基于多路群时延的星载DBF实时处理方法
Spaceborne Real Time DBF Processing Based on Multi-group Time Delayers
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摘要: 距离向多通道数字波束形成(digital beamforming,DBF)技术可以显著提高星载高分辨率宽测绘带合成孔径雷达(high-resolution wide-swath synthetic aperture radar,HRWS-SAR)的系统性能,但在高分辨宽测绘带的情况下,传统DBF处理方法难以避免脉冲扩展损耗(pulse extension loss,PEL)的影响,导致DBF处理性能的显著下降。根据星载DBF扫描接收(Scan-On-Receive,SCORE)的几何模型,本文分析了离测绘带中心较远目标受PEL影响较大的原因。针对这个问题,提出了一种基于多路群时延的星载DBF实时处理方法,该方法将传统DBF处理中的单路群时延替换为多路群时延来提升DBF处理性能。与基于单路群时延的传统星载DBF处理相比,多路群时延处理方法可以为测绘带内的所有目标提供更精确的时延补偿,从而使得距离向各通道信号得到更好的相干合成,大幅度降低PEL的影响。点目标仿真结果验证了所提出星载DBF处理方法的有效性。Abstract: 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.