An improved scatter selection method for phase gradient autofocus algorithm in SAR/ISAR autofocus

The phase gradient autofocus (PGA) is a state of art technique for phase error correction of synthetic aperture radar (SAR) and inverse synthetic aperture radar (ISAR). It exploits the redundancy of phase error information among range bins by selecting the strongest scatter for each range bin and then synthesizes them. The motivation of this paper is based on the observation that the redundancy of phase error information is also among the cross-range (azimuth) direction in the image domain. A new scatter selection scheme is proposed to better utilize the phase error information contained in the image. The validity of our new prominent scatters selection method for PGA algorithm is theoretically analyzed and tested with some numeral simulation. It shows that a faster convergence speed can be obtained by our new method.