平地假设对合成孔径雷达时域算法成像质量的影响研究

摘要

Time-domain algorithms have great application prospect in Ultra Wide Band Synthetic Aperture Radar (UWB SAR) imaging for its advantages such as perfect focusing and perfect motion compensation. We could adopt the flat surface assumption to simplify the imaging geometric model, when undulating terrain is imaged using time-domain algorithms. Nevertheless, the flat surface assumption leads to geometric errors, thereby affecting the imaging results. This paper studies the effects of this assumption on time-domain imaging algorithms, points out that it leads to position offset problem in the case of linear aperture, and it even leads to target defocusing problem in the case of non-linear aperture. The expression of position offset is given in this paper, as well as the restriction of the maximal offset of the non-linear aperture and the maximum elevation of the area in order to focus the targets. The conclusions are validated by simulated data, which is processed by one kind of time-domain algorithms, namely Back Projection (BP) algorithm.%　　时域算法具有精确成像和易于运动补偿等突出优点,在超宽带合成孔径雷达(Ultra Wide Band Synthetic Aperture Radar, UWB SAR)成像领域应用前景广阔。当使用时域成像算法对起伏地形成像时,可引入平地假设来简化成像几何模型,但平地假设会引入几何误差,进而影响成像质量。该文研究了平地假设对时域算法成像质量的影响,指出其影响在直线孔径条件下表现为位置偏移,在非直线孔径条件下还将造成目标散焦。同时推导得到了目标位置偏移量的表达式,给出了目标聚焦时非直线孔径最大偏移和地表高程起伏程度应满足的定量条件。最后采用时域算法中的后向投影(Back Projection, BP)算法处理仿真数据,处理结果验证了该文相关结论。