共查询到14条相似文献,搜索用时 140 毫秒
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采用指数型分布粗糙面模拟实际的粗糙地面,运用FDTD方法研究了超宽带高斯脉冲电磁波入射粗糙地面时的宽带前向电磁散射问题;通过数值计算得到前向散射系数随频率的变化曲线,并与时谐场源激励下的结果进行了对比;分析了不同的粗糙地面高度起伏相关长度、均方根高度,土壤湿度和入射角下前向散射系数随频率的变化关系,得到了指数型分布粗糙地面的宽带前向电磁散射特性。数值计算结果表明各参数的变化对前向电磁散射系数的影响比较明显,入射波不同极化方式下的前向散射系数也有显著变化。 相似文献
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采用改进的分形模型来模拟实际的粗糙海面,应用矩量法研究了一维改进的分形海面及其上方矩形截面导体柱复合电磁散射特征,得到了复合散射系数随散射角的变化曲线,讨论了海面风速、矩形截面柱尺寸、矩形截面柱中心高度以及入射波频率对复合散射系数的影响.结果表明海面风速对复合散射系数的影响明显,而矩形截面柱尺寸、矩形截面柱中心高度、入射波频率对复合散射系数的影响较小. 相似文献
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采用一维带限分形函数模拟实际的粗糙地面,应用时域有限差分法研究了一维分形地面与半埋矩形截面目标复合电磁散射特性,得出了复合散射系数随散射角变化的曲线,分析了分形地面粗糙度参数、土壤介电参数、目标几何参数等对复合散射系数的影响,得到了分形地面与半埋目标复合电磁散射的特性.数值计算结果表明复合散射系数受地面粗糙度参数影响明显,目标表面散射波对表面镜反射方向复合散射系数影响较大. 相似文献
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基于实际海面与下方目标的复合散射在海洋工程、辐射定标及水下目标探测等方面的应用需求,采用改进的一维分形模型模拟实际海面,运用矩量法研究了海面与其下方梯形截面柱体目标的复合电磁散射特性,借助数值计算获得复合散射系数随散射角变化的曲线,详细讨论了海面风速、海面的分维数、海水温度、目标物的尺寸和深度及入射波的频率对复合散射系数的影响.结果表明,海面风速、分维数、入射波的频率对复合散射系数的影响明显,海水温度、目标物的尺寸及深度对复合散射系数的影响较小. 相似文献
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指数型粗糙面与全埋目标的复合电磁散射研究 总被引:2,自引:2,他引:0
采用Monte Carlo方法模拟一维指数型粗糙土壤表面,运用矩量法研究了一维指数型粗糙土壤表面与下方二维导体方形截面柱体的复合电磁散射.通过数值计算得到了复合散射系数随散射角的变化曲线,并将目标尺寸趋于零和目标深度趋于无穷大时的结果与单独粗糙面FDTD结果进行了比对,验证了该算法的正确性.讨论了粗糙面高度起伏均方根、... 相似文献
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指数型粗糙面由Monte Carlo方法来模拟,运用矩量法(MoM)研究了指数型粗糙面下方介质中的电磁波透射特征.其中,入射波为平面波加高斯窗函数后的Thorsos锥形波.通过计算得到了透射系数随透射波散射角变化的曲线,分析了透射系数与粗糙面高度起伏均方根、相关长度、介质介电常数、入射波频率之间的依赖关系.结果表明粗糙面高度起伏均方根、相关长度、介电常数的实部、入射波频率对透射系数的影响明显,而介电常数的虚部对透射系数的影响较小. 相似文献
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He Xiao-xiang Xu Jin-ping 《Frontiers of Electrical and Electronic Engineering in China》2006,1(1):88-91
The Leontovich impedance boundary condition (IBC) is combined with the edge-based finite element method (FEM) in this paper
to analyze the electromagnetic (EM) scattering of cavities coated with a multilayered dielectric. The IBC on the surface of
the medium and the boundary integral equation on the aperture of the cavity are transformed into the third boundary condition,
and then the functional of the boundary value problem is obtained. The surface impedance of the layered dielectric is calculated
by the generalized reflection coefficient; hence, the multireflection of the EM wave in the dielectric is involved. As a result,
the IBC is improved. Numerical results are presented, which demonstrate that the presented IBC/FEM approach is accurate and
convenient for the analysis of EM scattering of open-ended cavities coated with the dielectric.
Translated from Journal of Nanjing University of Aeronautics and
Astronautics, 2004, 36(1): 44–47 (in Chinese) 相似文献
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C. Y. Hsieh 《Electrical Engineering (Archiv fur Elektrotechnik)》2001,83(4):213-222
Contents The like- and cross-polarized scattering coefficients of electromagnetic waves from random rough surfaces corrected by shadowing
functions are studied in this paper. Due to the use of approximate tangential surface fields in the derivative of all the
wave scattering from randomly rough surfaces, the shadowing functions should be added to correct the scattering especially
from surfaces with large rms surface slope. For correct prediction to the scattering characteristics we apply the suitable
angular shadowing function to the single and multiple scattering coefficients respectively. The comparisons of scattering
coefficients with or without shadowing functions are shown in this paper to evaluate the conditions of angular shadowing functions
and the effect of shadowing function for the scattering from random very rough surfaces. We also compare the shadow-corrected
scattering coefficients with the measured data and find the good agreements between them.
Received: 12 December 2000 相似文献
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Calame J.P. Garven M. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(2):287-295
Finite difference quasi-electrostatic simulations are used to predict the interfacial dielectric permittivity of a rough-surfaced contact zone between two distinct materials in a layered composite. Fractional Brownian surfaces, which have fractal geometry, are used to represent the rough interfaces in a model space. The interfacial simulations are combined with a macroscopic analytic model for planar dielectric layers, which allows the calculation of composite permittivity for a layered composite with an arbitrary ratio of surface roughness-to-layer thickness and arbitrary volumetric filling fractions of the constituents. Examples are given for a ceramic-polymer system, and the effects of alternate ratios of constituent dielectric permittivities and changes in surface fractal character are also explored. Compared to the behavior of composites with perfectly flat interfaces, the rough-surfaced composite exhibits a significantly earlier increase in permittivity as a function of the volumetric filling fraction of the higher permittivity material. The behavior with extremely rough surfaces tends towards the predictions of the effective medium approximation 相似文献