High-Resolution Orbital Angular Momentum Imaging With the Removal of Bessel Function Modulation Effect

The vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has shown significant potential in high-resolution radar imaging. However, the Bessel function modulation (BFM) effect caused by the vortex wave's physical nature influences the imaging performance, especially under the limited OAM modes. To address this issue, we first establish a computationally efficient 2-D vortex radar imaging model and analyze the influence of the BFM effect on vortex radar imaging from the point spread function (PSF). Then, we propose a novel EM vortex radar imaging algorithm based on joint low-rank and sparse constrained representation. Specifically, the vortex radar echo data exhibits the inherent low-rank property, and hence a low-rank regularization term is introduced to remove the BFM effect. Moreover, a constraint corresponding to the image sparsity is adopted to eliminate the interference caused by the limited OAM modes. Hence, the high-resolution vortex radar imaging problem is modeled as a double-constrained underdetermined optimization problem. An iterative algorithm based on the alternating direction method of multipliers (ADMM) framework is further designed to solve the problem with high efficiency. Experimental results based on synthetic, EM, and measured data validate the effectiveness of the proposed algorithm.