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.
Highlights
The results show that when coherent integration time (CIT) = 50 ms, CAP is efficient for pontoons A and B, and the correlation peaks of reflected signals are visible
15a, the signal-to-noise ratio (SNR) of the reflected signal from cargo ship C is 6.1 dB, which is confused with the surrounding interference signal
We study SNR enhancement algorithm and applications of reflected signals under the condition of a bistatic radar system consisting of BeiDou geostationary orbit (GEO) satellites and a fixed receiver
Summary
Using global navigation satellite system (GNSS) reflected signals to construct a bistatic radar for remote sensing on an object is a popular issue. When the radio signal transmitted from the navigation satellite impinges on the target, it is reflected and contains the target information, a satellite-based, aircraft-based, or ground-based receiver is employed to capture this signal and retrieve the physical parameters such as vegetation optical depth, soil moisture, sea ice surface, and ocean surface wind speed [1,2]. When the receiver is installed at a fixed position on the ground, the receiver can be used for target imaging [3,4,5,6], maritime target detection [7,8], and surface deformation monitoring [9,10]
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