基于二维Chirp-Z变换的星载TOPSAR成像算法

Imaging Algorithm of Spaceborne TOPSAR Data Based on Two-dimension Chirp-Z Transform

TOPSAR是一种新型的星载SAR宽幅测绘模式。该模式成像算法需要解决三大问题:多普勒频谱混叠、较大的距离徙动和方位输出时间混叠。针对这些问题,该文提出了一种基于2维Chirp-Z变换的成像算法,给出了该算法的完整推导过程和各传递函数的表达式。其中,方位去斜预滤波处理能够在较少的方位总采样点数下解决多普勒频谱混叠;距离向和方位向Chirp-Z变换能够分别完成距离徙动校正和方位信号聚焦。由于该算法只需要在方位向上增加较少的采样点数,且不涉及任何插值操作,故其具有较高的运算效率。仿真数据处理结果验证了提出成像算法的有效性。

Terrain Observation by Progressive scans SAR（TOPSAR） is a novel spaceborne imaging mode with wide swath coverage.Imaging algorithms for such mode are required to resolve three existing problems： Doppler spectrum aliasing,large range cell migration and azimuth output time folding.As for these issue,a new imaging algorithm based on two-dimension Chirp-Z transform is proposed.The complete derivation processing of the presented algorithm and the expression of each transfer function are given in detail.In this algorithm,azimuth pre-filtering with deramp operation is adopted to resolve Doppler spectrum aliasing problem with fewer azimuth samples compared with other methods.Chirp-Z transforms in the range and azimuth domain can implement the large Range Cell Migration Correction（RCMC） and azimuth data focusing,respectively.The presented imaging algorithm only requires the limited azimuth increased samples and with interpolation free.Therefore,it is with high computational efficiency.Simulation results validate the effectiveness of the presented imaging algorithm.