A deramp chirp scaling algorithm for processing spaceborne spotlight SAR data

Based on two-step algorithm and chirp scaling algorithm, a deramp chirp scaling (DCS) algorithm for processing high-resolution spaceborne spotlight synthetic aperture radar (SAR) data is presented. The algorithm combines the advantages of SPECAN algorithm and chirp scaling algorithm. Firstly, the azimuth coarse focusing is achieved via a deramp processing with constant Doppler rate, and the azimuth spectral folding phenomenon, which is typical for spaceborne spotlight SAR, was overcome. Secondly, the precise range focusing is achieved by chirp scaling principle, and the residual azimuth phase error is compensated, so the refined azimuth focusing is acquired. Based on the squinted equivalent range model that is fitter for spaceborne geometrical relation than the broadside range model, the complete derivation of the algorithm is presented and the realizing approach is given. Finally, the computer simulation shows the validity of the algorithm.