一种改进的基于BiDirectional体制的MISO-SAR系统

摘要

In 2012, the German Aerospace Center (DLR.) proposed a BiDirectional mode that can achieve several seconds of repeated time lags by single star and single flight. Its basic principle includes the generation of a double-beam antenna pattern by electronic beam steering and simultaneous emission of two pulses that irradiate the front and back imaging area. The two pulses, which are simultaneously received will be separated by band-pass filtering in the Doppler domain and imaged, respectively. This paper presents an improved Multi Input Single Output (MISO)-SAR system based on the BiDirectional mode which converts the traditional simultaneous dual beam emitting and receiving into time-division emitting and simultaneous receiving, respectively. This results in an improved emitting antenna pattern owning to the suppression of the Azimuth Ambiguity to Signal Ratio (AASR). The current paper describes the spectrum separation effects, AASR analysis, and the system design process. Therefore, to confirm effectiveness, point target 1-D and 2-D simulation results are compared before and after the improvement. Furthermore, the BiDirectional and other short-term repeated SAR modes are compared.%BiDirectional体制是德宇航在2012年提出的一种通过单星单次飞行实现秒级重访的新体制，基本原理是利用相控阵电扫描方式生成双波束天线方向图，同时发射两个脉冲照射方位向前后两块成像区域，将同时接收到的脉冲在多普勒域进行带通滤波分离，并分别成像。该文介绍了一种改进的基于BiDirectional体制的多发单收(Multi Input Single Output, MISO)SAR系统，将传统的双波束同发同收改进为分时先后发射和同时接收，利用发射时较优的方向图抑制方位模糊(AASR)，获得了较好的效果。文中给出了频谱分离效果、AASR分析和系统设计流程，给出了改进前后的点目标1维和2维成像结果对比，证明了该改进的有效性，最后给出了BiDirectional体制与其它几种单星短时重访体制的对比结果。