A beam segmentation based 2-step polar format algorithm for highly squinted SAR

In high squint and high resolution SAR, one key technique is the large Range Cell Migration (RCM) correction method. As the resolution gets higher and the squint angle gets larger, the RCM of one point target might extend 10,000 range bins in the whole aperture. An appropriate algorithm fit for squint mode is acquired with very high precision to accurately correct the severe range migration. In this paper, a new digital spotlighting preprocessing based 2-step PFA method is proposed. The method performs beam segmentation via digital spotlighting preprocessing firstly to generate multiple full-resolution phase histories of smaller image patches, which allow the approximation of planar wavefront in traditional PFA. PFA is used to produce focused fine resolution image for each small patch. Finally, all focused image patches are seamed together to get a full image. This divide-and-conquer approach breaks the image size limit in traditional PFA, extensively enlarge the valid focused scene. This new algorithm is validated effective and efficient via real data experiments.