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特性仿真及分析

为了满足置于粗糙面之上组合目标雷达回波特性的数据采集、特征提取的需要，采用Topp模型和电介质复介电常数计算公式模拟土壤介电常数的实部和虚部，应用带限Weierstrass-Mandelbrot分形函数模拟土壤表面，运用时域有限差分方法研究了带限Weierstrass-Mandelbrot分形土壤表面与置于其上组合目标的复合散射，并仿真了复合散射系数的角分布曲线。仿真结果表明，复合散射系数随散射角振荡地变化，在镜反射方向处产生散射增强效应；土壤表面高度起伏均方根越大，复合散射系数越大；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。

Characteristics of composite electromagnetic scattering from band limited Weierstrass-Mandelbrot fractal soil surface and combinatorial targets placed on it

In order to meet the needs of data acquisition, feature extraction of radar echo characteristics of combinatorial target placed on the rough surface, Topp model and dielectric complex permittivity calculation formula are used to simulate the real and imaginary parts of the soil dielectric parameter, the soil surface is simulated with the Weierstrass-Mandelbrot fractal function, the electromagnetic scattering from the composite model consisting of soil surface and combinatorial target placed on it is studied by the finite-difference time-domain method, and the angle distribution curve of composite scattering coefficient is simulated. The simulation results show that the composite scattering coefficient oscillates with the scattering angle, and the scattering enhancement effect occurs in the mirror reflection direction; the larger the root mean square of the fluctuation of soil surface, the larger the composite scattering coefficient; the larger the fractal dimension, the larger the composite scattering coefficient; although the influence of the soil moisture content on the composite scattering coefficient is small, there are fixed rules to follow; there is no fixed rule for the influence of the scale and dielectric constant of combinatorial target, incident angle on the composite scattering coefficient; scale interval and spatial fundamental frequency have no effect on the composite scattering coefficient.