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 e ffect of DOA mismatch on echo separation. Extensive simulations that in comparison with the current DBF methods have been carried out to prove the e ffectiveness and prospect of the proposed CMRB DBF technique for airborne MIMO-SAR systems.