A Video-SAR Imaging Technique for Aspect-Dependent Scattering in Wide Angle

Abstract

In a wide-angle synthetic aperture radar (SAR), as the isotropic scattering assumption becomes invalid, scattering characteristics of targets tend to be aspect-dependent. In this paper, based on the high center frequency characteristic of Video SAR (ViSAR), a ViSAR aspect-dependent scattering imaging algorithm (VADSIA) is proposed, which includes two main procedures of persistent polar format algorithm (PPFA) and generalized likelihood ratio test (GLRT). Through PPFA, sequential ViSAR sub-aperture images (sub-images) can be formed to the same orientation with the same image resolution efficiently, providing the advantage of easy extraction and display of the aspect-dependent scattering characteristic. Different from conventional algorithms that require 2-D aspect-dependent interpolation procedures, PPFA utilizes a uniform lookup table scheme and a 2-D Chirp-Z transform (2D-CZT) to realize persistent sub-aperture imaging. As PPFA includes only 2-D fast Fourier transforms and multiplications, it is suitable for parallel implementation to realize real-time imaging. Besides, with the persistent imaging ability of PPFA, an efficient approximate GLRT process can be applied on the formed sub-images directly, which can preserve both the aspect-dependent scattering characteristics and the azimuth resolution of targets at the same time. Combining PPFA with GLRT, VADSIA is an effective and efficient way for the aspect-dependent imaging. The ground-based experimental results validate the effectiveness of the proposed algorithm.