高分辨率星载聚束式SAR的 Deramp Chirp Scaling成像算法

基于两步处理算法和Chirp Scaling算法,提出一种适用于高分辨星载聚束式合成孔径雷达(SAR)的Deramp Chirp Scaling(DCS)算法.该算法结合了谱分析(SPECAN)算法和Chirp Scaling算法的优点,算法先采用具有固定多普勒调频率的deramp处理实现方位的粗聚焦,消除了星载聚束式SAR特有的方位频谱混迭现象,然后应用Chirp Scaling原理实现距离的精确聚焦,并补偿deramp处理引起的方位相位误差,实现方位精聚焦.基于斜视等效距离模型,该模型更好地拟合了星载聚束式SAR的空间几何关系,推导了DCS算法,给出了实现步骤,整个算法无需任何插值操作,只需复乘和FFT即可完成.该算法适用于宽测绘带高分辨率星载聚束式SAR的精确成像处理.最后,通过计算机仿真,验证了算法的有效性.

A Deramp Chirp Scaling Algorithm for High-Resolution Spaceborne Spotlight SAR Imaging

Based on Two Step processing approach and Chirp Scaling algorithm,a Deramp Chirp Scaling (DCS) algorithm for high resolution spaceborne spotlight synthetic aperture radar (SAR) imaging was presented.The algorithm combined the advantages of SPECAN algorithm and Chirp Scaling algorithm.Firstly,the azimuthal coarse focusing was achieved via a deramp processing with constant Doppler rate,and the azimuthal spectral folding phenomenon,which was typical for spaceborne spotlight SAR,was overcome.Secondly,the precise range focusing was achieved by Chirp Scaling principle,and the residual azimuth phase error was compensated,so the refined azimuthal focusing was acquired.Based on the squinted equivalent range model that was fitter for spaceborne geometrical relation than the broadside range model,the complete derivation of the algorithm was presented and the realizing approach was given.The whole algorithm could be implemented by complex multiplication and fast Fourier transform (FFT) without any interpolation of the data.The algorithm was suitable for wide range swath high resolution spaceborne spotlight SAR imaging.Finally,the computer simulation showed the validity of the algorithm.