Robust Anti-Topography-Variation Beamforming Technique for Airborne MIMO-SAR Echo Separation

The echo separation problem in the application of multiple-input multiple-output (MIMO) concept on synthetic aperture radar (SAR) systems is considered as a more technical challenge. It has been shown that the separation of aliased signal returns can be achieved by the state-of-the-art elevation beamforming techniques, e.g., the well-known short-term shift-orthogonal (STSO) scheme. However, the directions of arrival (DOAs) of the signal segments are usually inaccurate due to the unknown topography variation, especially for airborne MIMO-SAR systems. The DOA mismatch can seriously deteriorate the digital beamforming (DBF) performance of STSO scheme. To this end, a covariance-matrix-reconstruction-based (CMRB) robust beamforming technique is introduced in our paper to alleviate the effect of DOA mismatch on echo separation. Extensive simulations that in comparison with the current DBF methods have been carried out to prove the effectiveness and prospect of the proposed CMRB DBF technique for airborne MIMO-SAR systems.