基于去调频技术的斜视聚束SAR 成像方法

Abstract

This paper presents an imaging algorithm based on the deramp processing technique to resolve the imaging problem of the squinted spotlight synthetic aperture radar (SAR) in the presence of the azimuth spectrum folding phenomenon. First of all, we carried out the analysis of the azimuth spectrum folding phenomenon in squinted spotlight SAR, and found the reason for the squint angle impacts on the azimuth coarse focusing. Based on the analysis result, a nonlinear phase correction preprocessing method is introduced, which can completely remove the influence of the squint angle on the azimuth coarse focusing, and the correct coarse focused result is obtained. Then, based on the squinted SAR imaging model, the coarse focusing and precise focusing of the preprocessed echo data are deducted, respectively. In the azimuth matched filtering step of the precise focusing, a modified nonlinear chirp scaling (NLCS) algorithm is proposed for overcoming the azimuth depth of focus (ADOF) limitation problem, which is induced by the nonlinear phase correction preprocessing, and a high precise azimuth compression is achieved. Simulation experiment results prove the validity of the proposed algorithms.