scholarly journals 2-D Coherent Integration Processing and Detecting of Aircrafts Using GNSS-Based Passive Radar

2018 ◽  
Vol 10 (7) ◽  
pp. 1164 ◽  
Author(s):  
Hong-Cheng Zeng ◽  
Jie Chen ◽  
Peng-Bo Wang ◽  
Wei Yang ◽  
Wei Liu
Keyword(s):  
Matched Filter ◽  
Power Level ◽  
Doppler Frequency ◽  
Satellite System ◽  
Passive Radar ◽  
Match Filter ◽  
Coherent Integration ◽  
Long Time ◽  
Global Navigation Satellite ◽  
Aircraft Detection

Long time coherent integration is a vital method for improving the detection ability of global navigation satellite system (GNSS)-based passive radar, because the GNSS signal is not radar-designed and its power level is very low. For aircraft detection, the large range cell migration (RCM) and Doppler frequency migration (DFM) will seriously affect the coherent processing of azimuth signals, and the traditional range match filter will also be mismatched due to the Doppler-intolerant characteristic of GNSS signals. Accordingly, the energy loss of 2-dimensional (2-D) coherent processing is inevitable in traditional methods. In this paper, a novel 2-D coherent integration processing and algorithm for aircraft target detection is proposed. For azimuth processing, a modified Radon Fourier Transform (RFT) with range-walk removal and Doppler rate estimation is performed. In respect to range compression, a modified matched filter with a shifting Doppler is applied. As a result, the signal will be accurately focused in the range-Doppler domain, and a sufficiently high SNR can be obtained for aircraft detection with a moving target detector. Numerical simulations demonstrate that the range-Doppler parameters of an aircraft target can be obtained, and the position and velocity of the aircraft can be estimated accurately by multiple observation geometries due to abundant GNSS resources. The experimental results also illustrate that the blind Doppler sidelobe is suppressed effectively and the proposed algorithm has a good performance even in the presence of Doppler ambiguity.

scholarly journals Moving Target Detection in Multi-Static GNSS-Based Passive Radar Based on Multi-Bernoulli Filter

2020 ◽  
Vol 12 (21) ◽  
pp. 3495
Author(s):  
HongCheng Zeng ◽  
Jie Chen ◽  
PengBo Wang ◽  
Wei Liu ◽  
XinKai Zhou ◽  
...  
Keyword(s):  
Target Detection ◽  
Sequential Monte Carlo ◽  
Signal To Noise Ratio ◽  
Power Level ◽  
Estimation Method ◽  
Satellite System ◽  
Moving Target ◽  
Passive Radar ◽  
Moving Target Detection ◽  
Global Navigation Satellite

Over the past few years, the global navigation satellite system (GNSS)-based passive radar (GBPR) has attracted more and more attention and has developed very quickly. However, the low power level of GNSS signal limits its application. To enhance the ability of moving target detection, a multi-static GBPR (MsGBPR) system is considered in this paper, and a modified iterated-corrector multi-Bernoulli (ICMB) filter is also proposed. The likelihood ratio model of the MsGBPR with range-Doppler map is first presented. Then, a signal-to-noise ratio (SNR) online estimation method is proposed, which can estimate the fluctuating and unknown map SNR effectively. After that, a modified ICMB filter and its sequential Monte Carlo (SMC) implementation are proposed, which can update all measurements from multi-transmitters in the optimum order (ascending order). Moreover, based on the proposed method, a moving target detecting framework using MsGBPR data is also presented. Finally, performance of the proposed method is demonstrated by numerical simulations and preliminary experimental results, and it is shown that the position and velocity of the moving target can be estimated accurately.

scholarly journals Sparse GLONASS Signal Acquisition Based on Compressive Sensing and Multiple Measurement Vectors

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Guodong He ◽  
Maozhong Song ◽  
Shanshan Zhang ◽  
Peng Song ◽  
Xinwen Shu
Keyword(s):  
Compressive Sensing ◽  
Satellite System ◽  
New Method ◽  
Signal Acquisition ◽  
Multiple Measurement ◽  
Multiple Measurement Vectors ◽  
Navigation Data ◽  
Long Time ◽  
Global Navigation Satellite ◽  
Sparse Features

A sparse global navigation satellite system (GLONASS) signal acquisition method based on compressive sensing and multiple measurement vectors is proposed. The nonsparse GLONASS signal can be represented sparsely on our proposed dictionary which is designed based on the signal feature. Then, the GLONASS signal is sensed by a normalized orthogonal random matrix and acquired by the improved multiple measurement vectors acquisition algorithm. There are 10 cycles of pseudorandom codes in a navigation message, and these 10 pseudorandom codes have the same row sparse structure. So, the acquisition probability can be raised by row sparse features theoretically. A large number of simulated GLONASS signal experiments show that the acquisition probability increases with the increase in the measurement vector column dimension. Finally, the practical availability of the new method is verified by acquisition experiments with the real record GLONASS signal. The new method can reduce the storage space and energy loss of data transmission. We hope that the new method can be applied to field receivers that need to record and transmit navigation data for a long time.

scholarly journals Signal-to-Noise Ratio Analyses of Spaceborne GNSS-Reflectometry from Galileo and BeiDou Satellites

2021 ◽  
Vol 14 (1) ◽  
pp. 35
Author(s):  
Yang Nan ◽  
Shirong Ye ◽  
Jingnan Liu ◽  
Bofeng Guo ◽  
Shuangcheng Zhang ◽  
...  
Keyword(s):  
Global Navigation Satellite System ◽  
Signal To Noise Ratio ◽  
Satellite System ◽  
Integration Time ◽  
Navigation Satellite ◽  
Signal To Noise ◽  
Coherent Integration ◽  
Global Navigation ◽  
Coherent Integration Time ◽  
Global Navigation Satellite

In recent years, Global Navigation Satellite System Reflectometry (GNSS-R) technology has made considerable progress with the increasing of GNSS-R satellites in orbit, the improvements of GNSS-R data processing technology, and the expansion of its geophysical applications. Meanwhile, with the modernization and evolution of GNSS systems, more signal sources and signal modulation modes are available. The effective use of the signals at different frequencies or from new GNSS systems can improve the accuracy, reliability, and resolution of the GNSS-R data products. This paper analyses the signal-to-noise ratio (SNR) of the GNSS-R measurements from Galileo and BeiDou-3 (BDS-3) systems, which is one of the important indicators to measure the quality of GNSS-R data. The multi-GNSS (GPS, Galileo and BDS-3) complex waveform products generated from the raw intermediate frequency data from TechDemoSat-1 (TDS-1) satellite and Cyclone Global Navigation Satellite System (CYGNSS) constellation are used for such analyses. The SNR and normalized SNR (NSNR) of the reflected signals from Galileo and BDS-3 satellites are compared to these from GPS. Preliminary results show that the GNSS-R SNRs from Galileo and BDS-3 are ∼1–2 dB lower than the GNSS-R measurements from GPS, which could be due to the power of the transmitted power and the bandwidth of the receiver. In addition, the effect of coherent integration time on GNSS-R SNR is also assessed for different GNSS signals. It is shown that the SNR of the reflected signals can be improved by using longer coherent integration time (∼0.4–0.8 dB with 2 ms coherent integration and ∼0.6–1.2 dB with 4 ms coherent integration). In addition, it is also shown that the SNR can be improved more efficiently (∼0.2–0.4 dB) for reflected BDS-3 and Galileo signals than for GPS. These results can provide useful references for the design of future spaceborne GNSS-R instrument compatible with reflections from multi-GNSS constellations.

scholarly journals Spatial Characterization of GNSS Multipath Channels

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Hatef Keshvadi ◽  
Ali Broumandan ◽  
Gérard Lachapelle
Keyword(s):  
Fading Channels ◽  
Multipath Fading ◽  
Satellite System ◽  
Handheld Devices ◽  
Angle Of Arrival ◽  
Multipath Fading Channel ◽  
Coherent Integration ◽  
Global Navigation Satellite ◽  
Beamforming Technique

There is a growing interest in detecting and processing Global Navigation Satellite System (GNSS) signals in indoors and urban canyons by handheld devices. To overcome the signal attenuation problem in such adverse fading environments, long coherent integration is normally used. Moving the antenna arbitrarily while collecting signals is generally avoided as it temporally decorrelates the signals and limits the coherent integration gain. This decorrelation is a function of the antenna displacement and geometry of reflectors and angle of arrival of the received signal. Hence, to have an optimum receiver processing strategy it is crucial to characterize the multipath fading channel parameters. Herein, Angle of Arrival (AoA) and Angle Spread (AS) along with signal spatial correlation coefficient and fading intensity in GNSS multipath indoor channels are defined and quantified theoretically and practically. A synthetic uniform circular array utilizing a right-hand circular polarized (RHCP) antenna has been used to measure the spatial characteristics of indoor GNSS fading channels. Furthermore, rotating effect of a circular polarized antenna on the synthetic array processing and AoA estimation has been characterized. The performance of the beamforming technique via array gain is also assessed to explore the advantages and limitations of beamforming in fading conditions.

scholarly journals Case study on complex sporadic E layers observed by GPS radio occultations

2014 ◽  
Vol 7 (9) ◽  
pp. 9203-9236 ◽  
Author(s):  
X. Yue ◽  
W. S. Schreiner ◽  
Z. Zeng ◽  
Y.-H. Kuo ◽  
X. Xue
Keyword(s):  
Satellite System ◽  
Time Interval ◽  
Long Distance ◽  
Shear Theory ◽  
Long Time ◽  
Distance Communication ◽  
Statistical Studies ◽  
Sporadic E ◽  
Global Navigation Satellite ◽  
Event Based

Abstract. The occurrence of sporadic E (Es) layer has been a hot scientific topic for a long time. Global Navigation Satellite System (GNSS) based Radio Occultation (RO) has been proven a powerful technique on detecting the global Es layers. In this paper, we focus on some cases of complex Es layers based on the RO data from multiple missions processed in UCAR/CDAAC. We first show some examples of multiple Es layers occurred in one RO event. Based on the evaluations between co-located simultaneous RO events and between RO and Lidar observations, it could be concluded that some of these do manifest the multiple Es layered structures. We then show a case of the occurrence of Es in a broad region during a certain time interval. The result is then validated by the independent ionosondes observations. These complex Es structures could be understood well by the popular wind shear theory. We could map the global Es occurrence routinely in the near future given that more RO data will be available. Further statistical studies will enhance our understanding on the Es mechanism. The specification on Es should benefit both the Es based long distance communication and accurate neutral RO retrievals.

scholarly journals The Unbiased Characteristic of Doppler Frequency in GNSS Antenna Array Processing

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Yuchen Xie ◽  
Zhengrong Li ◽  
Feiqiang Chen ◽  
Huaming Chen ◽  
Feixue Wang
Keyword(s):  
Antenna Array ◽  
Carrier Phase ◽  
Array Processing ◽  
Doppler Frequency ◽  
Low Complexity ◽  
Satellite System ◽  
Accurate Estimation ◽  
Array Technology ◽  
Gnss Receivers ◽  
Global Navigation Satellite

The antenna array technology, especially the spaced-time array processing (STAP), is one of the effective methods used in Global Navigation Satellite System (GNSS) receivers to refrain the power of jamming and enhance the performance of receivers in the circumstance of interference. However, biases induced to the receiver because of many reasons, including characteristic of antennas, front-end channel electronics, and space-time filtering, are extremely harmful to the high precise positioning of receivers. Although plenty of works have been done to calibrate the antenna and to mitigate these biases, achieving a good performance of antijamming, high accuracy, and low complexity at the same time still remains challenging. Different from existing works, this paper leverages the characteristic of GNSS signal’s Doppler frequency in STAP, which is proven to remain unbiased to solve the problem, even when the nonideal antennas are used and the interference circumstance changes. Since the integration of frequency is carrier phase, the unbiased Doppler frequency leads to an accurate estimation of carrier phase which can be used to calibrate the antenna array without extra apparatus or complicating algorithms. Therefore, a simple Doppler-aid strategy may be developed in the future to solve the difficulty of STAP bias mitigation.

Diverse Signals Combinations for High-Sensitivity GNSS

2007 ◽  
Vol 60 (3) ◽  
pp. 497-515 ◽  
Author(s):  
Rigas T. Ioannides ◽  
L. Enrique Aguado ◽  
Gary Brodin
Keyword(s):  
High Sensitivity ◽  
Local Oscillator ◽  
Satellite System ◽  
Indoor Positioning ◽  
Signal Energy ◽  
Additional Signal ◽  
Coherent Integration ◽  
Integration Period ◽  
The Stability ◽  
Global Navigation Satellite

Indoor positioning imposes demanding requirements on the design of Global Navigation Satellite System (GNSS) sensors for both the acquisition and tracking functions. Although different combinations of coherent and non-coherent integration periods of a GNSS signal can be used to achieve reliable acquisition of the GNSS signals and indoors positioning, there are limitations to the extent that the integration period of the signal energy can be increased set by the receiver and satellite dynamics and the stability of the local oscillator. Assisting networks for GNSS applications (AGNSS) provide users with the capability of using long integration periods, enabling them to acquire indoor signals at low Carrier to Noise Ratio (CNR) values, where CNR is defined as the ratio of the received signal power over the noise density in units of dB-Hz. In this work we propose and evaluate the potential of a new method that will provide the user with an additional signal energy margin for accurate and reliable indoor positioning, with or without relying on assisted GNSS-type algorithms. The technique proposed here is based on the coherent and non-coherent combination of the energy of signals transmitted from the same GNSS satellite on different frequencies using the multiple open service signals that are to be provided by the Galileo system and under the GPS modernisation. This paper shows the improvement to the receiver acquisition and tracking performance using the proposed technique of combining energies at the L1, L2 and L5 bands for both data and pilot signals.

Generalised Theory on the Effects of Sampling Frequency on GNSS Code Tracking

2017 ◽  
Vol 71 (2) ◽  
pp. 257-280 ◽  
Author(s):  
Vinh T. Tran ◽  
Nagaraj C. Shivaramaiah ◽  
Thuan D. Nguyen ◽  
Joon W. Cheong ◽  
Eamonn P. Glennon ◽  
...  
Keyword(s):  
Tracking Error ◽  
Satellite System ◽  
Sampling Frequency ◽  
Code Rate ◽  
Integer Multiple ◽  
Delay Locked Loop ◽  
Coherent Integration ◽  
Baseband Signal Processing ◽  
Residual Code ◽  
Global Navigation Satellite

Synchronisation of the received Pseudorandom (PRN) code and its locally generated replica is fundamental when estimating user position in Global Navigation Satellite System (GNSS) receivers. It has been observed through experiments that user position accuracy decreases if sampling frequency is an integer multiple of the nominal code rate. This paper provides an accuracy analysis based on the number of samples and the residual code phase of each code chip. The outcomes reveal that the distribution of residual code phases in the code phase range [0, 1/ns), where ns is the number of samples per code chip, is the root cause of accuracy degradation, rather than the ratio between sampling frequency and nominal code rate. Doppler frequencies, coherent integration periods, front-end filter bandwidths and received Carrier to Noise ratios (C/N0) also influence receiver accuracy. Also provided are a sampling frequency selection guideline and new proposed estimates of the correlation output and the Delay Locked Loop (DLL) tracking error, which can be applied to precisely model GNSS receiver baseband signal processing.

Galileo E5 Signal Acquisition using Intermediate Coherent Integration Time

2019 ◽  
Vol 72 (3) ◽  
pp. 555-574
Author(s):  
Jérôme Leclère ◽  
René Landry
Keyword(s):  
Partial Correlation ◽  
Correlation Method ◽  
Satellite System ◽  
Integration Time ◽  
Signal Acquisition ◽  
Coherent Integration ◽  
L5 Signal ◽  
Galileo E5 ◽  
Low Sensitivity ◽  
Global Navigation Satellite

The acquisition of modern Global Navigation Satellite System (GNSS) signals may be difficult due to the presence of a secondary code. Indeed, short coherent integration times should be used without non-coherent integration, which implies a low sensitivity; or long coherent integration times should be used, requiring synchronisation with the secondary code and thus a full correlation, which implies a significant computational burden, especially for signals with long secondary codes such as the Galileo E5 signal. A third option that lies between the previous two is to perform a partial correlation using less than one secondary code period as input, however this is less efficient in terms of complexity than using an entire secondary code period, and the code's autocorrelation properties are completely changed. The authors recently proposed a method based on combining secondary code correlations, allowing the use of intermediate coherent integration times with the possibility to do non-coherent integrations, and the method was successfully applied to the Global Positioning System (GPS) L5 signal. This paper studies the application of the method to the Galileo E5 signal, compares it with the partial correlation method, and discusses the case where less than one secondary code period is used as an input

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