A Robust Autofocus Algorithm for Stripmap SAR

Multi-subaperture autofocus algorithm is a commonly-used autofocus algorithm for processing stripmap SAR data. However, when the phase error is large, the performance of traditional multi-subaperture autofocus algorithms may decline. A robust multi-subaperture autofocus algorithm for stripmap SAR is proposed in this paper. This algorithm estimates the error in subapertures based on the minimum-entropy criterion first, and then use a "coarse to fine" method to estimate the shift amount of the error gradients. To speed up the algorithm, a variable-step-size search method is used. The real data processing verifies the feasibility and robustness of the algorithm.