Nonlinear FM frequency scaling method for processing squint mode spotlight SAR

This paper presents a method for squint mode spotlight SAR imaging. The method bases on the frequency scaling algorithm (FSA) and improves imaging quality of targets far away from scene center in range. For applying to squint mode, the dechirp function and some compensation functions of the FSA are modified. In this paper, unfocused imaging within both sides of range swath in the case of larger range swath and squint mode are analyzed particularly. The nonlinear FM filtering method is combined with the frequency scaling operation to obtain exactly focused image. Simulation results of point targets are given to show the improvement of and demonstrate the validity of the proposed algorithm.