Adaptive imaging of anisotropic target based on circular‐SAR

Abstract

The isotropic reflectivity assumption is a valid approximation in traditional narrow-angle synthetic aperture radar (SAR). However, for large angular ranges most targets exhibit only limited scattering persistence. Therefore, this assumption is violated in circular-SAR (CSAR). Thus, the performance of traditional fully coherent image formation is poor in CSAR, because coherent integration over the entire aperture will obscure aspect-independent reflectivity characteristics. To address this problem, an adaptive imaging algorithm which accommodates anisotropic targets to improve image quality is proposed. The efficient use of valid azimuth angles can reduce noise and errors and highlight anisotropic targets in CSAR image. Another advantage of this algorithm is that the anisotropy target scattering behaviour can be extracted by data inversion in the imaging process. Compared with the sub-aperture approach, which can also extract the anisotropic scattering properties of target, the data inversion approach in the algorithm can provide more accurate results and a finer curve. The adaptive imaging method is validated in this Letter by simulation and an airborne dataset.