SNR Enhancement of Back Scattering Signals for Bistatic Radar Based on BeiDou GEO Satellites

Abstract

Using scattering signals of the global navigation satellite system (GNSS) for target detection has become one of the research hotspots. This technology faces the difficulty of low signal-to-noise ratio (SNR) target echoes. Since BeiDou geostationary orbit (GEO) satellites provide the opportunity to form a bistatic radar with some advantages, such as fixed coverage area and quasi monostatic configuration to avoid the interference from the direct signals, the target echoes may have regular phases that are beneficial to SNR enhancement. This study uses BeiDou GEO satellites and ground fixed receivers to form a bistatic radar and analyzes the phase changes in the reflected signal caused by the target, then gives two methods for SNR enhancement corresponding to two applications: deformation monitoring and ship detection. This paper first introduces the basic signal processing including the intermediate frequency (IF) signal collector and the range compression in the software receiver, then describes the basic SNR enhancement method, i.e., increasing coherence integration time (CIT), and shows its limitation by two target cases: static metal reflector on the land and ships in the water. After that, this study provides an improved SNR enhancement method based on Doppler and range compensation in the moving ship detection case. The experiment shows that by the SNR enhancement, the SNRs of target echo signals in range/Doppler domain increase more than 4 dB on average. This study also demonstrates the bistatic radar’s potential for monitoring surface deformation.

Moving Target Detection and Parameter Estimation Using BeiDou GEO Satellites-Based Passive Radar With Short-Time Integration

“…It is worth mentioning here that the envelope of the received signal in the azimuth-time dimension, which is related to the radiation pattern of receiving antenna, is neglected in our study. Furthermore, under the assumptions of the plane wave illumination and the second-order motion of the target, the expression of the IF signal after range compression can be found in Equation (11), which provides a basic formula for subsequent studies in this paper.…”

“…The index of the focused range cell stands for the distance between the receiver and the target, and the Doppler shift corresponds to the radial velocity of the target. During one coherent integration interval (CPI), if the target moves across multiple range gates, whose size depends on the sampling rate of the intermediate frequency (IF) signal and the signal bandwidth, the received energy from the target would smear to those cells [11]. The above phenomenon is known as Range Cell Migration (RCM).…”

SNR Improvement for Maneuvering Ship Using Weak Echo Under the Condition of Beidou GEO Satellites

“…When the raw data arrive in the RHCP and LHCP antennas, the intermediate frequency (IF) signal collector uses down conversion to record IF signals [19]. Afterward, the IF signals are processed using a software receiver to achieve range compression.…”

“…To verify the accuracy of the calculated parameters based on FrFT results, we give the acceleration calculated by range-Doppler (RD) processing [19]. Fig.…”

GNSS-Based Passive Inverse SAR Imaging

“…The main idea is to make use of GNSS reflected signals, which are considered as multipath interference in positioning application, to derive the geophysical parameters of the Earth's surface. Relevant topics include GNSS reflectometry (GNSS-R) [2][3][4][5][6][7], GNSS-based Synthetic Aperture Radar (SAR) [8][9][10][11] and SAR Interferometry (InSAR) [12,13], and GNSS-based passive radar [14][15][16][17][18][19][20][21], etc.…”