Rotorcraft-Borne 3-D Forward-Looking MIMO SAR Imaging

This paper considers the three-dimensional (3-D) imaging problem for a rotorcraft-borne forward-looking multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) system. The conventional imaging methods, such as the back-projection (BP) algorithm, are computationally expensive, due to the large amount of data obtained from the two-dimensional (2-D) synthetic aperture. To address this problem, we introduce a two-step fast hybrid imaging algorithm, referred to as FHybrid, to enhance the computational efficiency of the conventional BP algorithm for 3-D MIMO SAR imaging. The proposed fast hybrid imaging algorithm combines the efficient pseudo-polar format imaging approach with the classical BP method. We also develop a relaxation-based imaging algorithm, referred to 3DRELAX for the 3-D forward-looking MIMO SAR imaging. FHybrid is used in the 3DRELAX iterations to improve the computational efficiency of 3DRELAX. The effectiveness and efficiency of the proposed imaging algorithms are demonstrated by using several numerical examples of targets at various ranges.