半空间背景下目标电磁散射等效模型研究

在电磁场积分方程方法框架下,应用等效原理求解了半空间背景下目标的电磁散射问题,可针对目标仅处于半空间界面单侧及目标跨越半空间界面处于半空间两侧的几何相对位置。与传统的半空间格林函数计算方法不同的是,这一方法使用的是各自介质的自由空间格林函数,因此可以回避索墨菲积分并且可以很方便与快速算法(如多层快速多级子)相结合,并对求解临近半空间界面的目标获得较好的收敛性。在等效原理方法中需要用有限的界面等效无限大半空间界面,因此采用了锥形入射波以降低开放边界引起的边缘效应。不同于一般目标的远场雷达散射截面表达,在该模型下,半空间电磁散射的远场描述需要用差场雷达散射截面。给出的算例能与现有文献以及仿真软件很好的吻合,并可作为实用工具分析半空间背景对目标远场响应的影响。

Equivalent electromagnetic scattering model of target with half space background

Within the framework of integral equation method, a hybrid approach using equivalent principle is proposed to solve electromagnetic scattering problems. This theoretical model can resolve different relative position of target and the half space surface, including target at either side of the half space surface or the target straddling the surface. Apart from traditional methods using half space Green function to solve scattering problem concerning the existence of half space, the method in this paper uses free space Green function of the two dielectrics which form the half space. Therefore, Somerfield integral can be avoided and be compatible with fast algorithms (MLFMA etc.). Basic theory of equivalent principle is introduced. In this method, an infinite surface is truncated into a finite one, a therefore, tapered incident wave is used to avoid the edge effect. The far field response of a target with a half space background should be expressed as a differential radar cross section. Numerical examples show good agreement with the reference and simulation result from FEKO. The proposed method here can be a tool to analyze the effect of half space on the target nearby.