Efficient Rotating Synthetic Aperture Radar Imaging via Robust Sparse Array Synthesis

Rotating synthetic aperture radar (ROSAR) can generate a 360° image of its surrounding environment using the collected data from a single moving track. Due to its nonlinear track, the backprojection algorithm (BPA) is commonly used to generate SAR images in ROSAR. Despite its superior imaging performance, BPA suffers from high computation complexity, restricting its application in real-time systems. In this article, we propose an efficient imaging method based on robust sparse array synthesis (SAS). It first conducts range-dimension matched filtering, followed by azimuth-dimension matched filtering using a selected sparse aperture and filtering weights. The aperture and weights are computed offline in advance to ensure robustness to array manifold errors induced by the imperfect radar rotation. We introduce robust constraints on the main-lobe and sidelobe levels of filter design. The resultant robust SAS problem is a nonconvex optimization problem with quadratic constraints. An algorithm based on feasible point pursuit and successive convex approximation is devised to solve the optimization problem. Extensive simulation study and experimental evaluations using a real-world hardware platform demonstrate that the proposed algorithm can achieve image quality comparable to that of BPA, but with a substantial reduction in computational time up to 90%.