A back-projection fast autofocus algorithm based on minimum entropy for SAR imaging

This paper introduces an autofocus method for synthetic aperture radar (SAR) imaging. The algorithm is based on minimum entropy of the time domain back-projection (BP) technique. By dealing with the range compressed signal, we can get the azimuth focus result. For an ideal point target, through chooses the larger absolute value of the complex number pixels use BP algorithm to calculate the entropy for the complex image; on the other hand, for area target, we process a small part of the image which is the area we finally wanted. Computer simulation results for one point target and area target to prove the efficiency of this algorithm.