Highly Squint Airborne SAR Real-time Imaging

A highly squint airborne SAR real-time imaging algorithm named the extended CS algorithm is introduced in the paper. Some important approximations of the classic CS algorithm are analyzed and the analyzed method is valuable for the selection of imaging algorithm for a SAR system. As the squint angle becomes larger, the approximation error will be unacceptable and the algorithm should be modified. The presented extended CS algorithm adds phase information to compensate the cubic term of the range frequency Taylor expansion of the signal phase in the two-dimensional frequency domain which is ignored by the classic CS algorithm. In the classic CS, the effective chirp rate at any range is approximated to its counterpart at the reference range. The approximation error may become unacceptable as the range size of the scene is large, which can be resolved by dividing the scene into several partitions and respectively processing them. The validity of highly squint airborne SAR data imaging system is proved by the imaging results