GSAT-Net: An Azimuth Ambiguity Suppression Network Based on Group Sparsity and Adaptive Threshold for Undersampling SAR Imaging

A pulse repetition frequency (PRF) below the Doppler bandwidth is pivotal in reducing the costs of data transmission and increasing the swath width for synthetic aperture radar (SAR). However, azimuth undersampling leads to severe azimuth ambiguity. Existing methods for azimuth ambiguity suppression do not perform adequately under downsampling rate. To overcome the shortcomings of existing methods, this letter proposes an efficient deep unfolding network that combines group sparse and adaptive threshold techniques for SAR imaging, named group sparse and adaptive threshold techniques for SAR imaging (GSAT-Net). In GSAT-Net, thresholds and sparsity are incorporated for both the main area and ambiguity areas, allowing for threshold shrinkage that is not only layer-varied but also element-wise. Finally, the effectiveness of the proposed method is verified by visual comparisons and numerical analysis.