【作者】 程相哲；

【导师】 郭立新；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2010， 硕士

【摘要】 本论文就粗糙(地)面、植被表面电磁散射特性开展了系统的理论研究。利用常用的近似算法以及数值方法研究了一维、二维粗糙(地)面电磁散射,应用VRT方程和Monte-Carlo方法研究了双层植被模型的电磁散射特性,最后研究开发了有关地面和植被电磁散射的可视化软件。论文主要工作如下:1.在概述粗糙面相关统计概念基础上,应用Monte Carlo方法以及有限脉冲响应滤波器和快速Fourier变换相结合的方法模拟了一维、二维粗糙面。2.应用基尔霍夫近似(KA)算法对所模拟的一维、二维粗糙面模型的电磁散射特性进行了研究,分析了实际地面土壤的介电特性,并对实际地面散射系数的进行了求解。3.利用矩量法计算了一维导体/介质粗糙面的电磁散射,并进一步应用快速多极子方法对其求解,使其计算时间过长和占用资源过多的问题得以改善。将矩量法计算粗糙面电磁散射中常用的锥形波引入到传统的基尔霍夫近似中,同时考虑遮蔽效应,对传统的基尔霍夫近似进行修正,使其计算精度提高。4.在MIMICS森林模型的基础之上,建立了植被层和地面层组成的双层随机介质模型,应用矢量辐射输运理论(VRT)的零阶解和一阶解研究了双层植被的后向散射特性。同时考虑了实际粗糙地面植被模型的散射、增强效应,并应用Monte-Carlo进行了求解分析。5.根据上述章节的理论基础,结合实验室的电磁算法积累,在电磁仿真软件进行了尝试性的工作,设计开发了一款关于实际地面及植被电磁散射理论的可视化软件,为非从事电磁专业领域的工作人员提供了方便实用的软件系统。更多还原

【Abstract】 The dissertation presents systemic theoretical studies on the electromagnetic (EM) scattering by rough surface and vegetation. The approximate method and numerical method are applied to calculate the EM scattering from 1-D and 2-D rough surface. And the EM scattering of vegetation is investigated by the vector radiative transfer equation (VRT) and Monte-Carlo methods. Finally, we developed the visualization software on the EM scattering from the ground and vegetation. The main works are as follows:1. This paper begins by describing the rough surface of the relevant statistical concepts. The 1-D rough surface is simulated by the Monte Carlo method, and the 2-D rough surface is generated by the finite impulse response filter (FIR) theory combined with the fast Fourier transform (FFT) method.2. The electromagnetic scattering characteristic of` the 1-D and 2-D rough surface is studied by the Kirchhoff approximation (KA), and the dielectric properties of the actual land surface is analyzed, in addition, the scattering coefficient of the land surface is calculated.3. The method of moment (MOM) is adopted to compute the electromagnetic scattering of 1-D PEC and dielectric rough surface. The fast multipole method (FMM) is also presented to reduce the computation time and save the memory cost. The incident tapered plane wave in MOM method for scattering of rough surface is introduced into the classical KA method. Moreover, to obtain a high accuracy, the shadowing effect is also taken into account to modify the classical KA.4. Based on the Michigan Microwave Canopy Scattering (MIMICS) forest model, the two-layered random model composed of the vegetation and ground is established. The backscattering characteristic of two-layered vegetation is calculated by the zero-order and first-order solution of the VRT. And the backscattering enhancement of two-layered vegetation model is also analyzed by the Monte-Carlo method.5. Finally, according to the theoretical basis of the above-mentioned works, and the electromagnetic methods available in our laboratory, the visualized software on the electromagnetic scattering of the ground and vegetation is developed, which provides a convenient and practical software system for the non-professional staff engaged in electromagnetic fields.更多还原