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An autofocus method was presented based on an entropy criterion for synthetic aperture radar imaging. An iterative method, through minimizing the entropy, was derived to obtain the phase error which corrupted the image and increases image entropy. Moreover, dominant scatterers were selected as the input of the phase-error estimation, which was similar to the phase gradient autofocus algorithm. There were not any model assumptions for the phase error in the proposed method. Phase estimation accuracy was also analyzed. Finally, the simulation and experimental results were utilized to validate the feasibility and effectiveness of the proposed method.
Zeng et al. (Tue,) studied this question.