大距离徙动情况下距离多普勒(RD)算法与后向投影(BP)算法的比较

Comparison of RD Algorithm and BP Algorithm Under Severe Range Migration

距离多普勒 (Range Doppler,RD)算法是传统窄带 /窄波束SAR的经典成像算法 ,它借助菲涅耳近似 ,只保留了斜距R(t)的线性部分和二次项。但是当距离徙动严重时 ,方位向二次以上的高次相位项不能忽略 ,这会大大降低聚焦精度。后向投影 (Back Projection ,BP)算法是一种基于时域处理的成像算法 ,通过计算双程延时将对应信号进行相干累加 ,获得高分辨率SAR图像。BP算法由于用时延代替了相位的概念 ,故与频率无关 ,不存在距离徙动校正的问题。本文介绍了RD算法和BP算法的原理及算法实现 ,并且利用距离向插值改进了BP算法。最后 ,结合计算机仿真结果详细比较了这两种算法的若干性能指标 。

Range-Doppler(RD)algorithm is a typical imaging algorithm for traditional narrow-band /narrow-beam SAR. It only keeps the linear part and the quadratic term of the slant range distance by using Fresnel approximation. However, the high-order parts of azimuth phase cannot be ignored when range migration is large, which would worsen focusing precision greatly. Back-Projection (BP) algorithm based on time-domain processing, can attain high-resolution SAR image by calculating the two-way propagation delay time and coherently summing up the corresponding signals. BP algorithm replaces the concept of phase with delay time, so it is irrelevant to frequency and the problem of range migration correction does not exist. This paper introduces basic theory and implementation of RD algorithm and BP algorithm, and improves BP algorithm through range interpolation. Comparison of the performance of two algorithms with the computer simulation results proves that BP algorithm is more suitable than RD algorithm for SAR imaging under severe range migration.