Abstract: If the scatter selected in phase gradient algorithm (PGA) algorithm is not isolated, the accuracy of the phase error estimation will be degraded. In this paper some modifications to the dominant scatter selection method are proposed, and then an improved PGA solution based on adaptive isolated scatter selection is presented. First, the quality of each pixel in the image is evaluated by a sliding window in the azimuth direction, and then the high quality scatters are selected for the phase error estimation, followed by multiple dominant scatters synthesis with the value of quality evaluated in order to improve the accuracy of the phase error estimation. Analysis and the results of real data processing show that the improved PGA algorithm outperforms the original one especially for the scene in which the bright scatters are not isolated.

Key words: synthetic aperture radar, phase gradient algorithm, autofocus, radar imaging