基于多次散射目标模型的雷达成像研究

合成孔径雷达（Synthetic Aperture Radar， SAR）作为一种主动微波传感器，被广泛应用于遥感对地观测。然而，传统上的雷达散射模型是基于几何光学近似的，忽略了地物目标之间的相互作用，即多次散射效应。为了充分挖掘和利用毫米波雷达影像中目标电磁散射特性信息，亟需对典型目标的多次散射效应进行建模仿真和验证。基于矩量法（Method of Moments， MoM）分析了球体、二面角等目标表面等效电流分布与分段成像结果的对应关系，并利用后向投影（Back-Projection， BP）算法进行电磁仿真成像，总结了单/双基地雷达模式对成像中散射机制的影响。结果表明：目标表面等效电流分布以及分段等效合成孔径张角会随入射角度发生改变，其中分段等效合成孔径张角会影响方位向分辨率；双基地雷达成像结果中包含更丰富的电磁散射信息。本研究可为SAR系统设计和验证、典型目标回波特性数据收集以及如何基于高解析度SAR影像进行目标识别等研究提供借鉴与参考。

Analysis of Radar Imaging based on Multiple Scattering Effect

As an active microwave sensor， the Synthetic Aperture Radar（SAR） is widely employed in earth observation. However， the traditional radar scattering model is based on geometrical optical approximation， which ignores the interaction among the ground objects， i.e.， the multiple scattering effects. To fully exploit and utilize the information of target electromagnetic scattering characteristics in millimeter-wave SAR images， it is imperative to simulate and verify the multiple scattering effects of typical targets. In this paper， the correspondence between the equivalent current distribution of the spherical surface and the dihedral angle and the segmentation imaging results was analyzed based on the Method Of Moments （MOM）， and the electromagnetic simulation imaging was performed by the Back-Projection （BP） algorithm. The effect of scattering on the single/bistatic mode radar imaging was summarized. The results show that the target surface equivalent current distribution and the segmental equivalent synthetic aperture angle change with the incident angle， and the segmented equivalent synthetic aperture angle affects the azimuth resolution. Moreover， it is found that the bistatic radar images include more abundant electromagnetic scattering information. These findings can provide reference for design and verification of SAR system， echo characteristic data collection of typical targets and identification of targets based on high-resolution SAR images.