基于LFMCW体制的分布式SAR高分辨率成像方法研究

Signal Model and High-resolution Imaging Approach for Distributed SAR Based on LFMCW Signals

分布式微小卫星SAR是实现小型化、低成本星载SAR系统的重要途径,然而,在该体制下,如何充分利用分布式系统资源,实现高分辨率成像是其面临的关键问题之一。该文提出一种利用LFMCW信号实现分布式微小卫星平台SAR的方法,并基于方位向编队飞行的微小卫星构型,对其信号模型与高分辨率成像方法进行了研究。该文方法使用多颗微小卫星同时发射与接收频分LFMCW信号,利用交叉接收的构型使不同频带收发天线所形成的等效相位中心重合,进而在距离向对信号进行频带合成以恢复全带宽信号,从而实现高分辨率SAR成像。该方法实现了分布式平台信号的频带合成,为高分辨率LFMCW SAR技术在微小卫星平台上的应用提供了理论支撑。仿真实验验证了理论分析的正确性以及方法的有效性。

Distributed micro-satellites SAR has the capabilities of substantially miniaturizing the size and lowering the cost of space-borne SAR systems. However, one of the key issues is to take full advantage of the distributed resources and achieve high-resolution images. In this paper, an approach utilizing LFMCW signal is proposed to realize distributed micro-satellites SAR system. The signal model and the high-resolution imaging method is studied on the basis of the serial formation in azimuth. LFMCW signals are transmitted simultaneously and beat-frequency division signals are received by different micro-satellites. With the use of the crossed receiving technique, different sub-band signals with superposed equivalent phase centers can be acquired by the configuration design of formation flying, and then the full-bandwidth signal is synthesized to obtain high-resolution image. The proposed method synthesizes the sub-band signals of distributed platforms, which provides theoretical support for applying high-resolution LFMCW signals in the field of distributed micro-satellites SAR. The correctness of the theoretical derivations and the effectiveness of the approach is validated by simulation results.