Spaceborne spotlight SAR processing using the frequency-scaling algorithm

In this paper, the frequency scaling algorithm (FSA) has been introduced first to spaceborne spotlight SAR. According to the characteristics that the range time extension of the observed scene is smaller than the width of the transmitted pulse, FSA applied in airborne spotlight SAR dechirps on received echoes and reduces the sampling rate to release the computational burden. However in spaceborne SAR, the range extension is much larger and the bandwidth after dechirping increases instead so that the existing FSA cannot be adopted. To solve this problem, a method to perform directly frequency scaling on chirps in range direction has been proposed. And azimuth compression has also been applied to reduce PRF in azimuth direction. Finally, simulation results of point targets are given to demonstrate the validity and efficiency of the proposed algorithm.