Grating Lobe Suppression Method for Near-Field 2-D Sparse Distributed Aperture Radar

Distributed aperture radar (DAR) emulates an equivalent large-aperture performance by synthesizing multiple subarrays placed at different locations, offering a cost-effective solution for high-resolution radar systems. However, subarray spacing leads to spatially sparse sampling, resulting in grating lobes that degrade subsequent image interpretation. In this study, a near-field grating lobe suppression method based on subarray migration and spatial multi-apodization (MA) is proposed for non-uniform two-dimensional (2D) sparse DAR imaging. In our method, an optimized subarray response with sharp main lobe and low sidelobe level is achieved via parallel subarray migration and MA processing, which is further utilized to mitigate the prominent grating lobes arising from sparse inter-subarray placement. To address the spatial variation of array radiation characteristics under near-field effects, the proposed method is integrated into the back-projection algorithm (BPA) framework using an adaptive weighting strategy. Numerical experiments on extended targets demonstrate the superiority of the proposed method in grating lobe suppression, enabling high-fidelity, ambiguity-free near-field imaging with 2D sparse DAR systems.