Chirp Scaling算法中的相位补偿因子研究
doi: 10.3724/SP.J.1146.2005.00634
Research on Phase Compensating Factors in Chirp Scaling Algorithm
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摘要: 该文从SAR回波的二维频谱表达式入手，研究了适合高波段SAR的CS(Chirp Scaling)类算法和一种适合超宽带(Ultra Wideband，UWB)SAR成像的非线性CS算法，通过对算法推导中的近似性分析，重新刻画了SAR成像，即SAR成像是利用回波频谱特性构造频域或时域相位补偿因子的过程，尤其是对UWB SAR回波，相位补偿因子的精确性直接影响着目标聚焦性能。仿真实验表明，补偿三阶以上二维相位耦合的非线性CS算法能够在一定的测绘带内满足UWB SAR点目标的理想聚焦；同时，该算法在UWB SAR实测数据处理中也已得到成功应用。Abstract: In this paper the two-dimensional frequency expression of SAR echoes are first analyzed. Then, the standard chirp scaling algorithm and its several modified forms used both in high frequency narrow band SAR and low frequency Ultra WideBand (UWB) SAR are compared in a united frame of two-dimensional frequency expression. The approximations made by different algorithms are evaluated in detail. So a new depiction for SAR image formation is proposed, which is a process of constructing phase compensating factors in frequency or time domain according to the characteristics of echo spectrum. Especially, the accuracy of phase compensating factors for UWB SAR echoes has a direct impact on point targets focusing. Simulation results verify that the modified non-linear chirp scaling algorithm, which can compensate the more third orders phase coupling, can arrive an ideal focusing UWB SAR image in the certain of scope. Further more, the algorithm has been used successfully in raw UWB SAR data processing.
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