基于载机运动特征的FMCW SAR前视成像仿真分析

Simulation Analysis of Forward-Looking FMCW SAR Imaging Based on Aircraft Motion Characteristic

基于阵列技术的机载前视线性调频连续波(FMCW)合成孔径雷达(SAR)能对载机前方区域高分辨成像,且能满足机载SAR小型化的需要。针对前视成像若不考虑载机运动时信号模型不完整和系统应用受到制约的问题,提出基于载机运动特征的FMCW SAR前视成像。分析了前视FMCW SAR与脉冲SAR信号收发模式等问题的异同,建立了基于载机运动特征的前视FMCW SAR信号模型。分析了载机运动的影响,并重点讨论了载机运动引入的多普勒频率偏移。结合距离-多普勒(RD)算法流程给出了多普勒频率偏移的补偿方法并进行了仿真研究。结果表明,载机运动会引起点目标航线向主瓣展宽、旁瓣畸变以及目标位置的搬移,通过补偿可有效消除载机运动的影响。

Airborne forward-looking Frequency Modulated Continuous Wave （FMCW） Synthetic Aperture Radar （SAR） based on array technology could supply high-resolution images of the area with respect to forward direction of the flight path and meet the need of miniaturization for airborne SAR. To solve the problem that aircraft velocity was ignored for forward-looking SAR, which caused non-intactness of signal model and application limitation, forward-looking imaging of FMCW SAR based on aircraft motion characteristic was proposed. Similarities and differences between forward-looking FMCW SAR and pulse SAR, such as signal transmit-receive mode etc., were discussed. Signal model of forward-looking FMCW SAR based on aircraft motion characteristic was established. Effect of aircraft motion was analyzed and . Doppler frequency shift resulted from continuous motion of aircraft was discussed with emphasis. Method of Doppler frequency shift compensation was given combined with Range-Doppler （RD） algorithm and simulation was made. Results indicate that continuous motion of aircraft can cause main-lobe extension, side-lobe aberration and position variation, which can be eliminated by compensation effectively.