Low-orbit Bistatic Frequency Modulated Continuous Wave SAR Imaging Method Based on Singular Value Decomposition

The imaging method of low-orbit bistatic SAR based on Frequency Modulated Continuous Wave (FMCW) signal is studied in this paper. The spaceborne bistatic model has the feature of transceiver separation and flexible structure. The nonlinear motion trajectory and bistatic slant range history are not conducive to the derivation and analysis of signal spectrum. The signal is constructed by a fourth-order polynomial slant range model. The expression of the two-dimensional spectrum of the signal is obtained by the method of series reversion. The spatial variation effect of the high-order polynomial coefficients is analyzed in detail. The range migration term is compensated in frequency domain. The azimuth phase is processed by the Singular Value Decomposition (SVD) method. Then the azimuth spectrum is divided into Doppler focusing terms and azimuth variation terms. A nonlinear azimuth scaling function is introduced. The azimuth variation can be completely corrected by two consecutive interpolations and resampling. The validity of the proposed method is verified by the simulation experiments.