Electromagnetic coupling between two half-space regions separatedby two slot-perforated parallel conducting screens

The problem of electromagnetic coupling between two half-space regions separated by two slot-perforated parallel conducting planes is investigated. A general moment solution for the problem is obtained. This moment solution is then specialized to the case of narrow slots and to a TE (transverse electric to the slot axis) excitation. Attention is given to the power transmitted from one half-space to the other through the slots and to its functional dependence on various problem parameters involved     

Comment on “Electromagnetic coupling between two half-spaceregions separated by multiple slot-perforate parallel conductingscreens”

El-Hajj, Kabalan and Khoury (see ibid., vol.37, p.105, 1995) have analyzed electromagnetic coupling between two half-space regions through multiple slotted parallel conducting screens by the method that they have used to analyze another problem. The main contribution of the above paper is a numerical method instead of a matrix inverse method to directly solve the unknown magnetic current. However, the authors used the wrong Green's function to compute the admittance matrix element     

Electromagnetic transmission through narrow slots in thick conducting screens

The general formulas for electromagnetic transmission through an infinitely long slot in a perfectly conducting screen of finite thickness are specialized to the case of a narrow slot. The slot may be filled with a homogeneous isotropic material. A simple equivalent circuit for the narrow slot is developed. It is found that for certain screen thicknesses the slot becomes resonant, and exceptionally large transmission of energy may occur. In fact, as the slot width approaches zero, the transmission width at resonance becomes1/piwavelengths regardless of the actual slot width. The effect of loading the slot with a lossy dielectric is also considered. Computations are given to illustrate the validity of the equivalent circuit model and the accuracy of transmission characteristics computed from it.     

TM scattering from slits in thick parallel conducting screens

TM-wave scattering from slits in thick parallel conducting screens is analyzed using the Fourier transform. The simultaneous equations for the modal coefficients are formed in terms of convergent series. Numerical computations are performed to illustrate the behavior of transmission and scattering from the slits. High-frequency solutions for scattering and transmission are obtained in approximate closed forms     

Electromagnetic plane wave scattering by a system of two parallel conducting prolate spheroids

By means of modal series expansions of electromagnetic fields in terms of prolate spheroidal vector wave functions, as exact solution is obtained for the scattering by two perfectly conducting prolate spheroids in parallel configuration, the excitation being a monochromatic plane electromagnetic wave of arbitrary polarization and angle of incidence. Using the spheroidal translational addition theorems recently presented by the authors which are necessary for the two-body (or multibody) scattering solution, an efficient computational algorithm of the translational coefficients is given in terms of spherical translational coefficients. The field solution gives the column vector of the series coefficients of the scattered field in terms of the column vector of the series coefficients of the incident field by means of a matrix transformation in which the system matrix depends only on the scatterer ensemble. This eliminates the need for repeatedly solving a new set of simultaneous equations in order to obtain the scattered field for a new direction of incidence. Numerical results in the form of curves for the bistatic and monostatic radar cross sections are given for a variety of prolate spheroid pairs having resonant or near resonant lengths.     

Analysis of coupling between two parallel dielectric waveguides

The coupling between two parallel dielectric waveguides with a finite coupling length is investigated. The ends of the waveguides are tapered in order to reduce the scattering losses. It is shown that the taper sections can be utilized to achieve an effective coupling which is insensitive to the coupling length, thus, providing a much greater tolerance for the design and manufacturing of coupling devices.     

Electromagnetic interaction between two parallel circular cylinderson a planar interface

Multiple interaction between two parallel and infinitely long circular cylinders on a planar interface separating two different media is analyzed theoretically. The scattering equations are derived from the so-called extinction theorem applied to this particular geometry. For simplicity, the surface is considered to be perfectly conducting although the method can be extended for any material. The equations, solved numerically by means of an appropriate discretization of the surface, provide the electric surface current density from which the scattered intensity can easily be calculated. Scattering of the transversal-magnetic and transversal-electric incident wave is studied as a function of the cylinder separation for cylinder diameters from 0.2λ to 4λ (λ being the incident wavelength). The effects of the interaction between cylinders are shown in the scattering cross section and in the surface current density of the planar substrate and of the cylinders     

半空间环境中任意位置三维导体目标的电磁建模

采用基于混合位积分方程的数值方法对半空间环境中任意位置(包括界面上方、下方以及跨界面情形)的三维导体目标进行电磁建模,并通过以下两个途径来提高求解效率:一是优化阻抗矩阵的生成过程来避免格林函数的重复计算;二是在不同场源距离区域使用不同的索末菲积分计算方法(包括折合积分路径方法、最陡下降路径方法以及离散复镜像方法)来提高格林函数的单次计算效率.数值结果表明,该方法能方便地对半空间环境中任意位置目标电磁辐射与散射进行精确数值计算,同时具有较高的计算效率.     

Electromagnetic coupling through small apertures in a conducting screen

The electromagnetic field coupling through small apertures illuminated by an arbitrary incident plane wave is discussed for general aperture shapes. A set of new integral equations in a form highly amenable to numerical solution techniques is derived. Based on the application of the Rayleigh series method, an analytical solution is obtained for the first few terms of the expansion of the apertureE- field of a circular aperture. Numerical results are also constructed for the aperture field and the diffracted field of small rectangular apertures and compared with those of the circular apertures.     

Mutual coupling between two waveguide radiators on a conducting concave sectoral surface

An approximate theoretical expression for the mutual coupling between two waveguide radiators directed radially inward and located on a perfectly conducting concave sectoral surface has been developed using reaction concept. The radius of curvature of the surface is assumed to be large so that the apertures can be considered on locally plane surface. The theoretical and experimental results show close agreement.     

电磁波对不规则地面上架空线的影响

对不规则金属地表面上有限长架空线受平面电磁波影响的问题提出了一个有效的解决方案 :采用复合矩量法求解不规则地表面对平面电磁波的散射 ,再针对具有分布源的架空通信传输线 ,采用解析与数值相结合的方法求解。详细地介绍了求解平面电磁波对不规则地面上架空线影响的理论分析和计算过程 ,并且针对实际工程应用的典型参数给出了计算实例并讨论了计算结果。该方案也适用于航行轮船及待发射飞行器表面上通信电缆的电磁干扰问题     

基于并行技术的机载多天线耦合快速算法

分析机载天线间的干扰情况必须首先解决电大尺寸电磁计算问题.首先讨论一种基于空域分解技术及局域网技术的并行数值算法,这种算法将一个电大尺寸散射体表面划分为一系列子域分别进行处理,在求解子域电流的过程中使用了快速多极子技术进行加速运算,然后运用这种算法对机载天线间的耦合进行分析并对算法的性能进行了总结.     

Electromagnetic scattering by two parallel dielectric ellipticcylinders

The transverse magnetic (TM) multiple scattering by two parallel homogeneous dielectric elliptic cylinders is investigated. The solution is an exact one and based on the separation of variables technique in conjunction with the addition theorem for Mathieu functions. It is expressed in terms of a system of simultaneous linear equations of infinite order which is then truncated for numerical computations. Representative numerical results with emphasis on the multiple scattering effects on the backscattering echo width are then generated, for some selected parameters, and presented. It is found that the multiple interactions between the two cylinders affect the echo width significantly     

Electromagnetic scattering from multiple rectangular apertures in athick conducting screen

Electromagnetic wave scattering from multiple rectangular apertures in a thick conducting screen is studied. The Fourier-transform and mode-matching technique are used to obtain simultaneous equations for the modal coefficients. The simultaneous equations are solved to represent the scattered and transmitted fields in series forms which are suitable for numerical computation. The numerical computations are performed to illustrate the aperture transmission and scattering behavior in terms of aperture size, incident angle, and frequency. The effects of the finite number of apertures on the transmission characteristics are discussed     

Electromagnetic transmission through multiple circular apertures in a thick conducting plane

The boundary-value problem of electromagnetic wave scattering from multiple circular apertures in a thick conducting plane is rigorously solved. The eigenfunction expansion, integral transform, and superposition principle are utilized to represent the scattered field in the discrete and continuous modes. The boundary conditions are enforced to obtain a set of simultaneous equations for the discrete modal coefficients. The transmission coefficient is represented in a fast convergent series. Computation is performed to illustrate the behavior of transmission and coupling through multiple circular apertures in terms of the aperture geometry.     

Electromagnetic coupling to an infinite wire through a slot in a conducting plane

The problem of electromagnetic coupling to a long wire behind a slot-perforated conducting plane is considered by the method of moments. An equivalent circuit is obtained for the transmission line mode of the wire-slot system. An interesting result of the analysis is that, when the wire is terminated in loads for maximum power transfer, orders of magnitude more power may be transferred through the slot when the wire is present than when the wire is absent.     

Electromagnetic coupling to a conducting wire behind an aperture of arbitrary size and shape

The electromagnetic coupling to a conducting wire behind an aperture in a plane conducting screen is analyzed. The aperture can be of arbitrary size and shape. The wire can be of finite length, with or without terminating loads, or of infinite length. The electric current on the wire and the equivalent magnetic current over the aperture region are calculated by the method of moments. An equivalent circuit for the effect of the aperture on the transmission line mode of the wire is derived.