OAM-based radar imaging of electrically large realistic targets using scattered echoes.

This paper investigates orbital angular momentum (OAM)-based radar imaging for electrically large realistic targets. Existing OAM imaging studies mainly focus on ideal point scatterers, while the imaging characteristics of realistic targets remain insufficiently explored. To address this gap, scattered echoes of electrically large realistic targets are computed by combining the angular spectrum decomposition method (ASDM) with the physical optics (PO) method, and OAM-based radar imaging is then studied using these echoes. By exploiting the approximate duality between the topological charge and the target's azimuth angle, one-dimensional angular-azimuth imaging is first analyzed. By further incorporating conventional radar imaging methods, two-dimensional range-angular-azimuth imaging, two-dimensional range-cross-range imaging, and three-dimensional image reconstruction are investigated. The polar format algorithm (PFA) with four-nearest-neighbor interpolation is employed to improve imaging quality. The effects of Bessel-function modulation and topological charge on image quality are examined, and the imaging behavior of typical targets, such as a blunt cone, is further analyzed under multiple viewing angles, different signal-to-noise ratios (SNRs), and target-position mismatch conditions. The results demonstrate that vortex waves show promise for target reconstruction while also revealing current limitations. This work therefore serves as a simulation-based bridge between point-scatterer OAM imaging models and realistic-target imaging based on scattered echoes, providing theoretical support for OAM-based radar detection.