An approach for improved processing in squint mode SAR

Processing SAR signal data into an image requires correlation with a range-variant focussing operator. Current SAR processing algorithms make approximations to the exact focussing operator, which causes a noticeable degradation in image quality when the squint angle is large. The difficulty arises from higher order phase terms in the operator known as secondary range compression (SRC). While recent approaches to high squint SAR processing allow accurate focussing for points at a fixed slant range, the range-variance of SRC has remained a problem. The approach presented in this paper is based on the chirp scaling technique, and accommodates the range-variance of SRC by modifying the phase modulation of the transmitted pulse