【作者】 张晓露；

【导师】 郭立新；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2009， 硕士

【摘要】 本文首先给出了粗糙面散射的基本理论,给出了随机粗糙面和沙丘的生成方法,介绍了粗糙面散射的基本方法基尔霍夫近似和微扰法;给出了沙漠的纵向沙丘和横向沙丘散射模型,推导了沙丘间多次散射的后向散射系数公式并分析了随波长、介电常数、高度均方根、相关长度和散射系数角分布的变化,与双尺度计算结果进行了比较。利用四成分模型计算了土壤湿度与土壤介电常数的关系,并分别用基尔霍夫近似法和微扰法计算了考虑不同土壤类型的电磁散射。基于基尔霍夫标量近似法和驻留相位近似法研究了粗糙面下方介质中的电磁透射和散射,导出了不同极化状态下指数谱粗糙面透射系数计算公式并进行了数值计算和讨论。最后利用微扰法计算了分层地面模型的一阶散射场,对其进行了详细讨论并与单层模型的散射系数进行了比较。更多还原

【Abstract】 In this thesis, fundamental theory of electromagnetic scattering from the rough surface is introduced for random rough surface models and electromagnetic scattering models, such as Kirchhoff Approximation and Small Perturbation Approximation. Models of longitudinal dune and transverse dune on the desert are presented. Backscattering coefficient of multiple scattering between dunes is derived. The influences of wavelength, dielectric constant, mean square root, correlation length and slope angular on the scattering coefficient from the rough surfaces with Exponential spectrum are analyzed, and numerical results are compared with Two-Scale Model for different desert models. According to the four-element model, the relation between humidity and dielectric constant of soil is presented and electromagnetic scattering from soil surface is calculated at different soils by Kirchhoff and Small Perturbation Method. Based on Scalar Approximation and Stationary-Phase Approximation, electromagnetic scattering and transmission in the medium under rough surface are investigated and formulae of transmission coefficients for different polarizations are presented and discussed numerically. The diagram of the scattering coefficient for different polarization transmission wave considering Exponential spectrum with varying of the scattering angle, the scattering azimuth angle and the frequency of the incident wave is obtained by numerical implementation. Finally, the first order electromagnetic scattering from layered model rough surfaces is also examined by applying the Small Perturbation Method and the comparison of scattering coefficients for the layered model and surface reflection are given and discussed in detail.更多还原