基于deramp的星载聚束式SAR改进ECS算法

基于两步成像算法和ECS(Extended Chirp Scaling)成像算法,提出一种结合Deramp预处理的星载聚束式SAR(Synthetic Aperture Radar)改进的ECS成像算法.Deramp预处理是基于SPECAN算法的思想,将信号通过非空变的方位滤波器实现批压缩,该方法在保证成像分辨率的前提下,通过deramp处理消除了由采样率不足导致的方位频谱混叠特别是在星载SAR高分辨率聚束模式下.尽管ECS算法中的子孔径处理可以降低对系统脉冲重复频率的要求,但是脉冲重复频率依然受到单点多普勒带宽的限制.所介绍的方法可以进一步降低ECS算法中子孔径分割处理对脉冲重复频率的要求,使得ECS的算法的应用更为广泛.通过对点目标进行仿真和成像,成像指标评估验证了该算法的可行性.

Improved ECS algorithm for spaceborne spotlight SAR based on deramp processing

Based on the two-step imaging algorithm and the extended chirp scaling (ECS) algorithm,an approach for spotlight mode of spaceborne synthetic aperture radar(SAR), which combines the deramp processing and ECS algorithm was proposed. The deramp processing is based on SPECAN algorithm, and passes the raw data through a space invariant azimuth matched filter. The azimuthal spectral folding caused by insufficient sampling rate especially in high resolution spaceborne spotlight SAR was overcomed through the deramp processing. Although the division into subappertures in ECS can reduce the system requirement of the pulse repetition frequency(PRF), the PRF is restricted to higher than the accumulated doppler frequency bandwidth of a single point target. The presented method further reduces the requirement of the PRF in subapperture processing without the resolution loss. Thereby the ECS algotithm can be applied easily. The simulating and imaging results of point targets demonstrate the validity of this approach.