An Improved Parametric Polar Format Algorithm for Missile-Borne SAR Imaging With Large Squint Angles and Dive Trajectories

Abstract

Due to the complexity of the range model and the severe range-azimuth coupling in the signal echoes during the diving flight of missile-borne synthetic aperture radar (SAR), the traditional frequency-domain algorithms have the limitation of accuracy in the processing of missile-borne SAR imaging, and the complexity of the algorithm is relatively high. To solve the problem of mismatch between the algorithm and the range model in the diving state, an improved parametric polar format algorithm (PPFA) based on equivalent range model is proposed. First, this letter transforms the diving trajectory model of the missile-borne into an equivalent range model applicable to horizontal straight flight. Then, based on the equivalent range model, and considering the spatial variability of the equivalent velocity and squint angle, we improve the azimuth-focusing operation of PPFA. These enhancements resolve the issue of poor imaging effect of edge points by using traditional PPFA, significantly improving the edge point focusing performance. The effectiveness and feasibility of the proposed algorithm are verified by the experimental simulation results and various indexes.