Bistatic forward-looking SAR ground moving target detection and imaging

Bistatic forward-looking synthetic aperture radar (BFSAR) is a kind of bistatic SAR (BiSAR) system that can image the forward-looking terrain in the flight direction of a receiver. Current literature and reports about BFSAR imaging are mainly concentrated on stationary scene imaging. In this paper, the ground moving target (GMT) theories for BFSAR are discussed. Firstly, the BFSAR signal models of a general GMT in both time-domain and Doppler-domain are shown. Meanwhile, the echo characteristics of the GMT are analyzed, which include the migration characteristic, the Doppler characteristic, the coupling characteristic, etc. After the above analysis, a GMT detection and imaging method for BFSAR is presented. The main purpose of the GMT detection method is to find out the difference between the GMT and the stationary background in an appropriate domain. However, for BFSAR, it is hard to do this since the relative movements between the BFSAR sensors and the GMT are strongly coupled, i.e., their respective influences cannot be easily separated. Different from the existing detection methods which use Doppler frequency (Doppler centroid) in Doppler-domain or space-time characteristics in space-time domain to differentiate the GMT from stationary background, the main idea of the method proposed in this paper is to distinguish the GMT from stationary background by their different Doppler frequency rates (DFRs) in DFR-domain. However, in order to do this, the stationary background's DFRs must be equalized and the GMT's DFR should be distinct from the same DFR of the stationary background. Then, the product second-order ambiguity function (PSAF) is used to detect and focus the GMT. Numerical simulations and experimental data processing verify the validity of the GMT theories and the method shown in this paper.