Spaceborne Real Time DBF Processing Based on Multi-group Time Delayers

Digital beamforming （DBF） with multiple channels in elevation can obviously improve system performances of spaceborne high-resolution wide-swath synthetic aperture radar （HRWS SAR）. However， in the high resolution wide swath imaging mode， it is difficult to relieve the influence of pulse extension loss （PEL） for the conventional DBF processor， which leads to the performance deterioration. In this paper， according to the geometric model of spaceborne DBF Scan-On-Receive （SCORE）， the reason why targets far from the swath center are severely influenced by the PEL is analyzed. To solve this problem， a spaceborne real time DBF processing method based on multi-group time delayers is proposed. The time delayers in the conventional DBF processor are replaced by the multi-group time delayers to improve the system performances. Compared with the conventional DBF processor， the multi-group time delayers could provide more accurate time delay for all targets in the wide imaged swath， signals from all elevation channels can be better coherently combined， and the influence of PEL can be greatly relieved. Simulation results on point targets validate the proposed DBF processing method.