Focusing High-Resolution High Forward-Looking Bistatic SAR With Nonequal Platform Velocities Based on Keystone Transform and Modified Nonlinear Chirp Scaling Algorithm

This paper presents a focusing solution for high-resolution high forward-looking bistatic synthetic aperture radar with nonequal platform velocities (NPV-BFSAR). In NPV-BFSAR, due to the high-resolution SAR and high forward-looking angle, range cell migration, and two-dimensional spatial variation are more serious. To solve this problem, a modified imaging algorithm based on second-order keystone transform (KT) and modified nonlinear chirp scaling (NLCS) method are proposed. The second-order KT method can correct the linear range cell migration and reduce the strong coupling between azimuth and range. The proposed modified azimuth NLCS algorithm is more accurate than traditional NLCS algorithm on eliminating the variation of azimuth reference function that can improve the focus quality of edge targets. Finally, some simulation results confirm the efficiency of the proposed algorithm.