共查询到18条相似文献,搜索用时 156 毫秒
1.
精确阻抗边界条件的推导 总被引:3,自引:0,他引:3
针对Leontovich阻抗边界条件IBC是近似阻抗边界条件这一不足之处,本文利用电磁场理论中的一般边界条件和麦克斯韦方程,考虑到平面波的传播特点,导出了不含近似的精确阻抗边界条件(EIBC),给出了精确阻抗这界条件一般矢量表达式及其在直角坐标系和柱坐标系中的表达形式。导出的结果显示,Lontovich阻抗边界条件只是精确阻抗边界条件一个特例。 相似文献
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比较详细地阐述了用于电磁散射计算的阻抗边界条件,指出标准阻抗边界条件、广州义阻抗边界条件及精确阻抗边界条件的应用范围,讨论了表面阻抗的各种表示式,上述问题对散射场的计算是非常有用的。 相似文献
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本文把应用于理想导体劈中的等效边缘电磁流概念推广应用到阻抗劈上,导出了劈边缘在产面波斜入射情况下与阻抗劈绕射密切相关的等效边缘电磁流表达式,然后利用辐射积分公式,给出了有限长直劈的电磁散射解。为计算平板模型机翼的RCS打下了理论基础,文中给出的计算实例说明了本文方法的有效性。 相似文献
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从Maxwell方程出发,研究了平面波入射到空气和左手媒质的分界面上时,界面附近的电磁场,并将电场和磁场的关系表示为阻抗边界条件表达式,然后与右手媒质的阻抗边界条件进行对比,指出其形式上的统一和计算公式的区别。在此基础上,对多层媒质引用传输线法进行分析,并采用其给出的多层媒质的反射系数计算公式,计算了多层媒质内包含左手媒质时的表面反射系数,并对多层媒质包含左手媒质和右手媒质的情形进行了对比,研究了其反射系数幅度和相位的异同。最后将边界条件应用到阻抗半平面的散射场的计算中,探讨了平面波入射到单面涂敷左手媒质的阻抗半平面上时的散射场,并对场的计算公式作了简单分析。 相似文献
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本文应用广义阻抗边界条件研究了二维平板结构上介质填充凹槽的散射特性。通过选择合适的系数,广义阻抗边界条件可以模拟槽内任何特征的材料.将凹槽内的介质填充层由其表面上的简单边界条件来替代,所得的积分公式可用CGFFT法求解,且对任意入射角的表面散射场能作出精确的预估。 相似文献
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在求解各向异性介质涂敷物体的电磁散射中,采用高阶各向异性阻抗边界条件可以简化求解过程,提高近似解的精度。文中采用谱域法法导出各向异性介质涂敷平面的二阶张量阻抗边界条件,并通过例子证明其精确性。 相似文献
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涂覆各向异性复合手征介质的阻抗圆柱体的雷达截面积 总被引:3,自引:0,他引:3
本文解决了平面波入射时涂覆各向异性复合手征介质的阻抗圆柱体的电磁散射问题。首先推导得到各向异性复合手征介质层中电磁场量的基本方程;然后根据边界条件得出计算所讨论的阻抗圆柱体的雷达散射截面的解析表达式。文中还给出若干数值结果。 相似文献
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本文解决了平面波入射时涂覆各向异性复合手征介质的阻抗圆柱体的电磁散射问题。首先推导得到各向异性复合手征介质层中电磁场量的基本方程;然后根据边界条件得出计算所讨论的阻抗圆柱体的雷达散射截面的解析表达式。文中还给出若干数值结果。 相似文献
11.
Ali Yapar Hülya ahintürk brahim Akduman 《AEUE-International Journal of Electronics and Communications》2002,56(3)
In this paper, the electromagnetic scattering problem related to a circular cylinder with inhomogeneous impedance boundary is solved. This kind of problem may have practical applications such as antenna design since one can obtain a certain radiation pattern by choosing thesurface impedance in an appropriate way. The approach presented in this paper is based on the series representations of the scattering and incident fields. The impedance function is also expanded into a Fourier series. By using orthogonality properties of some special functions the problem is reduced to the solution of a system of linear equations. The problem isalso solved through the extended boundary condition method (T-matrix method). Since an extensive treatment of the T-matrix method is available in the open literature the paper is weighted towards the Fourier series method. The results of both methods are compared. Some illustrative examples showing the effects of different parameters on the scattered field are given. 相似文献
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A generalized impedance boundary condition (GIBC) is developed to approximate the scattering of a plane acoustic wave from a bone structure such as a rib. In particular, the rib and surrounding tissue are modeled as a viscoelastic cylinder of infinite length immersed in an infinite, inviscid fluid medium. In order to determine the scattered pressure wave, appropriate boundary conditions are imposed on the relevant differential equations at the fluid-solid surface. The exact solution is then used to develop first- and second-order impedance boundary conditions applicable at the surface of the cylinder. Numerical results demonstrate the improved accuracy of the second order condition 相似文献
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《Antennas and Propagation, IEEE Transactions on》2009,57(8):2397-2408
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Bernard J.M.L. Lyalinov M.A. Ning Yan Zhu 《Antennas and Propagation, IEEE Transactions on》2008,56(6):1616-1623
An analytical-numerical computation of diffraction coefficients is described for a semi-infinite impedance cone of circular cross section illuminated by an electromagnetic plane wave. To enable an incomplete separation of variables, both the incident and scattered fields are expressed in terms of the Kontorovich-Lebedev (KL) integrals; an inversion of the Leontovich condition on the cone's surface yields equations for the spectra, whose Fourier coefficients satisfy certain functional difference equations of the second order; the latter are then converted to integral equations of the second kind which are solved numerically; using the so obtained spectra in the KL-integrals for the scattered field and evaluating the integrals in far field leads to diffraction coefficients. Numerical results are included both for verification purposes and for displaying the diffraction behavior for different incident and diffraction angles, as well as for several cone impedances. 相似文献
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The three dimensional problem of diffraction of a skew incident plane wave by a wedge with anisotropic impedance boundary conditions is explicitly solved by the probabilistic random walk method. The problem is formulated in terms of two certain components of the electric and magnetic fields which satisfy independent Helmholtz equations but are coupled through the first-order boundary conditions. The solution is represented as a superposition of the geometric waves that are completely determined by elementary methods and of the waves diffracted by the apex of the wedge. The diffracted field is explicitly represented as the mathematical expectation computed over the trajectories of a two-state random motion which runs in a complex space and switches states under the control of stochastic equations determined by the problem's geometry and by the boundary conditions. 相似文献
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《Microwave Theory and Techniques》1977,25(11):923-931
In this paper explicit expressions are presented for the guided surface waves and lateral waves that are excited when radiation fields are incident upon rough surfaces. Similarly, expressions are presented for the radiation fields scattered by rough surfaces that are excited by surface waves and lateral waves. In addition, coupling between the surface waves and the lateral waves due to surface irregularities is considered in detail. The solutions, which are based on a full-wave approach to the problem, are subject to the exact boundary conditions at the irregular interface. These are shown to be consistent with the reciprocity relationship in electromagnetic theory. The validity of the approximate impedance boundary condition is examined and consideration is given to excitation at the grazing incidence, the Brewster angle, and to waves incident at the critical angle for total internal reflection. Optimum conditions are determined for coupling between the radiation fields, the surface waves, and the Iateral waves incident upon irregular boundaries. Thus this work is applicable to problems of radio wave propagation near an irregular interface between two media and excitation of guided waves by irregular dielectric structures. 相似文献
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《Microwave Theory and Techniques》1971,19(1):2-8
The propagation of guided waves in a rectangular geometry having impedance boundary conditions is investigated. An impedance compatibility relation is derived that must be satisfied in order that a separable modal solution exists for a given impedance configuration. Several new rectangular waveguides are developed; among them are 1) a tall rectangular waveguide operating in a dominant H/sub 10/ mode with no H/sub 0N/ modes; 2) a rectangular waveguide with two parallel anisotropic impedance surfaces; 3) a rectangular waveguide with two parallel walls having isotropic impedance surfaces, the other two walls being anisotropic; 4) a rectangular waveguide supporting only E modes; and 5) rectangular coaxial systems containing impedance surfaces. The modal structure of rectangular waveguides with impedance boundary conditions offers advantages over the conventional waveguide. The potential of oversizing for low-loss and high-power applications is enhanced because of the additional modal control provided by the impedance surfaces. Other applications are suggested. 相似文献