A robust DBF method for Spaceborne SAR

It is well known that digital beamforming (DBF) is powerful technique to handle the conflict between high spatial resolutions and large swath width for Spaceborne SAR system based on multi-beam reflect-array antenna. The DBF technique can effectively suppress the interference (with different incoming elevation angle) caused by range ambiguity while maintain the gain on desired elevation direction. However, a performance degradation of the DBF will be occurred when geometry between the satellite and earth is uncertain. In this paper, the performance degradation caused by the uncertain geometry between the satellite and earth is analyzed. To overcome the performance degradation due to elevation angle mismatch, a robust DBF method for spaceborne SAR system is proposed. Our method can widen the null in receive beampattern to reduce the performance degradation due to angle mismatch.