随机粗糙面光散射的后向增强效应研究

发布时间：2018-03-08 06:00

本文选题：粗糙面　切入点：后向增强　出处：《西安电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：后向增强现象是粗糙面电磁散射中非常重要的特性,它是指非相干散射分量在后向散射方向上出现峰值的现象,后向增强现象蕴含目标以及背景方面的很多信息,在微波,红外以及可见光遥感和雷达目标探测领域均有着重要的应用。由于光频段金属的介电特性呈现特殊性质,即相对介电常数为复数,且实部为负,实部的绝对值远大于虚部,因此研究光波段金属粗糙面的散射特性有着重要意义。本文主要围绕大粗糙度粗糙面和微粗糙金属粗糙面光散射的后向增强效应展开讨论。本文首先介绍了适用于大粗糙度粗糙面电磁散射的二阶基尔霍夫近似理论,并给出了考虑遮蔽效应的一阶、二阶基尔霍夫近似下非相干散射的散射截面表达式,分别计算和比较了光波段下金属粗糙面和介质粗糙面的非相干散射散射截面的角分布。论证了大粗糙度粗糙面光散射的后向增强效应是由于电磁波在粗糙面之间的多次散射造成的。本文重点研究微粗糙金属粗糙面光散射的后向增强效应。首先,论述了微粗糙金属粗糙面光散射后向增强效应的物理机制——表面等离子体激元(SPPs)机制,并给出了SPPs的色散关系。利用退化的瑞利方程和微扰方法分别计算了光波段下一维高斯谱、矩形谱金属粗糙面和二维高斯谱、圆柱谱金属粗糙面的非相干散射的平均微分反射系数的角分布。计算结果表明只有当入射光是TM极化时一维微粗糙金属表面才会激发SPPs,造成非相干散射平均微分反射系数的后向增强,而光入射到二维微粗糙金属表面时,四种极化方式都会出现不同程度的后向增强。同时分析了入射角、粗糙面粗糙度和粗糙面介电常数等对后向增强的影响。最后,本文研究了金属薄层和理想导体涂覆介质薄层表面光散射的特性,除了后向的增强还会存在“伴峰”现象,利用色散关系求解了薄层中导波的波数与薄层厚度的关系,并给出了散射角分布“伴峰”的位置与导波波数的关系。利用分层结构中电磁散射的微扰理论分别计算了金属薄层和理想导体涂覆介质薄层表面光散射的平均微分反射系数的角分布。重点讨论了薄层厚度对“伴峰”位置以及“伴峰”强度的影响,分析了入射角、薄层厚度以及介质薄层介电常数等对后向增强的影响。
[Abstract]:Backward enhancement is a very important characteristic of electromagnetic scattering from rough surface. It refers to the phenomenon that the incoherent scattering component has peak value in the direction of backscattering. The phenomenon of backward enhancement contains a lot of information about the target and background. Infrared, visible remote sensing and radar target detection have important applications. Because of the special dielectric properties of metals in the optical band, that is, the relative dielectric constant is complex, and the real part is negative, the absolute value of the real part is much larger than that of the imaginary part. Therefore, it is of great significance to study the scattering characteristics of metal rough surfaces in light wave region. This paper mainly discusses the backward enhancement effect of light scattering from large roughness rough surfaces and micro-rough metal rough surfaces. The Second-Order Kirchhoff approximation Theory of electromagnetic scattering on rough Surface with large Roughness. The first order, second order Kirchhoff approximation is also given for the expression of the scattering cross section of incoherent scattering in the first order and the second order Kirchhoff approximation. The angular distributions of incoherent scattering cross sections of metal rough surface and medium rough surface are calculated and compared, respectively. It is proved that the backstepping effect of light scattering from large roughness rough surface is due to the electromagnetic wave between rough surfaces. In this paper, we focus on the backward enhancement effect of light scattering from micro-rough metal rough surfaces. In this paper, the physical mechanism of backscattering enhancement effect of light scattering from rough surface of micro-rough metal, surface plasmon excitation (SPPs) mechanism, is discussed. The dispersion relation of SPPs is given. Using the degenerate Rayleigh equation and perturbation method, the one-dimensional Gao Si spectrum, the rectangular spectrum, the metal rough surface and the two-dimensional Gao Si spectrum are calculated, respectively. Angular distribution of the average differential reflection coefficient of incoherent scattering from a cylindrical spectrum metal rough surface. The calculated results show that only when the incident light is TM polarized can the SPPs be excited on the surface of the one-dimensional micro-rough metal, resulting in the average differential of incoherent scattering. Backward enhancement of the reflection coefficient, However, when the light is incident to the two-dimensional micro-rough metal surface, the four polarization modes will show different degrees of backward enhancement. At the same time, the influence of incident angle, roughness of rough surface and permittivity of rough surface on the backward enhancement is analyzed. In this paper, the surface light scattering characteristics of metal thin layer and ideal conductor coated dielectric thin layer are studied. In addition to the backward enhancement, the phenomenon of "accompanying peak" also exists. The relationship between the number of guided waves and the thickness of the thin layer is solved by using the dispersion relation. The relationship between the position of the scattering angle distribution "accompanying peak" and the guided wave number is also given. The average micro-scattering on the surface of metal thin layer and ideal conductor coated dielectric thin layer is calculated by using the perturbation theory of electromagnetic scattering in stratified structure. The influence of the thickness of thin layer on the position and intensity of the "companion peak" is discussed. The effects of incident angle, thickness of thin layer and dielectric constant of dielectric thin layer on backward enhancement are analyzed.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN011

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