A Modified Nonlinear Chirp Scaling Algorithm for Highly Squinted SAR on Maneuvering Platform

Highly squinted synthetic aperture radar (HS-SAR) data focusing is a challenging task due to the heavy coupling between the range and azimuth, which would lead to the failure of the traditional imaging algorithms. In order to overcome these issues, a modified nonlinear chirp scaling (CS) algorithm for HS-SAR is proposed in this manuscript. First, traditional linear range walk correction (LRWC), range compressing (RC), secondary range compressing (SRC), range curvature correction (RCC) are employed as the range processing. Subsequently, a modulation phase factor (MPF) is introduced to weaken the influence of spatial variant (SV). After that, a high order SV correction phase (SVCP) approach is derived to eliminate the azimuth dependence of Doppler parameters. In addition, the sub-aperture data is focused on the range time and azimuth frequency domain by SPECAN processing to avoid numerous zeros-padding operations. Real data processing is adopted to prove the efficiency and validity of the proposed method.