BiSAR Ground Moving Target Indication Method Based on Non-Uniform Subspace Projection

Background clutter and moving targets exhibit severe mutual aliasing in the space-frequency-range domain for BiSAR systems. Furthermore, due to the non-cooperative motion of targets, their imaging results often suffer from position displacement and defocusing, posing significant challenges for ground moving target indication (GMTI) tasks. To address these issues, this paper proposes a BiSAR-GMTI method via non-uniform subspace projection. Its core lies in revealing the intrinsic relationship and difference in the spatial steering vectors of clutter and moving targets between bistatic and monostatic SAR. By unifying their expressions, a non-uniform subspace that can effectively characterize the clutter distribution is constructed, thereby achieving background clutter suppression and precise moving target extraction. The specific implementation process consists of three steps: 1) The range-Doppler domain back-projection processing is employed to effectively compress the expansion influence of background clutter in the space-frequency-range domain. 2) The spatial steering vectors of clutter and moving targets in BiSAR systems are derived, based on which a clutter non-uniform subspace is constructed. Through subspace projection techniques, the moving target echoes are significantly enhanced. 3) A nonlinear mapping relationship between the moving target echo parameters and its motion state is established, and the Newton iteration method is applied to accurately solve for the target’s position and velocity parameters, achieving high-precision moving target indication. Simulation and flight experiment results validate the effectiveness and robustness of the proposed method.