Multipath Exploitation: Non-Line-of-Sight Target Relocation in Array-InSAR Three-dimensional Imaging

With the development of synthetic aperture radar (SAR) three-dimensional (3D) imaging technology, urban 3D imaging has been realized by UAV-borne array-InSAR, which enables simpler access to SAR data. However, in low-altitude SAR 3D imaging of urban scenes, multipath effect is significant. In past studies, multipath signals have been mostly considered as a hindrance in interpretation, but they provide important clues for imaging hidden targets in non-line-of-sight (NLOS) regions. Based on this idea, this paper studies the multipath exploitation in low-altitude UAV-borne array-InSAR 3D imaging, and realizes accurate imaging of NLOS targets. An improved 3D imaging model suitable for low-altitude cases is introduced to achieve preliminary 3D imaging. Subsequently, key planes are extracted from the original results and the 3D multipath reachable area is analyzed. After obtaining the multipath mechanism of the NLOS targets, they can eventually be accurately relocated and imaged. Both the simulation and real-data experiments show that the proposed method can effectively 3D imaging and relocate NLOS targets in urban canyons, with errors typically below 0.5m. The imageable range in the direction of the ground range can be expanded by 41.62%, and the imageable 3D area can be expanded by 76.57%, which realizes the NLOS information acquisition.