An effective focusing approach for azimuth invariant bistatic SAR processing

This paper proposes a processing method to extend monostatic imaging algorithms for the azimuth invariant bistatic SAR (BISAR) data where the transmitter and the receiver move on parallel tracks with equal velocities. The bistatic range history is approached by a polynomial of the azimuth time. Based on this model, an analytic 2-D signal spectrum derived by the method of series reversion is utilized and a simple one-to-one mapping between the transmitter and the receiver closest ranges is established. In this way, efficient monostatic imaging algorithms which operate in the 2-D frequency domain or the range-Doppler domain are easily modified to handle the BISAR data. In this paper, a chirp scaling algorithm for the BISAR is developed as an application of the new method. By implementing two key operations, range cell migration correction by a chirp scaling, and azimuth compression by a curve fitting technique, this algorithm is able to process the azimuth invariant BISAR data. Simulation results are presented to demonstrate the validity and the efficiency of the proposed algorithm.