A novel mSBZP-PCM-PCS algorithm is proposed, which does not degrade the CAF. Then, the algorithm is combined with SC bit transition removal schema and sequential search to construct an estimator for weak tiered signal acquisition. The performance of the method is demonstrated by analysis and computer simulation using Galileo E1C and GPS L1C-P signals.

An Accurate and Efficient Computation of Zeros and Poles of Transfer Function for Large Scale Circuits

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The zeros and poles of a circuit transfer function are computed solving a general eigenvalue problem, which could be transformed to a standard eigenvalue task to be solved by a suitably modified QR algorithm. Both reduction of the general eigenvalue problem to the standard form and the iterative procedures of the QR algorithm are very sensitive to the numerical precision of all calculations. The numerical accuracy is especially critical for two kinds of circuits: the microwave ones characterized by huge differences among magnitudes of the zeros and poles, and the large scale circuits, where the errors of the zeros and poles are increased by an extreme number of arithmetic operations. In the paper, an illustrative example of the reduction of the general eigenvalue problem and using the QR algorithm is shown first. After that, three circuits of various sizes are analyzed: simpler microwave low noise amplifier, larger power operational amplifier, and the most complex example with a 272 integrated operational amplifier. A meticulous comparison of obtained results shows that a usage of newly implemented 128-bit arithmetics in GNU Fortran or C compilers with partial pivoting can assure both efficient and enough accurate procedures for computing the zeros and poles.

Bias and variance of asymmetric double-sided two-way ranging

  • DOI: 10.1002/navi.321
  • Odkaz: https://doi.org/10.1002/navi.321
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The asymmetric double-sided two-way ranging (ADS–TWR) is a method of range estimation through precisely timestamped messages sent between two transceivers. In contrast to the symmetric double-sided two-way ranging (SDS–TWR), the ADS–TWR suppresses the errors induced by transceiver clock drifts even when the message reply delays are unequal. However, due to the nonlinearity of ADS–TWR estimator, its mean and variance cannot be evaluated in neither straightforward nor exact way. This article presents an analytical approach of evaluating an approximation of bias and variance of the range estimators and applies it on an exemplary set of parameters, which is typical for ultra-wide band (UWB) localization systems. Moreover, the obtained results are verified by a Monte–Carlo simulation. It will be proven that the ADS–TWR is safe to be used in most of the present applications and its precision is rather similar to SDS–TWR.

Hybrid Algorithm for Small Doppler Shifts Evaluation

  • DOI: 10.23919/IRS.2019.8768158
  • Odkaz: https://doi.org/10.23919/IRS.2019.8768158
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Improving performance of Doppler shift evaluation could be generally attempted by enhancement of hardware or software. The costly and inflexible nature of the former motivates us to gather as much as possible from the signal processing. The aim of our research has been to develop a real-time algorithm improving precision of Doppler shift evaluation for a standard, low-cost CW (continuous wave) Doppler radar. Emphasis has been put on close-to-zero Doppler shifts (i.e. low velocities), where standard algorithms usually do not provide accurate and reliable results. The proposed algorithm uses simple neural networks in order to provide the approximate estimate of the Doppler shift. According to their results, a proper processing method is chosen for the evaluation of the accurate Doppler shift value.

A Novel L-Probe Proximity Fed Patch Antenna with Parasitic Patch and Its Utilization in Antenna Arrays

  • DOI: 10.1088/1757-899X/321/1/012010
  • Odkaz: https://doi.org/10.1088/1757-899X/321/1/012010
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    An analysis of the L-probe fed patch antenna with an extraordinary parasitic patch is described. The element of the antenna is fed by the L-probe partially implemented in PCB. An excellent impedance matching is obtained (<-26 dB in the design frequency band 4.4-5 GHz). The radiation characteristics are also very good (gain > 10 dBi). For the numerical analyses, the Full Wave-CST Microwave Studio software was used in both frequency and time domains, and a very good agreement between the Time Domain Solver (TDS) and Frequency Domain Solver (FDS) was obtained. Real antenna samples have been created and measured as well as eight-element antenna arrays designed by the Dolph-Chebyshev method.

Chained wireless synchronization algorithm for UWB-TDOA positioning

  • DOI: 10.1109/PLANS.2018.8373376
  • Odkaz: https://doi.org/10.1109/PLANS.2018.8373376
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The Time Difference of Arrival is a popular method for UWB-based positioning, since it allows high position update rate even for multiple users. However, it requires the network infrastructure (anchors) to be synchronized, preferably with sub-nanosecond accuracy. Herein, an approach for synchronizing multiple anchors in a wireless, line-of-sight manner is described. This method is able to deal with UWB modules equipped with inexpensive drift-prone oscillators, as such impairments are estimated and compensated. By applying the proposed approach the influence of generally variable environment (e.g. temperature) on timing and positioning performance is reduced. Moreover, the presented algorithm is suitable for straightforward chaining of the line-of sight-segments in order to allow synchronization of distant anchors that cannot be synchronized with the master anchor directly.

Experimental evaluation of chained synchronization for UWB systems

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In the ultra-wide band (UWB) localization networks the time difference of arrival (TDoA) is often used. The TDoA method is advantageous in comparison with two-way ranging approach, however, requires the UWB infrastructure of the network to be synchronized to a sub-nanosecond level. The wireless synchronization is in favor due to practical reason, nonetheless its application is constrained by the need of line-of-sight between the synchronized nodes. This paper focuses on an experimental evaluation of a Kalman-filter-based chained synchronization algorithm, which allows synchronization of a distant, directly unreachable UWB nodes through multiple nodes and the respective line-of-sight path segments.

Joint Estimator for Acquisition of GNSS Primary and Secondary Code with Pre-correlation Coherent Accumulation

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Objective of this contribution is the acquisition algorithm for modern GNSS signals containing secondary codes. This algorithm is usable for a hardware based GNSS signal acquisition unit using the parallel code search (PCS) algorithm. The contribution deals with standard post-correlation methods and focuses on a comparison of methods based on a pre-correlation accumulation of the signal by the Pre-correlation Coherent Accumulation principle (PCA). The aim is a comparison of properties of different types of used zero-padding methods in both pre and post correlation approaches. An extension of a coherent time in front of a PCS-FFT algorithm based unit by help of a pre-correlation processing could considerably reduce a required minimal latency of FFT blocks. A latency time equal to one period of primary code for the post-correlation combining is replaced for a proposed algorithm to a much longer time equal to a period of the secondary code.

Novel Method for Noise Figure Measurement of Antenna Low Noise Amplifiers Optimized for a Trade-Off Between Gain and Noise Properties

  • DOI: 10.1109/APCAP.2018.8538100
  • Odkaz: https://doi.org/10.1109/APCAP.2018.8538100
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The best properties of antenna low noise preamplifiers can be achieved by the multi-objective optimization which generates a trade-off between the transducer power gain and noise figure in the form of Pareto front. However, as the resultant circuit designed in this way is not fully matched at the output, measuring the amplifier - unmatched neither to gain nor to noise figure - is quite difficult, especially in the case of very low noise figures. In this paper, a more accurate two-stage measurement method is presented, where both calibration and measurement stages contain improvements to end the device with standard impedances and increase needed overall measurement sensitivity.

Pre- and Post-Correlation Method for Acquisition of New GNSS Signals with Secondary Code

  • DOI: 10.1109/PLANS.2018.8373535
  • Odkaz: https://doi.org/10.1109/PLANS.2018.8373535
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Correlation of GNSS signals that is implemented into a block processing by help of a FFT allows using and evolving of methods that has never been used before in a traditional continual processing. Our contribution focuses on utilization of a block pre-correlation processing for an acquisition of modern GNSS signals. This method combines the parallel in code search (PCS) algorithm with the Pre-Correlation Averaging (PCA) method for an acquisition of a secondary code of GNSS signals. The PCA method averages samples of consecutives signal periods and averages them together period-by-period coherently to allow using a longer coherent time without additional costs in correlation stage and without boost of the FFT unit size.

Proposal of a Memory Architecture for Pre and Post-Correlation coherent Processing of GNSS Signal with SoC based Acquisition Uni

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This contribution describes an architecture of additional system of memories for an existing GNSS (Global Navigation Satellite Systems) signal acquisition unit in frequency domain. The unit is designed for an FPGA-based HW receiver and has three 4K FFT blocks. The receiver is based on the System on Chip (SoC) Xilinx ZYNQ platform. The proposed additional memories are used as accumulators of complex signals samples and are placed in front or after the acquisition unit. They enable to process GNSS signals of different navigation systems more effectively with limited resources

The DVB–T–Based Positioning System and Single Frequency Network Offset Estimation

  • DOI: 10.13164/re.2018.1155
  • Odkaz: https://doi.org/10.13164/re.2018.1155
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    As position information becomes more and more important in many fields of technology it is advantageous to recognize it in scenarios where satellite-based systems fail. Such a case is the scenario inside buildings where attenuation of a signal is too high making it impossible to receive despite the availability of terrestrial services. A positioning system based on terrestrial broadcasting is presented in this paper. The aim is to create an automatic receiver enabling a multi–sensor positioning system to be built and resulting in increased availability and reliability of position information. This paper introduces a method that demonstrates how to design a signal detector capable of operating in a multipath scenario. Finally, the most restrictive problem of the positioning system is the unknown time offset setting of individual emitters that render this system useless. A solution to this problem is proposed and tested in a real scenario. The innovative methods and algorithms presented in this paper show, for the first time, howto automatically evaluate position using digital video broadcasting. The result of an experiment with a real digital video broadcasting network is presented.

A new assessment method of pHEMT models by comparing relative errors of drain current and its derivatives up to the third order

  • DOI: 10.1088/1757-899X/198/1/012004
  • Odkaz: https://doi.org/10.1088/1757-899X/198/1/012004
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Nowadays, there exist relatively precise pHEMT models available for computer-aided design, and they are frequently compared to each other. However, such comparisons are mostly based on absolute errors of drain-current equations and their derivatives. In the paper, a novel method is suggested based on relative root-mean-square errors of both drain current and its derivatives up to the third order. Moreover, the relative errors are subsequently relativized to the best model in each category to further clarify obtained accuracies of both drain current and its derivatives. Furthermore, one our older and two newly suggested models are also included in comparison with the traditionally precise Ahmed, TOM-2 and Materka ones. The assessment is performed using measured characteristics of a pHEMT operating up to 110 GHz. Finally, a usability of the proposed models including the higher-order derivatives is illustrated using s-parameters analysis and measurement at more operating points as well as computation and measurement of IP3 points of a low-noise amplifier of a multi-constellation satellite navigation receiver with ATF-54143 pHEMT.

Acquisition of Modern GNSS Signals in SoC ZYNQ with its Limited Computational Resources in Frequency Domain

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The objective of this contribution is a design of optimal algorithms for an universal GNSS acquisition unit. The unit is designed for a FPGA-based HW receiver and is implemented in frequency domain with three 4K FFT blocks. The unit is able to acquire usual civil signals (GPS C/A, BeiDou B1, IRNSS L5/S-band, and GLONASS L1OF) directly and to acquire the Galileo E1 longer code signal with proposed improved algorithm of the partial correlation. Pre- and mainly post-correlation methods are analyzed and selected with respect to implementation on the target System on Chip (SoC) Xilinx ZYNQ platform with limited computing resources.

Analysis of L-Probe Proximity Fed Patch Antenna With Parasitic Patch

  • DOI: 10.23919/RADIO.2017.8242219
  • Odkaz: https://doi.org/10.23919/RADIO.2017.8242219
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper, an analysis of the Fat Patch Antenna with the extraordinary parasitic patch is described. For the numerical simulations, the Full Wave-CST Microwave Studio software is used. The element of the antenna is fed by the L-probe partially implemented in PCB. An excellent impedance matching is obtained (< 26 dB in the design frequency band 4.4-5 GHz). The radiation characteristics are also very good (gain > 10 dBi). A very good agreement between the Time Domain Solver (TS) and Frequency Domain Solver (FS) has also been obtained. Real antenna samples have been created and measured as well as eight-element antenna arrays designed by Dolph-Chebyshev method.

Methods and Hardware achitecture for Multi-constellation GNSS signal acqusition unit in frequency domain

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The objective of this contribution is a design of universal GNSS acquisition unit for an FPGA-based HW receiver, which is able of direct acquisition of usual civil signals (GPS C/A, BeiDou B1, IRNSS L5/S-band, and GLONASS L1OF). Due to high complexity of calculation and requirements for latency, processing in frequency domain with parallel search in code is adopted. Optimal processing methods even for the long codes of Galileo E1 or future GPS L1C signals are analyzed. For each block of the acquisition unit, a method is selected with respect to implementation on the target System on Chip (SoC) Xilinx ZYNQ platform. The unit is intended as a HW acquisition accelerator with a minimal SW handling requirements for the developed receiver.

A new assessment of pHEMT models by comparing relative errors of drain current and its derivatives up to the third order

  • DOI: 10.1109/RADIO.2016.7772016
  • Odkaz: https://doi.org/10.1109/RADIO.2016.7772016
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    At present, there are relatively more precise pHEMT models available for computer-aided design, and they are frequently compared to each other. However, such comparisons are mostly based on absolute errors of drain-current equations and their derivatives. In the paper, a novel method is suggested based on relative root-mean-square errors of both drain current and its derivatives up to the third order. Moreover, the relative errors are then relativized to the best model in each category to further clarify obtained accuracies of the drain current and its derivatives. Furthermore, one our older and two newly suggested models are also included in the comparison with the traditionally accurate Ahmed, TOM2 and Materka ones. The assessment is performed using measured characteristics of a 110 GHz pHEMT. Finally, a usability of the models of the higher-order derivatives is illustrated using an IP3 computation/measurement of a multi-constellation receiver for a satellite navigation with ATF-54143.

A New Criterion for Stability Assessment of the Microwave pHEMT-based Low-Noise Amplifiers

  • DOI: 10.1109/IMFEDK.2016.7521697
  • Odkaz: https://doi.org/10.1109/IMFEDK.2016.7521697
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    At present, the foremost low-noise amplifiers are based on usage of the pseudomorphic high-electron-mobility transistors (pHEMTs). However, in many cases, the amplifiers are often constructed at the limits of absolute stability or even in the region of potential instability because only such solutions give requested circuit properties as a trade-off between the transducer power gain and noise figure. The stability properties are mostly checked by the classical criteria such as the Rollett conditions, mu-factor etc. In the paper, a novel additional very efficient criterion is proposed, finding the most critical couple of poles and evaluating the ratio of imaginary and real part. The efficiency of the method is demonstrated on a low-noise antenna preamplifier for a multi-constellation satellite-navigation receiver based on an ATF-54143 pHEMT.

Analysis, Modeling, and Mitigation of Cross-Rate Interference in eLoran

  • DOI: 10.1002/navi.142
  • Odkaz: https://doi.org/10.1002/navi.142
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The General Lighthouse Authorities of the UK and Ireland (GLA) have selected eLoran as the most cost-effective way of complementing GNSS to provide resilient positioning, navigation, and timing within their waters. Achieving adequate eLoran coverage over the GLA service area will require a number of new transmitting stations to be installed. Due to the nature of eLoran transmissions, new stations can contribute as sources of interference which is often referred to as Cross-Rate Interference (CRI). This paper investigates the impact of CRI on the positioning accuracy of eLoran and explores mitigation methods. Analytical models of the pseudorange and positioning error due to CRI are presented and validated, and applications to coverage prediction and optimal eLoran Group Repetition Interval (GRI) selection are demonstrated. Results show that the CRI-induced errors can be substantially reduced through the judicious choice of GRIs and the use of state-of-the-art eLoran signal processing techniques.

Position Estimate using Radio Signals from Terrestrial Sources

  • DOI: 10.1109/PLANS.2016.7479775
  • Odkaz: https://doi.org/10.1109/PLANS.2016.7479775
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The satellite navigation is supposed to be used in applications that need coordinates generally. However we can meet a plenty of satellite signal reception problems in a real environment, often called as difficult conditions. The difficult conditions hinder reliable positioning with required accuracy, often in applications that are important for saving or securing the safety of human lives (work of rescue teams, protection of people in large warehouses, safety of lone forest workers, etc.). The main reason for this is the weakness of the received satellite signals. In addition to that, the weak signals are also highly vulnerable by interference, spoofing or jamming, even with the low-power and often generated by low-cost devices. In spite of this, radio systems complementing and making the backup of the satellite positioning are searched. There are terrestrial radio systems using high-power signals with properties which are suitable for the positioning purposes. The most important property in conjunction with the sufficiently high power is a very sharp and possibly unambiguous correlation function. Besides the signals of systems used primarily for the navigation (such as eLORAN, e.g.) signals of some systems primarily dedicated to communication have the acceptable properties mentioned above. They are usually called Signals of Opportunity. As an example let us mention signals of the DVB-T, LTE, Wi-Fi, etc. In the field of indoor navigation signal strength fingerprinting is frequently used. However, for much larger open areas this approach is not the best one, because it requires a kind of a site survey to be done. In case of outdoor applications, the use of different principles has to be considered. The methods based on signal power and angles of arrival measurements have been found unsuitable because they may be misleading even in a lightly obstructed area. ...

Analysis, Modelling and Mitigation of Cross-Rate Interference in eLoran

  • Autoři: Šafář, J., Williams, P., Grant, A., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of the 2015 International Technical Meeting of The Institute of Navigation. Washington: Institute of Navigation, 2015. p. 1-26. ISBN 978-1-5108-0043-4.
  • Rok: 2015
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The General Lighthouse Authorities of the UK and Ireland (GLA) have selected eLoran as the most cost-effective way of complementing GNSS to provide resilient Positioning, Navigation and Timing (PNT) within their waters. The GLA has established eLoran Initial Operational Capability (IOC) in the seven busiest UK ports and port approaches along the east coast. It is anticipated that the GLA eLoran service will expand to cover all of the waters around the United Kingdom and Ireland, including the English Channel as part of the system's Final Operational Capability (FOC). This will require a number of new transmitting stations to be installed, which must work with those already in situ. Recent developments in new technology transmitters have created the potential for cost-effective eLoran signal provision. However, due to the nature of eLoran transmissions new stations can contribute as sources of interference which is often referred to as Cross-Rate Interference (CRI), and, if left uncompensated, is one of the major sources of measurement error. This paper reports on some of the findings of a PhD study which investigated the impact of CRI on the positioning accuracy of eLoran and explored ways of mitigating this impact through modern receiver signal processing and the judicious choice of the signal Group Repetition Intervals (GRI).

Comparing the Steady-State Procedures Based on Epsilon-Algorithm and Sensitivity Analysis

  • DOI: 10.1109/ICECS.2015.7440388
  • Odkaz: https://doi.org/10.1109/ICECS.2015.7440388
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Although many programs have built-in various methods for finding the steady state nowadays, their actual implementations are often quite unsatisfactory regarding algorithm efficiency and reliability. We improved and checked procedures built on both epsilon-algorithm and sensitivity analysis in time domain. First of all, it was clearly demonstrated that increasing demands on the overall numerical accuracy do not lead to an excessive number of necessary integration steps and therefore LU factorizations correspondingly. This feature is especially significant for the suggested procedure based on the epsilon-algorithm. Furthermore, the practical experiments confirmed that a proposed arrangement of the extrapolation method is greatly insensitive to its order, which is even more important because a program user is unable to estimate the appropriate order for complicated circuits well. The properties of the methods are demonstrated using rectifier, C-class amplifier, and LNA for which exceptional attention was given to checking the insensitivity of the extrapolation to its order.

Experiments with Reception of IRNSS Satellite Navigation Signals in the S and C Frequency Bands

  • DOI: 10.1201/b18513-37
  • Odkaz: https://doi.org/10.1201/b18513-37
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The satellite navigation is typically considered as the processing of satellite radio signals in the L frequency band (1.151 to 1.214, 1.215.6 to 1.350, and 1.559 to 1.617 GHz). However, in the process of the Galileo signals design the S (2483.5 to 2500 MHz) and C (5010 to 5030 MHz) bands have been taken into account, too. The S band was allocated to the Radiodetermination Satellite Service by the International Telecommunication Union (ITU) at the World Radio Conference 2000 (WRC 2000), whereas the C band signals were intensively studied in the period 1998 – 2004. Both of the bands were associated with the plans for the Galileo but have not been applied yet. A part of the S band has been lately (since summer 2013) used for the Open Service of the Regional Indian Radio Navigation Satellite System (IRNSS). The two bands have both specific advantages and deficiencies which we will analyse in our contribution. We will refer also to our experiments with the S band IRNSS signals reception and their use for determination of ionosphere and troposphere properties.

Multi-Objective Optimization of a Low-Noise Antenna Amplifier for Multi-Constellation Satellite-Navigation Receivers

  • DOI: 10.1109/SOCC.2015.7406919
  • Odkaz: https://doi.org/10.1109/SOCC.2015.7406919
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Although the major parts of function blocks for the satellite navigation receivers are fully integrated in a CMOS chip in most cases, it is convenient to create an antenna preamplifier as a separate circuit based on a low-noise pHEMT. Such an RF front end can be strongly optimized to attain a trade-off between the noise figure and transducer power gain. Furthermore, as all the principal navigation systems (GPS, GLONASS, Galileo, and Compass) work in similar frequency band (roughly from 1.1 to 1.7 GHz), it is reasonable to create this low-noise preamplifier for all of them. In the paper, a sophisticated method of the amplifier design is suggested based on multi-objective optimization. First, an extraction of pHEMT model parameters was performed, including comparisons among several models. The extraction was carried out by our original three-step robust identification procedure based on a combination of meta-heuristic and direct optimization methods. Second, a substantial improvement of a standard method for the multi-objective optimization is outlined. Third, the equations of passive elements of the circuit (including transmission lines and T splitters) were carefully defined using frequency dispersion of their parameters as Q, ESR, etc. Fourth, an optimal selection of the amplifier operating point and essential passive elements was performed using the previously improved goal attainment method. Finally, the s-parameters and noise figure of the proposed preamplifier were measured, and the third-order intermodulation products were also checked.

Precise Characterization and Multiobjective Optimization of Low Noise Amplifiers

  • DOI: 10.13164/re.2015.0670
  • Odkaz: https://doi.org/10.13164/re.2015.0670
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Although practically all function blocks of the satellite navigation receivers are realized using the CMOS digital integrated circuits, it is appropriate to create a separate low noise antenna preamplifier based on a low noise pHEMT. Such an RF front end can be strongly optimized to attain a suitable tradeoff between the noise figure and transducer power gain. Further, as all the four principal navigation systems (GPS, GLONASS, Galileo, and COMPASS) work in similar frequency bands (roughly from 1.1 to 1.7 GHz), it is reasonable to create the low noise preamplifier for all of them. In the paper, a sophisticated method of the amplifier design is suggested based on multiobjective optimization. A substantial improvement of a standard optimization method is also outlined to satisfy a uniform coverage of Pareto front. Moreover, for enhancing efficiency of many times repeated solutions of large linear systems during the optimization, a new modification of the Markowitz criterion is suggested compatible with fast modes of the LU factorization. Extraordinary attention was also given to the accuracy of modeling. First, an extraction of pHEMT model parameters was performed including its noise part, and several models were compared. The extraction was carried out by an original identification procedure based on a combination of metaheuristic and direct methods. Second, the equations of the passive elements (including transmission lines and T-splitters) were carefully defined using frequency dispersion of their parameters as Q, ESR, etc. Third, an optimal selection of the operating point and essential passive elements was performed using the improved optimization method. Finally, the s-parameters and noise figure of the amplifier were measured, and stability and third-order intermodulation products were also checked.

Multiobjective Optimization of Input Low Noise Amplifier for Common GPS/Galileo/GLONASS/Compass Satellite Navigation System Receiver

  • DOI: 10.1109/ISOCC.2014.7087575
  • Odkaz: https://doi.org/10.1109/ISOCC.2014.7087575
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    As all the four main navigation systems (GPS, Galileo, GLONASS, and Compass) work in similar frequency bands, it is reasonable to create a common input low noise amplifier for all of them. Although the whole chip including a lot of correlators and other digital circuits is quite complicated, a common low noise antenna preamplifier operating at the frequencies from 1.1 to 1.7 GHz could be quite simple and efficient. We have proposed finding a compromise between the amplifier’s amplification and noise figure under several natural constrains by multiobjective optimization. Moreover, we have utilized our enhancement of known optimization algorithm (the goal attainment method) to improve its efficiency, which led to finding a very good design tradeoff for the amplifier.

Using the Sensitivity Analysis of the Noise Spectral Density and the Sensitivity Analysis of the Noise Figure for Practical Circuit Design

  • DOI: 10.1109/ISCAS.2014.6865475
  • Odkaz: https://doi.org/10.1109/ISCAS.2014.6865475
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Although the sensitivity analysis is implemented in contemporary software tools for computer-aided design, kinds of available sensitivities are limited. For example, Spice or Micro-Cap calculate DC or small-signal AC sensitivities, and SpectreRF contains a periodic noise analysis or a parametric sensitivity analysis that can be efficiently used for determining the phase noise. In this paper, some novel types of the noise sensitivity analysis are described, which are not implemented in the usually applied circuit simulators. First, a procedure for determining the sensitivities of the noise figure was suggested. Second, an improvement of the algorithm for computing the noise figure was described, which incorporates circuit matching and eliminates necessary subtraction of the output noise generated by the load resistance at each frequency. Third, a new formula was derived for a computation of the sensitivities of the noise figure. The sensitivity analysis of the noise spectral density is demonstrated by means of an analytically solved example. The application of the sensitivity analysis of the noise figure for improving the noise properties of a microwave integrated circuit is described in a detailed way as well. Finally, using a sophisticated multi-objective optimization is suggested for a better selection of the operating point instead of classical circuit matching. This method was utilized for a practical design of an antenna preamplifier for a GPS/Galileo/GLONASS/Compass receiver.

Accuracy Performance of eLoran Receivers under Cross-Rate Interference Conditions

  • DOI: 10.2478/v10367-012-0011-y
  • Odkaz: https://doi.org/10.2478/v10367-012-0011-y
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We examine the impact of CRI on the position accuracy performance of eLoran receivers. The theoretical results are compared to those obtained from measurements made on a commercially available receiver.

Distributed Extended Kalman Filter for Position, Velocity, Time Estimation in Satellite Navigation Receivers

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Common techniques for position-velocity-time estimation in satellite navigation, iterative least squares and the extended Kalman filter, involve matrix operations. The matrix inversion and inclusion of a matrix library pose requirements on a computational power and operating platform of the navigation processor. In this paper, we introduce a novel distributed algorithm suitable for implementation in simple parallel processing units each for a tracked satellite. Such a unit performs only scalar sum, subtraction, multiplication, and division. The algorithm can be efficiently implemented in hardware logic. Given the fast position-velocitytime estimator, frequent estimates can foster dynamic performance of a vector tracking receiver. The algorithm has been designed from a factor graph representing the extended Kalman filter by splitting vector nodes into scalar ones resulting in a cyclic graph with few iterations needed. Monte Carlo simulations have been conducted to investigate convergence and accuracy. Simulation case studies for a vector tracking architecture and experimental measurements with a real-time software receiver developed at CTU in Prague were conducted. The algorithm offers compromises in stability, accuracy, and complexity depending on the number of iterations. In scenarios with a large number of tracked satellites, it can outperform the traditional methods at low complexity.

Novinky v družicových navigačních systémech

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Příspěvek shrnuje aktuální novinky v oblasti družicové navigace, přehled stávajících a plánovaných systémů a nejdůležitějších změn v jejich službách a struktuře signálů.

Novinky v družicových navigačních systémech

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Popis čtyř hlavních systémů družicové navigace (GPS, GLONASS, Galileo, Compass). Použité kmitočty a kódy.

Novinky v družicových navigačních systémech

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Popisuje čtyři systémy: GPS, GLONASS, Galileo a Beidou. Zabývá se především strukturou signálů pro neautorizované uživatele.

Study of the RF Front-end of the Multi-Constellation GNSS Receiver

  • DOI: 10.1201/b14961-35
  • Odkaz: https://doi.org/10.1201/b14961-35
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper presents analysis of the requirements on the RF Front-end of the Multi-Constellation GNSS Receiver. One of the main problems of the multi-constellation GNSS receiver is the amplifying ans splitting of signals of partial systems working in different bands.The paper studies a variety of possibilities of the design of the multi-constellation receiver frontend from the noise figure and jamming resistance point of view.

Accuracy Performance of eLoran Receivers under Cross-Rate Interference Conditions

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We examine the impact of CRI on the position accuracy performance of eLoran receivers. The theoretical results are compared to those obtained from measurements made on a commercially available receiver.

Dual-frequency Tracking of Compass Signals: Compass Implementation to the Witch Navigator Receiver

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper describes the implementation of the Compass signal processing for the Witch Navigator receiver - an experimental GNSS software receiver for research and education purposes which has been developing at CTU in Prague. The description is shown in comparison with the implementation of the legacy signal processing: GPS L1 C/A and GLONASS L1. It is practically verified that the Compass signal has great compatibility with GPS/GLONASS signals, which results in simplification of multi-system receiver. The implemented Compass receiver can process signals in B1 (E2) and B2 (E5b) bands simultaneously. Due to rapid deployment of the Compass constellation it is now possible to perform real-time and dual-frequency measurement in geographical location of the Czech Republic, Prague. All three satellite types are visible in Prague: GEO, IGSO and MEO. Paper shows measurement results and is focused on signal characteristics and their quality.

Economic Galileo E5 Receiver

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The Galileo system introduces an extremely wideband civil E5 signal for high precision navigation. The structure of the receiver for the E5 signal is complicated due to the signal complexity and the large bandwidth. It is possible to process the whole E5 signal or process separately E5a and E5b parts combining obtained results afterwards (we call here such method as piece-wise processing). The second procedure has three times worse standard deviation of the pseudorange then first one. The main goal of the paper is to present a design of an E5 receiver which we will call the economic E5 receiver (ecoE5). It is built from jointly controlled correlators for the processing of the E5a and E5b signals which are parts of the E5 signal. Control of these partial E5a and E5b correlators is realized by only one delay and one phase lock loops. The performance, i.e. the pseudorange noise and multipath errors, of the receiver equipped with the ecoE5, is only slightly worse (the standard deviation of the pseudorange noise is 10 - 20% larger) than the performance of the optimal E5 receiver and it is much better than the performance of the receiver combining the piecewise (E5a and E5b) measurements. The ecoE5 receiver hardware demands are about one quarter of the hardware demands of the classical E5 receiver.

GNSS signal processing in GPU

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In the paper, the study of the applicability of the GPU approach in GNSS signal acquisition is studied. Two methods, PCSS and DBZP, have been investigated with discussed implementation in C and CUDA languages.

Universality and Realistic Extensions to the Semi-Analytic Simulation Principle in GNSS Signal Processing

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Semi-analytic simulation principle in GNSS signal processing bypasses the bit-true operations at high sampling frequency. Instead, signals at the output branches of the integrate&dump blocks are successfully modeled, thus making extensive Monte Carlo simulations feasible. Methods for simulations of code and carrier tracking loops with BPSK, BOC signals have been introduced in the literature. Matlab toolboxes were designed and published. In this paper, we further extend the applicability of the approach. Firstly, we describe any GNSS signal as a special instance of linear multi-dimensional modulation. Thereby, we state universal framework for classification of differently modulated signals. Using such description, we derive the semi-analytic models generally. Secondly, we extend the model for realistic scenarios including delay in the feed back, slowly fading multipath effects, finite bandwidth, phase noise, and a combination of these. Finally, a discussion on connection of this semi-analytic model and position-velocity-time estimator is delivered, as well as comparison of theoretical and simulated characteristics, produced by a prototype simulator developed at CTU in Prague.

Assessing the Limits of eLoran Positioning Accuracy

  • Autoři: Šafář, J., prof. Ing. František Vejražka, CSc., Williams, P.
  • Publikace: Navigational Systems and Simulators, Marine Navigation and Safety of Sea Transportation. Leiden: CRC Press/Balkema, 2011, pp. 55-63. ISBN 978-0-415-69113-0.
  • Rok: 2011
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Enhanced Loran (eLoran) is the latest in the longstanding and proven series of low frequency, LOng-RAnge Navigation systems. eLoran evolved from Loran-C in response to the 2001 Volpe Report on GPS vulnerability. The Czech Technical University in Prague (CTU) participates in the eLoran research activities coordinated by the General Lighthouse Authorities of the United Kingdom and Ireland (GLAs). In our work we have focused on questions that arise when considering introducing new eLoran stations into an existing network. In particular, this paper explores the issue of Cross-Rate Interference (CRI) among eLoran transmissions and possible ways of its mitigation at the receiver end.

Assessing the Limits of eLoran Positioning Accuracy

  • Autoři: Šafář, J., prof. Ing. František Vejražka, CSc., Williams, P.
  • Publikace: The International Journal on Marine Navigation and Safety of Sea Transportation. 2011, 5(1), 93-101. ISSN 2083-6473.
  • Rok: 2011
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Enhanced Loran (eLoran) is the latest in the longstanding and proven series of low frequency, LOng-RAnge Navigation systems. eLoran evolved from Loran-C in response to the 2001 Volpe Report on GPS vulnerability. The next generation of the Loran systems, eLoran, improves upon Loran-C through enhancements in equipment, transmitted signal, and operating procedures. The improvements allow eLoran to provide better performance and additional services when compared to Loran-C, and enable eLoran to serve as a backup to satellite navigation in many important applications. The Czech Technical University in Prague (CTU) participates in the eLoran research activities coordinated by the General Lighthouse Authorities of the United Kingdom and Ireland (GLAs). In our work we have focused on questions that arise when considering introducing new eLoran stations into an existing network. In particular, this paper explores the issue of Cross-Rate Interference (CRI) among eLoran transmissions and possible ways of its mitigation at the receiver end. An eLoran receiver performance model is presented and validated using an experimental eLoran signal simulator developed by a joint effort of CTU and GLAs. The resulting model is used to evaluate the achievable positioning accuracy of eLoran over the British Isles.

Galileo - systém družicové navigace

  • Autoři: prof. Ing. František Vejražka, CSc., Kačmařík, P.
  • Publikace: Perspektivy elektroniky 2011. Rožnov pod Radhoštěm: Střední škola informatiky, elektrotechniky a řemesel, 2011. pp. 89-93. ISBN 978-80-254-9992-4.
  • Rok: 2011
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    V příspěvku se stručně zabýváme stavem družicového navigačního systému Galileo, použitými kmitočty a modulacemi a důvody pro jejich použití. Na základě našich experimentů s příjmem družic GIOVE se pokoušíme ukázat, proč by mělo Galileo dosahovat velké přesnosti určení polohy.

Interoperable GPS, GLONASS and Galileo Software Receiver

  • DOI: 10.1109/MAES.2011.5763340
  • Odkaz: https://doi.org/10.1109/MAES.2011.5763340
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The new and modernized GNSS navigation systems will provide various navigation services and signals for civil user. The system operators work on basic interoperability agreements which simplify multi-system navigation receiver architecture and reduce its cost. The most current GNSS signals can be processed by one or several classical E-L correlators with a look up table PRN generator of a length of 10,230 chips. Most signals are processed optimally, but for some signals, like Galileo E1b and E1c or GPS L1C, this signal processor does not utilize all signal components and properties. The proposed E-L correlator was implemented to the FPGA of the experimental software GNSS receiver and was tested on the Galileo E1b, E1c, and E5a signals. The target multi-system GNSS receiver architecture based on an ExpressCard peripheral card for the standard PC computer or notebook is described herein. Up to one hundred universal correlators and signal snapshot capture unit ...

Interoperable GPS, GLONASS and GALILEO Software Receiver

  • DOI: 10.1134/S2075108711020040
  • Odkaz: https://doi.org/10.1134/S2075108711020040
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The new and modernized GNSS navigation systems will provide various navigation services and signals for civil user. The system operators work on basic interoperability agreements which simplify multisystem navigation receiver architecture and reduce its cost. The most current GNSS signals of GPS, GLONASS and GALILEO can be processed by one or several classical EL correlators with a look up table PRN generator of length 10230 chips. Most signals are processed optimally, but for some signals, like Galileo E1b and E1c or GPS L1C, this signal processor does not utilize all signal components and properties. The proposed EL correlator was implemented to the FPGA of the experimental software GNSS receiver and was tested on the GALILEO E1b, E1c and E5a signals. The target multisystem GNSS receiver architecture based on an ExpressCard peripheral card for the standard PC computer or notebook is described in the paper. Up to hundred universal correlators and also signal snapshot capture unit..

Novinky v družicové navigaci

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Příspěvek pojednává o novinkách z oblasti družicových navigačních systémů. Analyzuje důvody zlepšení základních parametrů navigace. Příspěvek dále prezentuje výsledky zpracování signálu experimentální družice GIOVE-A.

Reduced-complexity GNSS Software Simulator Based on Correlator Output Signal Modeling

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This article presents an algorithm for reducing complexity of GNSS tracking simulators. The existing simulators, known as bit true, are solely based on generation and processing of IF samples. The introduced simulator generates the signals at the output branches of the correlators, hence lowers the sampling rate from tens of Megahertz down to units of kilohertz. The user further does not need to enter the spreading codes, but their correlation functions. This approach limits the algorithms to be tested under high dynamics, fadings and interference. However, fast initial design can be carried out hereby. A prototype simulator has been developed and tested under the Matlab environment.

The Implementation of the Dual Frequency GLONASS Receiver to the Witch Navigator

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper discusses the implementation of the dual frequency GLONASS receiver to the Witch Navigator software receiver. The Witch Navigator is an open source software receiver designed for study and research purposes. We review the Witch Navigator software and hardware concepts as well as their mutual interactions. Focus is placed on the GLONASS specific code with the utilization of either frequency. Finally, results of the so far implemented software blocks are presented.

The Witch Navigator -- A Software GNSS Receiver Built on Real-Time Linux

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The Witch Navigator (WNav) is an open source project of GNSS (Global Navigation Satellite System) receiver whose hardware is implemented as an ExpressCard hosted in PC with Linux OS. The paper describes the whole conception of WNav with focus on the kernel part (device driver) and the real-time user space process, provides information about the processes synchronization and presents the achieved performance. The first obvious milestone is to develop the fully functional GPS L1 C/A receiver which justifies the selected conception. The achieved results and experience with this legacy signal are presented in the paper, as well.

Witch Navigator - a Low Cost Software Receiver for Education and Research

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The Witch Navigator is a low cost software receiver developed at the Czech Technical University for education and research purposes. The receiver is designed universally for various missions from simple single frequency GPS L1 C/A receivers to complex multi-GNSS-system, multi-frequency and multi-antenna receiver. The Witch Navigator receiver is designed as an ExpessCard periphery for a notebook or a PC. The cards can be mutually interconnected to the large system. The Witch Navigator is equipped with a powerful FPGA capable to run GNSS correlators (traditional receiver concept) or to send GNSS signal samples to the PC for entire processing.

Witch Navigator -- a software GNSS receiver for education and research

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper introduces the Witch Navigator, which is an ExpressCard form factor software GNSS receiver for a notebook or a personal computer, developed for educational and research purposes. The signal processing runs on a FPGA and a PC processor, the mutual communication is realized via a PCI Express bus. The receiver is equipped with two reconfigurable front ends. The complex multi-antenna, multi-frequency and multi-constellation GNSS system can be built by interconnecting several receiver cards by a special connector.

Galileo AltBOC E5 Signal Characteristics for Optimal Tracking Algorithms

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with an optimal processing of a Galileo E5 signal. A proposed correlator structure was developed on a base of a deep study of an E5 signal cross correlation function. Due to the non linearity of the E5 AltBOC modulation the proposed correlator calculates the cross correlation function between a received signal and a signal replica for all possible hypotheses of the navigation message bits. A correct peak tracking verification is realized by implementation of a single side band correlator, which also serves for course signal acquisition and secondary ranging code synchronization. The signal processing was verified on the Galileo Giove A and Giove B satellites with very positive preliminary results.

Interoperable GPS, GLONASS and Galileo Software Receiver

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Our paper deals with the interoperable software receiver concept developed at the Czech Technical University.

Low Complex Interoperable GNSS Signal Processor and its Performance

  • DOI: 10.1109/PLANS.2010.5507229
  • Odkaz: https://doi.org/10.1109/PLANS.2010.5507229
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The recent development of the GNSS systems and international cooperation resulted in important technical problems of the GNSS systems which are an interoperability and compatibility. In the interoperable receivers the most expensive parts - front ends - can be shared for signals reception of different systems. The unification of the signal processor is also possible with some small performance deterioration but the hardware complexity reduction is considerable. The paper analyses applicability of a classical E-L correlator for processing of various GNSS signals and compare its performance with optimal method. The low complex interoperable processor of software receiver based on a FPGA for the GPS, Galileo and GLONASS systems is proposed. The results of testing on the Galileo E1 and E5 signals are presented. The last part of the paper proposes architecture of a low cost multi system GNSS receiver based on mass market components.

Programmnyj GPS/GLONASS/GALILEO priemnik

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Opisyvaetsâ arhitektura mul´tisistemnogo priemnika GNSS, postroennogo na baze periferijnoj platy ExpressCard dlâ standartnogo personal´nogo komp´ûtera ili noutbuka. V PPVM priemnika realizuetsâ do sta universal´nyh korrelâtorov i vypolnâetsâ zahvat i cifrovaâ obrabotka signalov. Privoditsâ obzor harakteristik nastoâŝih i perspektivnyh signalov sistem GPS, GLONASS i GALILEO dlâ graždanskih potrebitelej. Predlagaetsâ prostaâ struktura E-L-korrelâtora GNSS i opisyvaûtsâ vozmožnosti ego ispol´zovaniâ dlâ obrabotki časti signalov GNSS. Privodâtsâ rezul´taty ispytanij korrelâtora s signalami E1 i E5a sistemy GALILEO, vyvody.

The Witch Navigator - A Low Cost GNSS Software Receiver for Advanced Processing Techniques

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The developement of advanced GNSS signal processing algorithms such as multi-constellation, multi-frequency and multi-antenna navigation requires an easily reprogrammable software defined radio solution. Various receiver architectures for this purpose have been introduced. RF front-end with FPGA universal correlators on ExpressCard connected directly to PC was selected and manufactured. Such a~unique hardware combination provides the GNSS researchers and engineers with a~great convenience of writing the signal processing algorithms including tracking, acquisition and positioning in the Linux application programming interface and enables them to reconfigure the RF front-end easily by the PC program. With more of these ExpressCards connected to the PC, the number of the RF channels, correlators or antennas can be increased to further boost the computational power. This paper reveals the implementation aspects of the receiver, named the Witch Navigator, and~gives the key test results.

Cross-Rate Interference and Implications for Core eLoran Service Provision

  • Autoři: Šafář, J., Williams, P., Basker, S., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of ILA 38th Annual Convention and Technical Symposium. Santa Barbara, CA: International Loran Association, 2009. pp. 1-16.
  • Rok: 2009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    At the NAV08/ILA37 conference we presented a set of Matlab tools, which implement a GRI selection technique based on methods sanctioned by the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) for the establishment of new Loran-C chains. We also extended the techniques by developing a number of updates that take into account the modernization of Loran-C to the eLoran standard. In this new paper we continue our investigations and take a closer look at the problem of CRI. We quantify positioning errors introduced by unmitigated CRI. We then demonstrate how CRI can be mitigated in an eLoran receiver by blanking the interfering pulses and we show the impact of the attendant blanking loss on the accuracy performance of eLoran core service provision.

Galileo AltBOC E5 Signal Characteristics for Optimal Tracking Algorithms

Galileo as a Tool for Precise Farming: Experience with GIOVE Signals Reception

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Galileo as a tool for precise farming: Experience with GIOVE signals reception.

Group Repetition Interval Selection and Core eLoran Service Capacity

  • Autoři: Šafář, J., Williams, P., Basker, S., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of 13th IAIN World Congress. Bergen: Nordic Institute of Navigation, 2009. pp. 1-12.
  • Rok: 2009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper we explore the effect of CRI on the positioning performance of an eLoran receiver, and assess the effectiveness of modern receiver CRI mitigation techniques. The resulting models are integrated into an updated GRI selection method and are used to analyse the capacity within the European region to accommodate new eLoran stations.

High performance Galileo E5 correlator design

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper compares various signal processing methods of the E5 signal from a simple one based on the separate signal component processing to an optimal one based on the processing of the whole signal power. The philosophy of the optimal processing method is firstly described on a simple example which is QPSK modulated navigation signal by the pilot and data signal. The correlator for QPSK modulation usually processes these two orthogonal components separately but the simultaneous processing of such signal is also possible. The problem of the second approach is signal replica generation because of its dependency on the navigation message.

High Performance Galileo E5 Receiver

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is focused on the signal processing methods of the complete AltBOC Galileo E5 signal.

Universal Front End for Software GNSS Receiver

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with the design of the high performance front end for GNSS software receiver. The various front end architectures are analyzed. The design of the complete analogue signal processing chain i.e. multi frequency antenna LNA, RF filters and configurable receiver for civil GPS and open Galileo signals are presented in the paper. The front end is based on the direct conversion receiver architecture. The frequency range of developed front end covers all L band GNSS signals. The bandwidth is controlled in range 8 - 66 MHz.

Fast Acquisition of the GLONASS Signal

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The characteristics of parallel search acquisition algorithms for the GLONASS signal are discussed in this paper for both coherent and non coherent processing.

Galileo AltBOC E5 Signal Characteristics for Optimal Tracking Algorithms

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper shows an analytical derivation of the cross corelation function of two AltBOC modulated signals, which differ in their data bits sequences or their secondary code phases.

Multi System Navigation Receiver

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    High demands on mobile user positioning cannot be satisfied by single navigation system. The paper proposes multi system solution which utilizes navigation and communication systems and signals. The experimental software receiver is described as development tool of such combined system.

Novinky v družicové navigaci

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Tento příspěvek přináší přehled nových trendů v oblasti družicové navigace.

OFDM Signal Navigation

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The aim of this study is to analyze the applicability of communication signals with OFDM modulation scheme for mobile user positioning based on ToA navigation method.

Some GNSS applications in the Czech Republic

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This contribution gives an overview of some GNSS applications in the Czech Republic.

Augmentation Methods for GNSS Integrity and Precision Enhancement in Difficult Environment

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The topic of the paper is to describe influences of the difficult environment to the GNSS and SBAS signals and consequences for signal processing. The satellite line of sight shadowing influence to signal reception is discussed for various environments together with proposed shadowing model. The model is derived from two state Markov model. The experimental measurements of mobile reception of EGNOS signal has shown the need of supporting SBAS signals in several environment by complementary transmission. Such concept of supporting system with data transmitted by separate channel is discussed in the paper both for DGNSS and SBAS case. The possibility and analysis of use of Internet for real time distribution of augmentation data is presented in the paper, namely questions of data latency and augmentation influence to user position in difficult environment.

DVB-T Signal Ranging

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with an alternative navigation method based on DVB-T signal ranging. The proposed signal processing is based on correlation reception using the continual carrier part of the DVB-T signal. The ranging properties of the proposed signal processing will be derived and verified by simulation and experiments with software DVB-T receiver.

Galileo and the Other Satellite Navigation Systems

  • Autoři: prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of 17th International Conference Radioelektronika 2007. Piscataway: Institute of Electrical and Electronic Engineers, 2007. pp. 3-6. ISBN 1-4244-0821-0.
  • Rok: 2007
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    GPS is the best-known satellite navigation system in the world. Next to GPS, a Russian system GLONASS is operating, and a European system Galileo is intensively prepared. The first satellite of the Galileo system should be launched in 2009, and the whole system Galileo should start to regularly operate in 2011 or 2012. Both in the community of researchers and in the public, questions about the accuracy, compatibility and helpfulness of those systems are discussed. Those questions are not only of the technical nature but also of the political one. The paper tries to give explanation of the principles of the operation of those systems, and their mutual comparison. At the end of the paper a concept of satellite navigation receiver designed at the Czech Technical University in Prague is sketched.

GPS/EGNOS/Galileo Software Receiver for Railway

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with possibility of integration of GNSS as a source of position information into the railway signalling system. It is focused on the use at secondary rail roads where it should substitute conventional ETCS signalling system. The description of the use of GNSS for safety critical applications is presented in the first part of the paper concerning possible influence of GNSS to the failures of the system and its investigation with the use of information or system redundancy. Design of a suitable GNSS receiver based on Software Defined Radio Concept (SDR) was realized in the frame of the project of the Czech Ministry of Transport. The various possible realizations of SDR and aspects of their use are analyzed. The design of the SDR based GNSS receiver for railway applications developed at the Czech Technical University is presented in the end of the paper.

Software Navigation Receivers for GNSS and DVB

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We describe the software GNSS receiver, its schema, implementation into a computer, results of tests and application for railway, municipal transportation and for shipping of dangerous matters. The receiver, originally for the Galileo system, is on a printed board which is the size of a Euro Card (160Í100 mm). Because the Galileo signal is not in the air, it was modified for the GPS and GLONASS systems. Experimental GNSS receiver (EGR) was used as a tool for its development and it is also described. Even if we use the receiver which is able to process signals of all three systems, it is impossible to ensure reception of GNSS signals in adverse conditions (under leaves canopy, in urban canyons, in hollow tracks, etc.). Therefore we have studied the possibilities of communication systems which will use modern signals known from satellite navigation and we have obtained very interesting results when we used DVB-T transmitters as beacons.

Software Navigation Receivers for GNSS and DVB

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We describe the software GNSS receiver, its schema, implementation into a computer, results of tests and application for railway, municipal transportation and for shipping of dangerous matters. The receiver, originally for the Galileo system, is on a printed board which is the size of a Euro Card (160x100 mm). Because the Galileo signal is not in the air, it was modified for the GPS and GLONASS systems. Experimental GNSS receiver (EGR) was used as a tool for its development and it is also described. Even if we use the receiver which is able to process signals of all three systems, it is impossible to ensure reception of GNSS signals in adverse conditions (under leaves canopy, in urban canyons, in hollow tracks, etc.). Therefore we have studied the possibilities of communication systems which will use modern signals known from satellite navigation and we have obtained very interesting results when we used DVB-T transmitters as beacons.

Software navigation receivers for GNSS and DVB

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We describe the software GNSS receiver, its schema, implementation into a computer, results of tests and application for railway, municipal transportation and for shipping of dangerous matters. The receiver, originally for the Galileo system, is on a printed board which is the size of a Euro Card (160?100 mm). Because the Galileo signal is not in the air, it was modified for the GPS and GLONASS systems. Experimental GNSS receiver (EGR) was used as a tool for its development and it is also described. Even if we use the receiver which is able to process signals of all three systems, it is impossible to ensure reception of GNSS signals in adverse conditions (under leaves canopy, in urban canyons, in hollow tracks, etc.). Therefore we have studied the possibilities of communication systems which will use modern signals known from satellite navigation and we have obtained very interesting results when we used DVB-T transmitters as beacons.

Software Navigation Receivers for GNSS and DVB

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We describe the software GNSS receiver, its schema, implementation into a computer, results of tests and application for railway, municipal transportation and for shipping of dangerous matters. The receiver, originally for the Galileo system, is on a printed board which is the size of a Euro Card (160? 100 mm). Because the Galileo signal is not in the air, it was modified for the GPS and GLONASS systems. Experimental GNSS receiver (EGR) was used as a tool for its development and it is also described. Even if we use the receiver which is able to process signals of all three systems, it is impossible to ensure reception of GNSS signals in adverse conditions (under leaves canopy, in urban canyons, in hollow tracks, etc.). Therefore we have studied the possibilities of communication systems which will use modern signals known from satellite navigation and we have obtained very interesting results when we used DVB-T transmitters as beacons.

Software Navigation Receivers for GNSS and DVB-T

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this article we describe a GNSS software receiver and the results from using DVB-T signals for navigation.

Availability of the EGNOS Service for a Land Mobile User

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The aim of this study is an analysis of the availability of the EGNOS service for a land mobile user, which is limited by the shadowing of the EGNOS satellites by the various obstacles. The shadowing process is modeled by the Markov process with model parameters determined for various environments by the mobile experimental measurements. The relevance of the model was also tested experimentally and the adequate conformity was observed. The availability of the EGNOS message reception in various environments was experimentally investigated and the statistics were calculated.

GNSS Signals Tracking Algorithms Performance Assessment Using GRT

Software GNSS Receiver for Signal Experiments

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with the experimental GNSS receiver built at the Czech Technical University for experiments with the real GNSS signal. The receiver is based on software defined radio architecture. Receiver consists of the RF front end and a digital processor based on programmable logic. Receiver RF front end supports GPS L1, L2, L5, WAAS/EGNOS, GALILEO L1, E5A, E5B signals as well as GLONASS L1 and L2 signals. The experimental receiver is also used in GNSS monitoring station, which is independent monitoring facility providing also raw monitoring data of the GPS, EGNOS and Galileo systems via internet.

Assessment of the EGNOS Signal Availability for Land Mobile User

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The EGNOS land mobile channel is analyzed in the paper. The shadowing of the EGNOS signal is modelled by two-state Markov process. The results of experimental mesurements of signal reception and model validation fro various enviroments is presented in the paper.

Družicové určování polohy

EGNOS Signal Availability Measurements for a Land Mobile User

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Comparison of theoretical models and prectical field tests of availability of EGNOS signal for land mobile user. The mathematical model of the satellite signal shadowing based on Markov process was developed and compared with results from experimantal measurements.

Experimental GNSS Receiver and it's Applications

Experimental GNSS Receiver and its Applications

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Paper presents experimental GNSS receiver based on software receiver architecture. FPGA devices with integrated processor cores are used in the design.

Galileo Multi Frequency Signal Processing

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The aim of the contribution is to study signal processing methods including multi frequency code and carrier phase tracking methods and compare them whit the classical approach. Research is also focused on reception of a signal in hard conditions. Special attention is given to the methods of multi frequency signal processing.

Galileo Receiver Core Technologies

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The Galileo Receiver is investigated in the frame of the GARDA project. The Galileo code and carrier tracking subtask of the Galileo Receiver Core Technologies is carried out at the Czech Technical University. The problem was analysed and split to the particular tasks. The aim of this paper is focused on BOC correlator architecture.

GNSS in the Czech Republic

GNSS Receiver for GLONASS Signal Reception

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with the latest version of Experimental GNSS receiver built at the Czech Technical University and describes integration of GLONASS signal processing to the receiver.

GNSS Software Receiver - A Versatile Platform for Navigation Systems Signals Processing

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper presents concept of software receiver for use as a development, implementation, and testing platform for GNSS signal processing.

Local Augmentation in GNSS

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    GPS usability and reliability in transport telematics applications are limited due to difficult signal propagation mainly in hilly terrain or in urban areas. Therefore, methods for GPS support by local infrastructure are developed. Integration of GPS with European system Galileo in near future may reduce the limitation significantly, but it brings several new problems, which may be solved efficiently by adequate local augmentation systems. The GSM-GPRS data channel is suitable for interconnecting of mobile telematics environment with a central point and for distribution of GPS/Galileo ephemeris and other supporting information as well. The Experimental Galileo receiver, which is developed at department of Radioelectronics, is suitable experimental platform for development and testing of GPS/Galileo augmentation techniques.

Satellite Navigation in the Czech Republic

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Satellite Navigation in the Czech Republic - CGSIC IISC Czech National Report 2005

Signal Acquisition and Tracking Methods in GNSS

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The GNSS position determination is based on the satellite-to-user distance measurement. GNSS satellites transmit the specially designed signal with spread spectrum modulation. The signal propagation delay is measured to obtain the distance information. Because the satellite orbital parameters are known, position and velocity of users receiver equipment is computed consecutively.

Using of Signal with BOC Modulation in GNSS

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The new form of spread spectrum modulation BOC is intended for modernized GPS and Galileo satellites. Correlation feature of the BOC signal requires modification of current signal processing algorithms in GNSS receivers.

Availability of the EGNOS System for a Land Mobile User

Experimental GNSS Receiver

Galileo Receiver Core Technologies

GPS Signal Search Algorithm for Difficult Environment

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    GPS indoor applications need powerful DSP techniques for processing of very weak signal. High parallel processing techniques are used for these purposes. This paper describes the effective GPS weak signal-searching algorithm designed for DSP implementation on FPGA.

Implementation of the GLONASS Signal-Processing Algorithm to the Experimental GNSS Receiver

Measurement of GNSS Signal Parameters in Difficult Environment

MVUB Estimator of Channel Parameters for Indoor GPS Navigation Based on Two Antennas Measurement

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with estimation of appropriate channel model for indoor GPS navigation. The need and purpose of such model is discussed. The su_cient information for channel description is channel time variant impulse response. Our estimation of channel impulse response is based on two antennas simultaneous signal measuring. The theoretical model of measurement is proposed and justified. Then the MVUB estimator of channel impulse response is derived from this model.

Present Satellite Radio Navigation Systems, Their Performance and User Receiver Concepts

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The contribution gives an overview of present and future navigation systems and their augmentations as GPS, GLONASS, GALILEO, WAAS, EGNOS, MSAT, QZSS, BEIDOU, GAGAN. Performance of systems depends on technical parameters and we will try to evaluate it and to present our opinion on advantages of them for different applications and in various situations (reception of week signals suffering from great attenuation under vegetation canopy, in urban canyons, influence of reflections and multipath). The last part of contribution deals an application of software radio technology for user receiver design and results obtained from experiments with different algorithms of processing of satellite navigation systems signals.

Reception of Signals of GLONASS System by Experimental GNSS Receiver

Signal Processing in CNS Systems

Signal Processing in Experimental GNSS Software Receiver

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper describes software design flow for signal processing in the Experimental GNSS Software Receiver.

Software Radio and Its Applications in GNSS

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with the Software Radio and its applications in processing of signals of satellite navigation systems. Modern Software Defined Radio (SDR) technology enables to digitalize and process radio signals in programmable digital circuits. The high power programmable DSP and FPGA are implemented. The benefit of discussed architecture is in a software definition of the function and parameters of radio electronic systems. This architecture can be used in GNSS for software implementation of processing procedures of new GNSS signals, like GPS L2 C/A, GPS L5 or Galileo.

Software Solution of GNSS Receiver

Differential and Assisted GPS via GSM-GPRS and Internet

Equipment for Determination of Dependence of GPS Signal Parameters on Environment Quality

Experimental GNSS Receiver Based on Software Defined Radio Architecture

Experimental GPS Software Receiver for Indoor Navigation

Experimental Software Receiver for Present and Future GNSS Sytems

  • Autoři: doc. Dr. Ing. Pavel Kovář, Kačmařík, P., Seidl, L., prof. Ing. František Vejražka, CSc.,
  • Publikace: International-Symposium of European Radio Navigation Networks Integration of GPS, EGNOS, Galileo and LORAN-C/EUROFIX Proceedings. Bonn: Deutsche Gesellschaft für Ortnung und Navigation (DGON), 2003.
  • Rok: 2003

Experimental Software Receiver of Signals of Satellite Navigation Systems

Signal processing in CNS systems

System for GPS Signal Analysis in Various Environments

The Experimental GNSS Receiver

5th International Student Conference on Electrical Engineering POSTER 2001

Compression and Coding Methods in Differential Global Navigation Satellite Systems

  • Autoři: prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of Workshop 2002. Praha: České vysoké učení technické v Praze, 2002, pp. 498-499. ISBN 80-01-02511-X.
  • Rok: 2002

Differential Measurement Methods in Global Satellite Navigation Systems

  • Autoři: Seidl, L., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of Workshop 2002. Praha: České vysoké učení technické v Praze, 2002, pp. 496-497. ISBN 80-01-02511-X.
  • Rok: 2002

Radio Systems for Real Time GNSS - Experimental GNSS Receiver

Určování polohy v mobilních komunikacích

4th International Student Conference on Electrical Engineering POSTER 2000

Augmentation of Satellite Navigation

  • Autoři: Vičan, M., Plášil, J., Seidl, L., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of Workshop 2001. Praha: České vysoké učení technické v Praze, 2001. pp. 317. ISBN 80-01-02335-4.
  • Rok: 2001

Digital Signal Processing Application in Radioelectronics

Družicové systémy určování polohy GPS, GLONASS, GALILEO a EGNOS, jejich současnost a budoucnost

Multipath Suppression Method Suitable for DGPS Reference Stations

  • Autoři: Plášil, J., Seidl, L., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of Workshop 2001. Praha: České vysoké učení technické v Praze, 2001. pp. 403. ISBN 80-01-02335-4.
  • Rok: 2001

Analysis of Radio Channels Usable for DGPS Correction Transmission and Proposals for the CEI Area

  • Autoři: Manzoni, G., Oszczak, S., prof. Ing. František Vejražka, CSc.,
  • Publikace: Workshop Bridging the Gap. Collection of Abstracts. Ljubljana: Institute of Geodesy, Cartography and Photogrammetry, 2000. pp. 45.
  • Rok: 2000

Application of Digital Signal Processing in Radio Engineering

Družicová navigace

Družicové systémy určování polohy pro přesné zemědělství

  • Autoři: prof. Ing. František Vejražka, CSc.,
  • Publikace: Ekonomické zemědělství. Přesné zemědělství. Sborník III. mez. odb. zem. konference. Luhačovice: TOKO, 2000. pp. 1-5.
  • Rok: 2000

Information Technology Research

Modulation Schemes for Wireless Access

Multipath Suppression Methods Suitable for DGNSS Reference Station

Satellite Navigation Systems GNSS1 and GNSS2

  • Autoři: prof. Ing. František Vejražka, CSc., Stoklasová, L., Seidl, L., Plášil, J., Vičan, M.
  • Publikace: Proceedings of Workshop 2000. Praha: České vysoké učení technické v Praze, 2000. pp. 197. ISBN 80-01-02229-3.
  • Rok: 2000

Současnost a budoucnost diferenčních metod určování polohy pomocí navigačních družic

Současný stav rádiové navigace

Status and Development of Satellite Positioning and Navigation Systems in Central and East European Countries

  • Autoři: Oszczak, S., Manzoni, G., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of the 8th European CGSIC IISC Meeting. Praha: České vysoké učení technické v Praze, 2000. pp. 113-123. ISBN 80-01-02135-1.
  • Rok: 2000

Integration of GPS Receiver with Heading Sensor and Odometer

Local Area DGPS/RTK Reference Station Networks in CEI Countries

Low Frequency DGPS Correction Dissemination System and EGNOS

  • Autoři: prof. Ing. František Vejražka, CSc.,
  • Publikace: DGPS Trieste. Workshop on Differential GPS and GLONASS Technique and Applications on Safety in Central Europe Initiative Area. Trieste: University Trieste, 1999. pp. 1-4.
  • Rok: 1999

Methods of Precision Position Determination by Satellite Navigation

One Year Experience with DGPS Correction Dissemination by Long Wave Transmitter

  • Autoři: prof. Ing. František Vejražka, CSc., Fišer, J., Seidl, L., Plášil, J.
  • Publikace: Reports in Geodesy and Geographical Information Systems. Gavle: National Land Survey of Sweden, 1999. pp. 224-227. ISSN 0280-5731.
  • Rok: 1999

Použití GPS v telekomunikacích I

Použití GPS v telekomunikacích II

Development of Equipment for DGPS/DGLONASS Corrections Dissemination

Družicová navigace

Družicové rádiové systémy pro určování polohy, jejich současný stav a budoucnost

Družicový navigační systém GPS a DGPS v České republice

  • Autoři: prof. Ing. František Vejražka, CSc., Richter, P., Fišer, J.
  • Publikace: Precizní zemědělství. Perspektivy a první zkušenosti v ČR. Praha: Česká zemědělská univerzita (ČZU), 1998, pp. 8-17.
  • Rok: 1998

Družicový navigační systém GPS a DGPS v České republice

  • Autoři: prof. Ing. František Vejražka, CSc., Fišer, J., Seidl, L., Richter, P.
  • Publikace: Transfer 98. Praha: České vysoké učení technické v Praze, 1998, pp. 135-136.
  • Rok: 1998

Kudy kráčí GPS a DGPS

Systém GPS, jeho aktuální stav a aplikace v České republice

  • Autoři: prof. Ing. František Vejražka, CSc., Fišer, J., Seidl, L., Richter, P., Špaček, J.
  • Publikace: Radiokomunikace '98. Pardubice: České radiokomunikace, 1998. pp. 1-15.
  • Rok: 1998

DGPS Corrections Dissemination Using LF Transmitters

  • Autoři: Fišer, J., Seidl, L., prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of the Conference GNSS'97. First European Symposium on Global Navigation Satellite Systems. München: The German Institute of Navigation, 1997, pp. 717-721.
  • Rok: 1997

Differential GPS Technology in Czech Republic

Long Wave System of DGPS Correction Dissemination in the Czech Republic

  • Autoři: prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of the Sixth CGSIC International Information Subcommittee European Meeting. Warszawa: Polish Academy of Sciences, 1997, pp. 1-11.
  • Rok: 1997

Suppression of Multipath Propagation in DGPS Receivers for Mobile Applications

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Potlačení vlivu mnohacestného šíření signálu v DGPS přijímačích pro mobilní aplikace

Suppression of Multipath Propagation in DGPS Receivers for Mobile Applications

Suppression of Multipath Propagation in DGPS Receivers for Mobile Applications

The DGPS Technology update in the Czech Republic: Long Wave System of DGPS Correction Dissemination in the Czech Republic

  • Autoři: prof. Ing. František Vejražka, CSc.,
  • Publikace: Proceedings of the Conference Civil GPS Service Interface Committee. Warszawa: Polish Academy of Sciences, 1997, pp. 199-209.
  • Rok: 1997

Differential Methods of Position Determination

Experimentální šíření korekcí DGPS pomocí RDS služby

Influence of the Construction of the Radiofrequency Part of the Navigation Receiver on the Interference Immunity

The Design of Radio Frequency Part of GPS/GLONASS Navigation Receiver for Differential Navigation

The DGPS Reference Station of the Czech Technical University

  • Autoři: Broum, M., Hrdina, Z., Pánek, P., Seidl, L., prof. Ing. František Vejražka, CSc.,
  • Publikace: 5th International Conference on Diferential Satellite Navigation Systems. St. Petersburg: The Russian Institute of Radionavigation and Time, 1996, pp. 631-634.
  • Rok: 1996

The Experimental Integrated GPS/GLONASS Receiver

A Comparison of Predicted and Measured Ionospheric Range Error Corrections

Assessment of Two Methods to Provide Ionospheric Range Error Corrections for Single-Frequency GPS Users

  • Autoři: Komjathy, A., Langley, R., prof. Ing. František Vejražka, CSc.,
  • Publikace: XXI General Assembly of International Union of Geodesy and Geophysics. Boulder: IUGG, 1995, pp. 1-18.
  • Rok: 1995

Decision Directed Channel State Estimator

Digital Audio Broadcasting Summary of the Present State of the Art

  • Autoři: Červenka, J., Míchal, J., Nerad, J., Srp, R., prof. Ing. František Vejražka, CSc.,
  • Publikace: Workshop 95. Praha: České vysoké učení technické v Praze, 1995, pp. 569-570.
  • Rok: 1995

Estimation of Ionosphere Delay Parameters for Wide Are Differential GPS Applications

  • Autoři: Broum, M., Hrdina, Z., Nagle, J., prof. Ing. František Vejražka, CSc., Zápotočny, J., Seidl, L.
  • Publikace: DSNS 95 - Differential satellite navigation systems. Bergen: Nordic Institute of Navigation, 1995, pp. 91-98.
  • Rok: 1995

Estimation of Ionosphere Delay, Parameters for Wide Area Differential GPS Applications

  • Autoři: Broum, M., Hrdina, Z., prof. Ing. František Vejražka, CSc., Seidl, L., Zápotočny, J.
  • Publikace: Elektro 95. Žilina: VŠDS, 1995, pp. 203-206. ISBN 80-7100-251-8.
  • Rok: 1995

Influence of the Construction of the Radiofrequency Part of the Navigation Receiver on the Interference Immunity

Ionospheric Delay Prediction for Wide Area DGPS Users

  • Autoři: prof. Ing. František Vejražka, CSc., Broum, M., Hrdina, Z., Seidl, L., Obuškevič, V., Zápotočny, J.
  • Publikace: Workshop 95. Praha: České vysoké učení technické v Praze, 1995, pp. 597-598.
  • Rok: 1995

Methods of Measurement and Compensation of Phase and Frequency Drift of the DGPS Master Station Oscillator

  • Autoři: Broum, M., Hrdina, Z., Nagle, J., prof. Ing. František Vejražka, CSc., Zápotočny, J., Seidl, L.
  • Publikace: DSNS 95 - Differential satellite navigation systems. Bergen: Nordic Institute of Navigation, 1995, pp. 101-108.
  • Rok: 1995

Přenos korekcí DGPS na dlouhých a středních vlnách

Chyby v družicových systémech určování polohy

  • Autoři: prof. Ing. František Vejražka, CSc., Hrdina, Z., Broum, M., Seidl, L., Zápotočny, J.
  • Publikace: Nové směry ve zpracování signálů. Liptovský Mikuláš: Vojenská akadémia, 1994, pp. 184-187. ISBN 80-233-0346-5.
  • Rok: 1994

Družicová rádiová navigace

GPS & Glonass Navigation Receiver

  • Autoři: Broum, M., Hrdina, Z., Seidl, L., prof. Ing. František Vejražka, CSc., Zápotočny, J.
  • Publikace: CTU Seminar 94. Praha: České vysoké učení technické v Praze, 1994, pp. 189-190.
  • Rok: 1994

Modernization of PhD. Studies in Radioelectronics

Predikce ionosférického zpoždění pro uživatele velkoplošného diferenčního GPS

  • Autoři: prof. Ing. František Vejražka, CSc., Broum, M., Hrdina, Z., Obuškevič, V., Seidl, L., Zápotočny, J.
  • Publikace: Radioelektronika 94 Sborník referátů. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 1994, pp. 244-247.
  • Rok: 1994

Tolerance odhadu přesnosti určení polohy v rádiových navigačních systémech

Diferenční určování polohy pomocí družicového navigačního systému NAVSTAR.3

Performance of GPS and GLONASS Systems Supported by INMARSAT Satellites

Performance of GPS and GLONASS Systems Supported by INMARSAT Satellites

Precision Time and Frequency Generation by GPS-Navstar Receiver

  • Autoři: prof. Ing. František Vejražka, CSc., Hrdina, Z., Seidl, L., Fiala, J., Pánek, P.
  • Publikace: Workshop 93. Praha: České vysoké učení technické v Praze, 1993, pp. 205-206.
  • Rok: 1993

Za stránku zodpovídá: Ing. Mgr. Radovan Suk