New algorithms for widefield SAR image formation

Abstract

The widefield polar format algorithm, the Stolt polar algorithm, and the differential Doppler algorithm use variations of a new along-track alignment and formatting system (ATAFS) to generate fine-resolution images from synthetic aperture radar (SAR) data. ATAFS introduces a spatially variant modification of the SAR phase history storage format to remove the formatting inaccuracies of the conventional polar format algorithm and enables full image quality over large scenes without range curvature distortion or image defocus. These new algorithms are well-suited for processing fine resolution spotlight and ultra-wideband SAR data. Their image quality performance is comparable to that of the range migration algorithm (RMA). Unlike RMA, the new algorithms operate on data stabilized to a fixed reference point to remove the azimuth chirp (the Doppler bandwidth of the reference point) before it compromises processor efficiency.