基于微面斜率法的粗糙表面半透明介质层光谱散射特性分析

对具有一维高斯分布粗糙表面的半透明介质层光谱散射,基于微面斜率法建立了考虑遮蔽效应的粗糙表面光谱辐射传递概率模型,采用蒙特卡罗法模拟光谱辐射能束在粗糙表面、半透明介质层介质与镜反射基底之间的多次反射、折射和吸收等传递过程。通过数值模拟,分析了介质层表面粗糙度、光谱光学厚度、折射率和基底反射率对介质层双向反射分布函数(BRDF)的影响。结果表明,表面粗糙程度不同时,反射峰值随入射角度呈现不同的变化趋势;表面粗糙度增加或折射率增大都将导致漫反射份额增大;介质层光谱光学厚度和基底反射率主要影响BRDF的数值大小,而对BRDF的分布形态影响很小。     

随机粗糙表面光散射场分布特性的机理研究

为了研究随机粗糙表面光散射分布特性机理,采用线性滤波法生成高斯分布随机粗糙表面,以基尔霍夫近似作为电磁场边界条件,采用蒙特卡罗方法数值计算了一组金属和一组电介质粗糙表面在S偏振光和P偏振光照射下的散射光强度空间分布。计算结果显示:金属表面与电介质表面的散射光分布宽度、散射峰值、散射峰位置三个散射特征存在显著差异,经过分析发现这种特征差异的产生机理是由表面面元的斜率分布和面元反射率共同因素导致,与数值计算结果对比,二者具有良好的一致性。     

大尺度分层介质粗糙面电磁散射的特性研究

首先建立大尺度分层介质粗糙面散射的物理模型, 基于Stratton-Chu积分方程和Kirchhoff近似导出了粗糙面散射场的计算公式. 采用高斯随机粗糙面来模拟实际的分层介质粗糙面, 通过数值计算得到了正下视单站雷达接收到的后向散射回波. 理论推导了散射场强度与表面粗糙度之间的定量关系, 并从数值仿真的角度分析了表面和次表面的粗糙度对散射回波的影响, 给出了散射场随粗糙度变化的曲线. 最后考察了分层介质的电特性参数(介电常数和电导率)对分层粗糙面散射场的影响, 并对计算结果做出了分析.     

SiC/SiO2界面粗糙散射对沟道迁移率影响的Monte Carlo研究

提出了一种SiC反型层表面粗糙散射的指数模型,并对6H-SiC反型层迁移率进行了单电子的Monte Carlo模拟,模拟中考虑了沟道区的量子化效应.模拟结果表明,采用表面粗糙散射的指数模型能够使SiC反型层迁移率的模拟结果和实验值符合得更好.模拟结果还反映出有效横向电场较高时表面粗糙散射的作用会变得更显著,电子的屏蔽效应降低了粗糙散射对沟道迁移率的影响,温度升高会引起沟道迁移率降低. 关键词： 6H-SiC 反型层迁移率 表面粗糙散射 指数模型     

SiC/SiO_2界面粗糙散射对沟道迁移率影响的Monte Carlo研究

提出了一种SiC反型层表面粗糙散射的指数模型 ,并对 6H SiC反型层迁移率进行了单电子的MonteCarlo模拟 ,模拟中考虑了沟道区的量子化效应 .模拟结果表明 ,采用表面粗糙散射的指数模型能够使SiC反型层迁移率的模拟结果和实验值符合得更好 .模拟结果还反映出有效横向电场较高时表面粗糙散射的作用会变得更显著 ,电子的屏蔽效应降低了粗糙散射对沟道迁移率的影响 ,温度升高会引起沟道迁移率降低 .     

分形粗糙面双站散射的快速前后向迭代法数值模拟

为模拟复杂分形表面特别是在低掠角入射条件下的双站散射,发展了一种结合前后向迭代方法(FBM)与谱加速算法(SAA)快速求解散射场的Monte Carlo数值方法,计算了在TE,TM锥形波入射在一维分形导体粗糙面的双站散射以及有规则异物存在时的双站散射,讨论了分形粗糙面双站散射的角度性分布与其分数维的关系. 关键词： GFBM/SAA 分形粗糙面 双站散射     

相位微扰法在粗糙面光散射中的应用

根据粗糙面散射理论，用相位微扰法推导出了从随机粗糙介质表面散射的激光雷达散射截面的理论计算公式，计算了几种粗糙表面样品在１．０６μｍ下的单位面积激光雷达散射截面，数值结果与实验数据基本吻合。     

随机粗糙表面上相关点的散射

随机粗糙面上邻近两点的高度与坡度是相关的.由这种相关性对散射的贡献是明显的.在计算粗糙表面散射强度时,应包括这一相关性引起的贡献.本文提供了一种解法和修正后的一维散射强度的解析公式,以及数值计算的实例.     

气体-表面相互作用的分子动力学模拟研究

采用分子动力学模拟方法研究了气体分子Ar在光滑和粗糙Pt表面上的散射规律.提出了一种速度抽样方法,计算了不同温度条件下气体分子对光滑和粗糙表面的切向动量适应系数和吸附概率.结果显示：光滑表面条件下,气体分子的切向动量系数和吸附概率都随着温度的升高而降低;粗糙度对气体分子切向动量与表面的适应具有极大的促进作用,当粗糙度足够大时,切向动量适应系数的大小趋近于1.0,对温度的敏感性也逐渐降低.采用粒子束方法对气体分子在光滑和粗糙表面上的散射规律进行了定量分析.总结了散射过程中气体分子的典型轨迹和动量变化规律,将气体分子在光滑表面的散射分为两种类型：单次碰撞后散射和多次碰撞后散射.单次碰撞后散射的气体分子平均切向动量有所减小,而经过多次碰撞后散射的气体分子则倾向于保持原有的平均切向动量.对于粗糙表面,粗糙度的存在使气体分子与表面间的动量和能量适应更加充分,导致气体分子在较粗糙表面上散射后的平均切向动量大幅减小并接近于0,且气体分子在表面上经历的碰撞次数越多,其散射后的能量损失越严重.     

粗糙面上粒子层矢量辐射传输方程的二阶迭代解法

为了探究典型粗糙面上随机粒子层中能量传输的多次散射机制,提出了一种基于矢量辐射传输方程的建模二阶计算方法.该建模方法将建模场景(粗糙面上粒子层)在高度维(Z轴)划分为多个传输散射层,基于矢量辐射传输理论中的一阶迭代散射解,利用典型粗糙面的半经验半解析方法,求解出整个场景的二阶迭代散射解.同时,研究粒子层能量在粒子与粒子间的多次散射机制,以及粒子与地表粗糙面间的多次散射机制.数值结果表明,该二阶迭代解法相较于矢量辐射传输方程的一阶迭代散射解,能够更完整地探究互作用的散射特性,且可从能量传输角度解译建模场景中物体间的相干作用,从而可用于植被地物环境下的多次散射机制的解析以及散射系数变化趋势的预估.     

Perturbation theory results for the diffuse scattering of light from two-dimensional randomly rough metal surfaces

Using the unitarity and reciprocity preserving formulation of Brown et al a perturbation treatment, correct to fourth order in the surface profile function, is given for the scattering of electromagnetic waves from a weakly rough, two-dimensional, random metal surface. In this formulation the boundary conditions on the electromagnetic fields are satisfied using the extinction theorem in conjunction with the Rayleigh hypothesis and the vector equivalent of the Kirchhoff integral. The theory is applied to, and results are presented for, several different types of rough surfaces which are characterized by power spectra that are extensions to two-dimensional random surfaces of the power spectrum of some one-dimensional random surfaces recently fabricated by West and O'Donnell. These surfaces, which can be realized experimentally, favor coherent, interferent, multiple scattering of electromagnetic waves via surface plasmon polaritons in intermediate states, and clearly exhibit enhanced backscattering caused by the surface plasmon polariton mechanism. Theoretical results are presented for silver surfaces at optical wavelengths.     

Perturbation theory results for the diffuse scattering of light from two-dimensional randomly rough metal surfaces

Abstract

Using the unitarity and reciprocity preserving formulation of Brown et al a perturbation treatment, correct to fourth order in the surface profile function, is given for the scattering of electromagnetic waves from a weakly rough, two-dimensional, random metal surface. In this formulation the boundary conditions on the electromagnetic fields are satisfied using the extinction theorem in conjunction with the Rayleigh hypothesis and the vector equivalent of the Kirchhoff integral. The theory is applied to, and results are presented for, several different types of rough surfaces which are characterized by power spectra that are extensions to two-dimensional random surfaces of the power spectrum of some one-dimensional random surfaces recently fabricated by West and O'Donnell. These surfaces, which can be realized experimentally, favor coherent, interferent, multiple scattering of electromagnetic waves via surface plasmon polaritons in intermediate states, and clearly exhibit enhanced backscattering caused by the surface plasmon polariton mechanism. Theoretical results are presented for silver surfaces at optical wavelengths.     

Angular correlation function of wave scattering by a random rough surface and discrete scatterers and its application in the detection of a buried object

Abstract

The scattering of waves by a buried object is often obscured by the clutter around it. Such clutter can be attributed to the scattering by random rough surfaces and random discrete scatterers. Recent studies show that, because of the memory effect, the angular correlation function can suppress the effects of clutter and make the scattering by the buried object more conspicuous. In this paper, we study the angular correlation function of wave scattering by a buried object underneath a layer of random discrete scatterers and a non-Gaussian random rough surface. Such problems are common when the target is buried below a rough surface that is underneath a layer of vegetation. Numerical results are illustrated for various parameters of rough surfaces and discrete scatterers. The angular correlation function is calculated by frequency and angular averaging. It is shown that the use of the angular correlation function can enhance target detection in the presence of clutter.     

Brewster's scattering angle in scattered waves from slightly rough metal surfaces

Brewster's scattering angle in electromagnetic wave scattering from slightly random metal surfaces is investigated by means of the stochastic functional approach. While there are dips due to Brewster's scattering angle in scattering profiles from dielectric surfaces, Brewster's scattering angle does not exist in scattering from metal surfaces. However, the dips can exist in scattering from rough metal surfaces with the optically denser medium to convert evanescent wave into radiative wave.     

随机粗糙面激光脉冲散射四阶统计特征

依据基尔霍夫近似,推导出一维高斯随机粗糙面四阶统计特性解析式,并获得脉冲波入射下粗糙面双点双频四阶矩互相关函数.数值计算不同入射角,不同高度起伏和相干长度,随机粗糙面双点双频四阶矩互相关函数随相干频谱带宽频差,散射角的变化情况.计算结果表明,高度起伏和相干长度对粗糙面散射四阶统计特的影响很大,粗糙面越光滑,在镜反射方向有最大的四阶矩散射峰值和小的相关带宽.随着粗糙度增加,随机粗糙面脉冲散射的四阶矩的相干分量减弱,展宽现象明显;而相干带宽频差越大,四阶矩衰减越快. 关键词： 四阶矩统计特征 双点双频互相关函数 随机粗糙面 脉冲波散射     

A Study of Optical Backscattering Enhancement from One-Dimensional Rough Surface Using Monte Carlo Method

In this paper, according to Kirchhoff approximation, the optical backscattering enhancement of one-dimensional random rough surface, which includes fractal rough surfaces and random rough surfaces with Gaussian and exponential correlation simulated by Monte Carlo method, is obtained. It is shown that backscattering enhancement of random rough surfaces will increase with increasing the rms height of rough surface for a given correlation length. The angle width of backscattering enhancement is directly proportional to incident wavelength and inverse proportional to correlation length of rough surface. Complex phase of scattering field from superposed rough surface is uniformly distributed, none of the directions is of more overweight. The backscattering enhancement is also studied by wavelet analysis. The numerical results show good consistent with that of the relative references.     

随机粗糙柱面的激光散射特性研究

 扩展面光源如太阳光与激光光源有明显的差异,因此它们照射到随机粗糙柱面后的散射特性也不同。利用随机面元模型,详细分析了刚性随机粗糙柱形表面的激光散射特点,建立了实用化的随机粗糙柱面激光散射理论模型,并给出了正入射时几种情况下的激光散射图像。结果表明,不管哪种情况,正入射时柱面的激光后向散射都很强,而偏离后向的激光散射分布与表面的粗糙度及照射光斑与柱面直径的关系等有关。     

Research on synthetic aperture radar imaging technology of one-dimensional layered rough surfaces

A quick and exact imaging method for one-dimensional layered rough surfaces is proposed in this paper to study the scattering characteristics of a layered medium that exists widely in nature.The boundary integral equations of layered rough surfaces are solved by using the propagation-inside-layer expansion combined with the forward and backward spectral acceleration method(PILE+FB-SA),and the back scattering data are obtained.Then,a conventional synthetic aperture radar(SAR) imaging procedure called back projection method is used to generate a two-dimensional(2D) image of the layered rough surfaces.Combined with the relative dielectric permittivity of realistic soil,the random rough surfaces with Gauss spectrum are used to simulate the layered medium with rough interfaces.Since the back scattering data are computed by using the fast numerical method,this method can be used to study layered rough surfaces with any parameter,which has a great application value in the detection and remote sensing areas.