The goal of this paper is to demonstrate the capability of the 1U CubeSat to study the radiation spectra on LEO. The research was realized by the Lucky-7 mission with the primary goal of testing electronics such as a power supply, piNAV L1 GPS receiver, UHF communication system, and other subsystems in the natural space environment, and the secondary goal of testing the possibility of using 1U CubSat class satellites for scientific tasks. The satellite is equipped with a piNAV GPS receiver and piDOSE radiation detector, silicon diode radiation spectrometer, camera, and other sensors. The on-board computer enables storage of 34 h of measurements of the radiation spectrum. These measurements can be downloaded by the UHF communication system during four satellite passes over the monitoring ground station. We successfully verified all necessary instruments and their cooperation and measurement procedure. The UHF communication was identified as the most critical subsystem because of its low capacity, which slowed down the satellite operation. We needed four zenith passes to upload 34 h of measurement.
Study of the Two-Line Element Accuracy by 1U CubeSat with a GPS Receiver
There is a common practice to calculate orbital trajectories of space objects like satellites and space debris using Two-Line Element Sets (TLEs). However, TLEs provide rather coarse parameters for fine orbit computation and their precision varies with age of their issue and position of the satellite. The paper evaluates such induced position determination error using the comparison of a position calculated from TLE data for a small CubeSat class satellite and a position obtained from the on-board custom GPS receiver that is a part of such satellite payload. The analyses of the impact of satellite position at the orbit, i.e., a dependency of position error on satellite geographical latitude, and impact of the ageing of TLE data in frame of position and velocity vector were made. There was shown that use of TLE data can bring some significant errors in calculation of predicted satellite position which can affect performance and efficiency of some related tasks like steering the ground station antenna for communication with the satellite or planning the satellites operations namely for the classes of small and amateur satellites.
PDOP parameters improvement using multi-GNSS and signal re-transmission at lunar distances
Precise navigation for satellites of any kind is the key to future cost-effective Lunar missions. The usability of Global Navigation Satellite Systems (GNSS) for such high-altitude applications is still challenging due to reduced signal power levels, satellites visibility or signal processing complexity with all that resulting in a low position, velocity and time (PVT) accuracy, which is typically expressed by geometric dilution of precision (GDOP) parameters. This paper proposes a navigation method based on re-transmission combined with multi-GNSS concept, specifically signal reception from GPS, Galileo, Glonass, BeiDou and SBAS satellites’ antenna pattern main-lobes and side-lobes. Those signals are re-transmitted from the user satellite at the Lunar distance to the Earth, where all the signal processing is assumed to be performed. Based on the results from the tests of the of modelled scenario, the method presents an improvement of the position dilution of precision (PDOP, a subset of GDOP) parameters for the missions at the Lunar distance.
VHF/UHF Transceiver with Digital Signal Processing
The innovative approach in designing the radio part of the professional VHF/UHF (narrow-band) transceivers based on the application of the digital intermediate frequency stages known from the wide-band systems is presented. The main problem is the dynamic range of the analog to digital converter, which is the weakest part of the concept. The combination of the presented common analog RF front end and digital implementation of the further receiver stages improves production repeatability and reduces production and setup costs and the final size of the transceiver in comparison to pure analog design. We presented the parameters of the key blocks, which are RF filters and Digital Down Converter including analog to digital converter, that substantially contribute to the complete design. The proper selection and design of such parts show the valuable impact to the proposed approach of digital signal processing based transceiver.
New Accuracy Testing of the Lightning VHF Interferometer by an Artificial Intercloud Pulse Generator
The authors have rearranged an optimal method for signal processing of interferometric measurements, based on the angle-of-arrival estimation approach, and have analyzed errors of estimating the direction of arrival of intercloud pulse signals. The method was then implemented in the performance of optimized interferometer hardware. This article presents application of an array of plate antennas matched by the 50 omega parallel resistor that are directly connected to 50-omega high-frequency low-noise amplifiers for each channel. The important contribution of the authors is to cover the plate antenna capacitance to the input bandpass filter. The proposed compensation enables to reduce linear distortion of the received signal, which is one of the main sources of errors of the time-of-arrival estimation, and to optimize the antenna impulse response. The novelty of this article can be seen in the application of the artificial intercloud pulse generator for testing, precision calibration of the proposed system, and fixing of potential imperfections and losses in both hardware and processing software. The practical application of the proposed interferometer is demonstrated on the processing of real lightning events. As the interferometer operates in the frequency bands that are dedicated to other radio communication services, this article provides results for measurements of interference that were realized with the aim of finding an optimal installation location.
Radiation Data Acquisition with Research Stratospheric Balloon Incorporating IoT Telemetry System
he paper presents a radiation data measured in the atmosphere during the flight of a stratospheric balloon. The balloon carries the third version of the gondola with custom-developed electronic device integrating GPS, IoT, data storage and gamma radiationsensors. The radiation is measured by a miniature low-power silicon detector equipped with the plastic scintillator. The gondola enables to track the balloon during the whole stratospheric flight. The IoT network simplifies reception of the telemetry dataon the ground.
Testing Signal Processing Techniques for Digital VHF/UHF Transceiver in High-level SDR Programming Environment
Nowadays, due to cost savings, flexibility or improvement of service quality, modern communication devices solely rely on the digital domain when it comes to signal processing. The paper presents a comfortable, fast and straightforward approach of testing and verifying developed digital signal processing techniques before their implementation into a digital mobile transceiver. The approach benefits from the concept of an Software-defined radio (SDR) by employing a high-level programming environment capable of direct analog radio frequency (RF) front end control in real-time via a user defined software.
Digital Up and Down Converter for High Performance VHF and UHF transceiver
The Digital Up and Down Converter (DUC/DDC) is a basic building part of the professional digital mobile transceiver. The paper presents DDC/DDS for dual mode professional VHF/UHF transceiver developed for railway radio. The transceiver complies ETSI standards for NFM and Digital Mobile Radio (DMR). The DUC/DDC is featured with the channel selectivity exceeding 70 dB and dynamic range more than 90 dB. The implementation of the other standards that use constant envelope modulation like small satellite UHF communication links is also possible.
High Performance SDR for Monitoring System for GNSS Jamming Localization
This paper presents a basic description of a monitoring system which is designed for the GNSS jamming detection and localization as well as giving the theoretical issue together with specific consequences. The usage of that system is targeted to an aviation safety and space together with general transportation. The system is an extensive project, and this document is mainly about measuring station as an essential part of it. The paper presents specific localization techniques which will be used in digital signal processing. Several tests of the functionality of the measuring station have been made and presented in this paper. The result of the paper comes from the basic test of the measuring station. In that test, functionality - clock synchronization, mutual phase of an antenna array, software-defined radio was proved. The monitoring system is still developing and other important results will be described in the future.
Modernized solar radio spectrograph in the L band based on software defined radio
The paper presents the concept, implementation, and test operation of a modernized solar radio spectrograph for an investigation of the solar emission and solar bursts in radio frequency bands. Besides having a strong diagnostic significance for studying the flare energy release, the solar radio bursts can also cause strong interference for radio communication and navigation systems. The current spectrograph for the Ondrejov observatory (Astronomical Institute of Czech Academy of Sciences) was modernized by using a direct-conversion receiver connected to a field-programmable gate array (FPGA) for the fast Fourier transform (FFT) spectrum estimation and put into the test operation. The higher time and frequency resolution and lower noise in comparison with the existing analog instrument were reached by the implementation of the latest optimal signal processing methods. To reduce the costs for such modernization, the operating frequency range was divided into four sub-bands of bandwidth 250 MHz, which brings another benefit of greater scalability. The first observations obtained by the new spectrograph and their comparison with the analog device are presented in the paper with future steps to put the spectrograph into the regular operation.
GNSS systems are susceptible to radio interference despite then operating in a spread spectrum. The commerce jammers power up to 2 watts that can block the receiver function at a distance of up to 15 kilometers in free space.
Telemetry System of FIK III. Stratospheric Balloon
The paper presents design and application of a telemetry system for stratospheric balloon based on Internet of Things System of SigFox. The purpose of the telemetry system is balloon tracking during the stratospheric flight. It was tested on experimental flight of FIK III stratospheric balloon equipped with SigFox as main transmitter and UHF transmitter for backup. The payload consisted of ADS-B receiver, and two independent dosimeters for radiation measurement. The paper presents verification of operation of telemetry system on results obtained during experiment. The end of paper covers also some considerations about advantages and drawbacks of such solution.
A new assessment method of pHEMT models by comparing relative errors of drain current and its derivatives up to the third order
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.
Experimental SDR receiver for monitoring and processing of solar radio bursts
The paper introduces a design of radio spectrography receiver that shall serve as equipment for reception, monitoring, and processing of solar radio bursts. These burst can affect operation of many radio communication and navigation services as is presented on example of GPS satellites signal degradation. The concept and design of the spectrography receiver is presented together with discussion of hardware requirements and proposed solution.
Telemetry system for research stratospheric balloon
The paper presents telemetry system for stratospheric balloon mission based on the UHF transceivers designed for Internet of Things. The system operates in 869.5 MHz frequency band. The system uses very short packet without channel coding that can be successfully received and decoded under low signal to noise ratio. The modem sensitivity −124 dBm and the transmission power 25 dBm can ensure reliable communication for distances longer than 100 km with omnidirectional antennas and 200 km with 10 dBi ground station directional antenna. The telemetry system uses GFSK modulation of bit rate 1200 Bd and is designed for a transmission of the balloon position and status.
A new assessment of pHEMT models by comparing relative errors of drain current and its derivatives up to the third order
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.
ADS-B Reception at Airport Airside Areas using TDL-based Channel Modeling
In this paper we introduce an approach to reception and processing of the ADS-B extended squitter signals provided by aircrafts and other vehicles on the airport airside area. The paper presents a method for use channel modelling based on TDL model for purposes of ADS-B signal processing enhancement. The model tests are based on real data measurements at Prague airport. The method for application of this approach and verification tests are presented as well.
Estimation of parameters for ground ADS-B radio channel model
We propose the model of radio channel for ADS-B signal reception at the ground area of airport, which is typical by interference caused by multipath propagation. The model is based on a tapped delay line (TDL) model. The source data for model parameters estimation are obtained by measurements at Prague Vaclav Havel airport. We compare simulated results based on proposed model with experimental measurements.
Empirical Model of the ADS-B Channel for Airport Area
The paper describes approach to processing of the ADS-B extended squitter signals and data provided by targets on the ground area of the airport. These signals are affected by radio channel environment which causes distortion and interference. The paper presents a method for estimation of the channel TDL model based on empirical data processing. This method is applied on measurement and processing campaign with the real signals from MLAT transmitters at the Prague Vaclav Havel airport. The results of channel model parameters are presented here as well.
Dual-frequency Tracking of Compass Signals: Compass Implementation to the Witch Navigator Receiver
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.
Augmentation Methods for GNSS Integrity and Precision Enhancement in Difficult Environment
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.
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.
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.
The paper deals with the reception, processing, statistical evaluation and archiving of EGNOS (European Geostationary
Navigation Overlay Service) signals together with data of present and future GNSS (GPS, GLONASS, and Galileo).
Satellite Navigation Applications in Indoor Environment
Project investigates problems and limitations of use of satellite navigation in difficult environment, e.g. indoors. It suggests possible solutions by augmentation of the present systems with additional data enabling operation under hard conditions.
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.
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.
Proceedings of the 7th International Navigational Symposium on Marine Navigation and Safety of Sea Transportation. Gdynia/Jurata: Gdynia Maritime University, Faculty of Marine Electrical Engineering, 2007.
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.
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.
This paper presents an overview of aspects that have to be taken into account in use of GNSS receivers for positioning in the difficult environment, for example indoors. The performing position determination and navigation tasks in such environments come nowadays more and more in the focus of the GNSS community. The GNSS signal indoor reception is affected by strong attenuation and due to the nature of the environment by strong multipath. The paper discusses both of them and their possible impact to the navigation tasks. The effect of the user movement is discussed and the experimental measurements are presented. The measurements were realized with use of experimental GNSS software receiver, described in the paper as well.
Design methods for RF part of GNSS software receivers
Global Navigation Satellite Systems (GNSS) play vital role in the area of position determination and navigation both in transport applications but also in other areas of common life. The reception of EGNOS, SBAS improving GNSS to make them suitable for safety critical applications, suffers in various environments from unavailability of the signal. The paper deals with a possibility to complement satellite signal with data disseminated by alternative methods.
The paper explains implementation of the frond-end part for experimental GNSS software receiver developed at the Department of Radioelectronics. The experimental GNSS receiver is based on Software Defined Radio (SDR) concept. Receiver is designed for the processing of signals of present and future global navigation satellite systems, including GPS, GLONASS and Galileo. For the biggest possible versatility, the modular architecture was chosen. The front-end unit consists of three independent channels with the bandwidth of 24 MHz. Single conversion super-heterodyne concept with intermediate frequency 140 MHz is used. Front-end provides down converted analogue signal to DSP unit represented by FPGA device with two embedded PowerPC cores.
Assessment of the EGNOS Signal Availability for Land Mobile User
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.
EGNOS Signal Availability Measurements for a Land Mobile User
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.
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.
GNSS Software Receiver - A Versatile Platform for Navigation Systems Signals Processing
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.
Overview of the Experimental GNSS Software Receiver Design Issues
SDR concept is prospective approach to signal processing in radio systems, including navigation systems. The advantage of software oriented approach resides in easy configuration and modification of signal processing algorithms.
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.
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.
The contribution presents continuous position determination algorithm for land navigation applications. The focus is on adaptive algorithm based on primary satellite navigation receiver and several additional positioning sensors with their error models adjusted by using special characteristics of a vehicle movement. The primary position measurement is affected by obstacles in urban areas, heavy foliage, etc. Under such conditions, the additional sensors extrapolate change of movement from the last known position. The disadvantage of relative sensors is in their ageing accuracy that leads to poor results with increasing time. This behaviour results in an accumulation of sensor errors in projected trajectory. In the consequence of this accumulation, position error increases unboundedly with the time...