Mpga: modified phase gradient algorithm for spotlight sar filtered backprojection imagery

Phase gratitude algorithm (PGA) is a high-efficient autofocus technique that can estimate and compensate phase errors of SAR (synthetic aperture radar) imagery produced by frequency-domain algorithms. However, from conventional viewpoint, applying PGA on refocusing imagery produced by the time-domain algorithm, i.e., FBP, remains a huge challenge because the spectrum characteristics of FBP imagery are special. In this paper, a modified PGA (MPGA) for spotlight FBP (Filtered Backprojection) imagery is proposed, in which a spectrum correction is performed first to provide advantages for the standard PGA application. Simulations and real data experiments have been carried out to prove the effectiveness and prospect of the proposed approach for refocusing FBP imagery.