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首页> 外文学位 >Study of electromagnetic scattering from randomly rough ocean-like surfaces using integral-equation-based numerical technique.
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Study of electromagnetic scattering from randomly rough ocean-like surfaces using integral-equation-based numerical technique.

机译：使用基于积分方程的数值技术研究随机粗糙海洋表面的电磁散射。

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摘要

A numerical study of electromagnetic scattering by one-dimensional perfectly conducting randomly rough surfaces with an ocean-like Pierson-Moskowitz spectrum is presented. Simulations are based on solving the Magnetic Field Integral Equation (MFIE) using the numerical technique called the Method of Ordered Multiple Interactions (MOMI). The study focuses on the application and validation of this integral equation-based technique to scattering at low grazing angles and considers other aspects of numerical simulations crucial to obtaining correct results in the demanding low grazing angle regime.;It was found that when the MFIE propagator matrix is used with zeros on its diagonal (as has often been the practice) the results appear to show an unexpected sensitivity to the sampling interval. This sensitivity is especially pronounced in the case of horizontal polarization and at low grazing angles. We show—both numerically and analytically—that the problem lies not with the particular numerical technique used (MOMI) but rather with how the MFIE is discretized. It is demonstrated that the inclusion of so-called “curvature terms” (terms that arise from a correct discretization procedure and are proportional to the second surface derivative) in the diagonal of the propagator matrix eliminates the problem completely. A criterion for the choice of the sampling interval used in discretizing the MFIE based on both electromagnetic wavelength and the surface spectral cutoff is established. The influence of the surface spectral cutoff value on the results of scattering simulations is investigated and a recommendation for the choice of this spectral cutoff for numerical simulation purposes is developed.;Also studied is the applicability of the tapered incident field at low grazing incidence angles. It is found that when a Gaussian-like taper with fixed beam waist is used there is a characteristic pattern (anomalous jump) in the calculated average backscattered cross section at incidence angles close to grazing that indicates a failure of this approximate (non-Maxwellian) taper. This effect is very pronounced for the horizontal polarization and is not observed for vertical polarization and the differences are explained. Some distinctive features associated with the taper failure are visible in the surface current (solution to the MFIE) as well. Based on these findings we are able to refine one of the previously proposed criteria that relate the taper waist to the angle of incidence and demonstrate its robustness.
机译：提出了一种具有海洋样皮尔森-莫斯科维兹光谱的一维完美传导随机粗糙表面电磁散射的数值研究。仿真是基于使用称为有序多重相互作用方法（MOMI）的数值技术求解磁场积分方程（MFIE）的基础上进行的。这项研究集中于这种基于积分方程的技术在低掠角处散射的应用和验证，并考虑了数值模拟的其他方面，这些条件对于在苛刻的低掠角条件下获得正确的结果至关重要。矩阵的对角线使用零（通常是这样），结果似乎显示出对采样间隔的意外敏感性。这种灵敏度在水平极化和低掠角的情况下尤其明显。我们从数字和分析方面都表明，问题不在于所使用的特定数字技术（MOMI），而在于MFIE的离散化方式。事实证明，在传播矩阵的对角线中包含所谓的“曲率项”（由正确的离散化程序产生并与第二表面导数成比例的项）可以完全消除该问题。建立了基于电磁波长和表面光谱截止值选择用于离散化MFIE的采样间隔的选择标准。研究了表面光谱截止值对散射模拟结果的影响，并提出了用于数值模拟目的选择该光谱截止的建议。还研究了锥入射场在低掠入射角下的适用性。已发现，当使用具有固定束腰的高斯型锥度时，在计算的平均后向散射截面中，在接近掠入射角的入射角处存在特征图案（异常跳变），表明这种近似失效（非麦克斯韦）锥度。该效应对于水平极化非常明显，而对于垂直极化则没有观察到，并且解释了差异。在表面电流（MFIE的解决方案）中也可以看到与锥度失效相关的一些独特特征。基于这些发现，我们能够完善先前提出的标准之一，该标准将锥形腰部与入射角相关联并证明其坚固性。

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  • 作者

    Toporkov, Jakov V.;

  • 作者单位

    Virginia Polytechnic Institute and State University.;

  • 授予单位 Virginia Polytechnic Institute and State University.;
  • 学科 Engineering Electronics and Electrical.;Physics Electricity and Magnetism.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 196 p.
  • 总页数 196
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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