An Improved Range-Doppler Imaging Algorithm Based on High-Order Range Model for Near-Field Panoramic Millimeter-Wave ArcSAR

The ground-based arc synthetic aperture radar (ArcSAR) can realize panoramic observation by utilizing the circular motion of the antenna. Since the circular trajectory of the antenna brings complicated high-order range-azimuth coupling in echo signal, far-field approximation (FFA), reference range approximation, or second-order series approximation to the range model are commonly applied for the conventional fast imaging algorithms to decouple the range-azimuth coupling. However, when a wide-beam millimeter-wave radar system is adopted to realize centimeter-level high-resolution imaging for near-field observation, these approximate treatments will cause severe defocusing in the image. In this article, an improved range-Doppler (RD) imaging algorithm is proposed. The high-order Taylor series approximation to the range model is adopted to meet the error requirement in the near-field wide-beam condition. By using the series inversion method, the analytical expressions for range migration and azimuth matched filter in RD domain are derived to achieve range-azimuth decoupling and precise azimuthal focusing within the whole range swath. Simulations and real-data experiments demonstrate that the proposed algorithm can achieve fast and accurate imaging, which can greatly support the millimeter-wave ArcSAR in near-field observation applications.