陕北地区典型地物背景与目标复合电磁散射研究

The echo of composite electromagnetic scattering from the background with target contains not only abundant information related to the land background but also rich information concerning characteristic information of shape, size, permittivity of target, etc. The study on characteristics of composite electromagnetic scattering from the background with target has important learning value and wide application prospect in the field of national defense and military and civil area. Due to the strong application demands on composite scattering characteristics, this project is devoted to the research on the physical nature and interaction mechanism between electromagnetic wave signal and land background with target by building the composite electromagnetic scattering model of land background with target. The calculation models of composite scattering from the typical land surface, such as soil surface and desert surface with target above or on it, as well as partially or fully buried targets in Northern Shaanxi region are built by utilizing spatial domain building method or fractal method. The time and space distribution features of the composite scattering field, the characteristics of angular distribution and the frequency response, the amplitude distribution and the fractal will be fully investigated in this project by using the numerical methods such as the Finite Difference Time Domain, Method of Moment as well as their parallel algorithms, based on the basic theory of composite scattering from random rough surface with target. This project will also explore the Doppler signatures, amplitude distribution, phase distribution as well as fractal characteristics of the composite scattering echo from moving target on or above the typical land surface, such as soil surface and desert surface in Northern Shaanxi region. On the basis of this project, an effective theoretical foundation can be provided for detection and recognition of target in natural land background.

背景与目标的复合散射回波不仅包含了丰富的地物背景信息，也包含了目标的形状、尺寸、介电常数等特征信息，研究背景与目标复合散射特性在国防军事和民用领域均具有重要的学术价值和广泛的应用前景。鉴于对复合散射特性的应用需求，本项目拟通过建立地物背景与目标的复合散射模型，研究电磁波信号与地物背景及目标之间的相互作用机理和物理本质；根据空间域合成法、分形方法等建立陕北地区土壤、沙漠等典型地物背景与其上方、置于其上、部分埋藏及埋藏目标复合散射的计算模型，基于粗糙面与目标复合散射的基本理论，应用时域有限差分方法、矩量法及其并行算法等数值方法得到复合散射场的时间、空间分布，复合散射系数的角分布特征，频率响应特征，幅值分布特征、分形特征；研究陕北地区土壤、沙漠等典型地物背景与运动目标复合散射回波的多普勒特征、幅值分布特征、相位分布特征、分形特征等。通过本项目研究，可为实际地物背景中目标的检测与识别提供理论支撑。

地物背景与目标的复合电磁散射特性研究在国防军事和民用领域均具有重要的学术价值和广泛的应用前景，当机载或星载雷达对处于地物背景中的军事或民用目标进行探测时，散射回波中包含了诸如地形起伏、地质构造、矿藏分布以及被探测目标的形状、位置、运行状态等信息，研究复合散射特性可为雷达目标探测与精确制导、地物表面遥感、地物表面附近目标的探测与识别提供必要的理论根据和有效的分析方法。.本项目主要研究土壤、沙漠等典型地物与目标复合散射模型的建立、复合散射系数的角分布特征特征。.本项目重要结果如下：.1.土壤表面与部分埋藏多目标复合散射：复合散射系数随散射角振荡变化; 土壤表面高度起伏均方根、土壤含水率、目标介电常数、入射角对复合散射系数影响较大; 土壤表面相关长度、目标截面宽度、高度、间距、倾角对复合散射系数影响较小;目标埋藏深度对复合散射系数几乎没有影响。.2.土壤表面与置于其上组合目标复合电磁散射：复合散射系数随散射角振荡地变化，在镜反射方向处发生散射增强效应；土壤表面高度起伏均方根越大，复合散射系数越大；相关长度越大，复合散射系数越小；湿度越大，复合散射系数越小；组合目标尺度、介电常数、入射角对复合散射系数影响比较复杂。.3.带限 Weierstrass-Mandelbrot 分形土壤表面与置于其上组合目标复合电磁散射：土壤表面高度起伏均方根越大，复合散射系数越大；分维越大，复合散射系数越大；湿度对复合散射系数影响虽小，但有固定的规律可循；组合目标尺度、介电常数、入射角对复合散射系数影响没有固定的规律可循；标度区间、空间基频对复合散射系数基本上没有影响。.4.横向沙丘表面电磁散射：沙丘坡顶高度、沙丘迎风坡坡底到坡顶的水平距离、沙丘坡顶间间距、入射角度和沙土湿度对散射系数的影响较大，而沙丘背风坡坡底到坡顶的水平距离对散射系数的影响较为复杂。.本项目揭示了电磁波与复杂目标/典型地物背景的相互作用机理和物理本质。