A Modified Factorized Geometrical Autofocus Method for Wide Angle SAR

Wide-Angle (WA) synthetic aperture radar (SAR) has shown remarkable performance in high-resolution mapping, and its mostly used imaging algorithm, fast factorized back projection (FFBP), is efficient, robust, of low computational complexity. However, trajectory deviations the system calibration error, introduced by measurement accuracy, dramatically degrade FFBP's performance. This article proposes modified geometrical autofocus (MFGA) method for WA-SAR to address above problems FFBP. MFGA implements phase gradient algorithm on defocus subimages at first. Then, a error hypothesis between proposed. And corresponding factors are classified as three independent parts: image distortion, spectrum migration, error. To deal with those problems, introduces registration techniques maximum sharpness calibrate distortion Moreover, MFGA, based minimum entropy least square method, Doppler migration correction proposed correct migration. In FFBP chain, refocus fusion until obtaining full-resolution image. our experiments, we compared other time-domain algorithms using simulated data real obtained helicopter airship false parameters. The results show that performs better terms peak side-lobe ratio, azimuth resolution, refocused images' entropy, processing time consumption. demonstrates MFGA's advantages addressing WA-SAR.