机载TOPS模式两步成像算法研究

Research on two-step imaging algorithm for airborne TOPS mode

针对两步成像算法中传统预处理在计算残余多普勒带宽时没有考虑脉宽的影响,导致在对调频连续波大时宽信号进行处理时会产生误差的情况,首先从FMCW TOPS模式Dechirp接收回波信号模型出发,推导了两步成像算法预处理过程中去斜操作后回波数据残余多普勒带宽的解析表达式,并讨论了脉冲重复频率值设置方法;然后基于频率变标算法完成了对回波数据的距离压缩和距离徙动校正;最后通过方位变标和频域分析法消除了TOPS模式回波信号中存在的方位时域混叠,并实现了方位聚焦.通过仿真验证了本文所提出方法的有效性.

The influence of pulse width is not considered in the traditional preprocessing of two-step imaging algorithm in time of calculating the residual Doppler bandwidth,which leads to error in processing the FMCW signal with long time duration. In view of this problem, the paper starts from the dechirped echo signal model of FMCW TOPS mode, derives the analytical expression of residual Doppler bandwidth of echo signal after de-rotation in the preprocessing process of two-step imaging algorithm, and discusses the setting method of PRF value. Then,the paper is based on frequency scaling(FS) algorithm to complete the range compression and range migration correction of echo data. Finally, azimuth time domain aliasing in TOPS mode echo signal is eliminated by means of azimuth scaling and frequency domain analysis, with azimuth focusing achieved. The effectiveness of the proposed method is verified by simulation.