星载TOPSAR方位变标成像算法

Processing of Spaceborne TOPSAR Data Using Azimuth Scaling

Burst工作模式和方位波束主动扫描使得TOPSAR回波信号同时存在多普勒频率混叠和方位输出时间混叠的问题.时域和频域同时升采样操作的"全孔径"方法虽然能够解决混叠问题,但同时带来成像运算量和内存消耗显著增加.根据星载TOPSAR回波特殊的方位时频关系,提出了一种结合方位变标操作的CS成像算法.方位变标操作可以避免"子孔径"分块和拼接操作,且更加有利于方位"锯齿状"天线方向图的补偿,同时该算法不需要进一步的方位时域扩展,从而大大提高了成像算法的效率.文中点目标和分布目标的仿真结果验证该算法的有效性.

Burst mode scheme and azimuth beam steering lead to the aliasing phenomenon of TOPSAR data existing in both the Doppler frequency and the azimuth output time domain.The ＂full-aperture＂ imaging approach with up-sampling operation in both azimuth time and frequency domain can overcome the aliasing problem.However,it brings an unwanted result of seriously increased computational complexity and memory consumption.Based on the special spaceborne TOPSAR raw data support in the slow time/frequency domain（TFD）,a new imaging approach combined with azimuth scaling operation and chirp scaling algorithm（CSA） is proposed in this paper.In this approach,sub-aperture formation and recombination are avoided and the sawtoothed azimuth antenna pattern correction can be easily implemented.As azimuth data extension in the output time domain in not required,efficiency of the presented algorithm is seriously improved.Simulation results of point and distributed targets validate the presented algorithm.