Mirror-Based ArcSAR: Compact System Design and Azimuth Sidelobe Reduction for 360° Imaging of Complex Scenarios

Arc synthetic aperture radar (ArcSAR) employs a rotating arm to drive the antenna along a circular trajectory and thus achieves full azimuth imaging. However, ArcSAR implementation faces critical limitations in size- and efficiency-sensitive unmanned platforms, as the long rotating arm leads to large horizontal size and introduces centrifugal issues during rapid rotation. In this article, we propose a compact Mirror-based ArcSAR system that utilizes specular reflection to convert the physical rotation radius into a virtual one, thereby bringing benefits to reducing the system's horizontal size and alleviating instability during rapid rotation. Additionally, in order to suppress the high azimuth sidelobes, a back projection algorithm tailored for Mirror-based ArcSAR based on full-azimuth phase coherence factor (ArcBPA-FPCF) is introduced for full azimuth two-dimensional (2D) imaging. By employing azimuth coefficient and norm constraint of normalized range profile projection, ArcBPA-FPCF enables high-dynamic-range, 360$^\circ$2D imaging of surrounding areas with low additional computational burden. Examples from numerical simulation, indoor and outdoor measurement are presented to demonstrate the effectiveness of the proposed Mirror-based ArcSAR system and the performance of ArcBPA-FPCF in azimuth sidelobes suppression.