Transmission through dielectric-filled slots in a conductingcylindrical shell of arbitrary cross section: TE case

A simple moment solution is summarized for the problem of electromagnetic transmission through dielectric-filled slots in a conducting cylindrical shell of arbitrary cross section. The system is excited by a plane-wave polarized transverse electric (TE) to the axis of the shell. The equivalence principle is used to replace the shell and the dielectric by equivalent electric and magnetic surface currents radiating into an unbounded medium. Two different sets of coupled integral equations involving the surface currents are obtained by enforcing the boundary conditions on the tangential components of the total electric and magnetic fields. The method of moments is used to solve the integral equations. Pulses are used for both expansion and testing functions. Special attention is paid to circular and rectangular shells. Results for shell surface current, the internal field, and the aperture field are presented. For the case of air dielectric filling, the results computed using the electric field and/or the magnetic field formulation are in very good agreement with published data. In general, it is observed that the effect of filling a slot with a dielectric is not predictable from a simple theory     

Scattering by a chiral cylinder of arbitrary cross section

An integral equation and method-of-moments (MM) solution to the problem of scattering by an inhomogeneous chiral cylinder of arbitrary cross section is presented. The volume equivalence theorem for chiral media is developed and used to formulate a set of coupled integral equations for the electric and magnetic volume polarization currents representing the chiral cylinder. These coupled integral equations are solved using a standard pulse basis and point-matching MM solution. Numerical results, including echo width and internal fields, are presented for the scattering by chiral slabs and circular cylinders. These results are compared to exact solutions when available     

Scattering by a dielectric cylinder of arbitrary cross section shape

The theory and equations are developed for the scattering pattern of a dielectric cylinder of arbitrary cross section shape. The harmonic incident wave is assumed to have its electric vector parallel with the axis of the cylinder, and the field intensities are assumed to be independent of distance along the axis. Solutions are readily obtained for inhomogeneous cylinders when the permittivity is independent of distance along the cylinder axis. Although other investigators have approximated the field within the dielectric body by the incident field, we treat the total field as an unknown function which is determined by solving a system of linear equations. In the case of the dielectric cylindrical shell of circular cross section, this technique yields results which agree accurately with the exact classical solution. Scattering patterns are also presented in graphical form for a dielectric shell of semicircular cross section, a thin homogeneous plane dielectric sheet of finite width, and an inhomogeneous plane sheet. The effects of surface-wave excitation and mutual interaction among the various portions of the dielectric shell are included automatically in this solutiom     

单轴双各向异性媒质柱体的电磁散射

采用广义多极子技术（Ｇｅｎｅｒａｌｉｚｅｄ Ｍｕｌｔｉｐｏｌｅ Ｔｅｃｈｎｉｑｕｅ,ＧＭＴ）分析了单轴双各向异性媒质任意截面柱体的电磁散射,计算结果与解析解和矩量法（Ｍｅｔｈｏｄ ｏｆ Ｍｏｍｅｎｔｓ,ＭｏＭ）所得结果一致,讨论了该方法在电磁散射应用中的优缺点。     

Backscatter of a large rotating conducting cylinder of arbitrary cross section

A quasi-stationary method in conjunction with geometrical theory of diffraction (GTD) techniques is used for calculating the backscattered field from a large rotating conducting cylinder with an arbitrary cross section. Using this method, the scattered field at each timetis obtained as if the cylinder were stationary. The power density spectrum is then obtained using a Fourier transform. The backscattcr power density spectrum of a large rotating cylinder consists of discrete spectral lines. For an orthogonal polygon-cylinder rotating about its geometrical center axis, the backscatter power density spectrum is symmetric about the incident frequency.     

快速多极子在任意截面均匀介质柱散射中的应用

采用快速多极子法（FMM）加速后的矩量法（MoM）求解由电磁场等效原理导出的关于均匀介质柱表面等铲电磁流的积分方程,进而计算其电磁散射特性,FMM的引入使计算时间和内存开销都从O(N^2）降到O（N^3/2）,且并不增加多少复杂度。最后给出了一些介质柱体RCS的算例。     

Multiple scattering from two dielectric-filled semi-circular channels in a conducting plane: TM case

The behavior of TM-wave scattering from two dielectric-filled semi-circular channels in a perfectly conducting substrate is investigated. The scattered field is represented in terms of an infinite series of radial modes with unknown coefficients. By applying separation of variables and employing the partial orthogonality of sine functions, the unknown coefficients are obtained. The resulting infinite series is then truncated to a finite number of terms to produce numerical results. Plotted results for the radar cross sections reveal how the scattering properties may be varied by changing several physical and geometrical parameters of the structure.     

Electromagnetic scattering from a chiral cylinder of arbitrarycross section

A simple moment solution is presented to the problem of electromagnetic scattering from a homogeneous chiral cylinder of arbitrary cross-section. The cylinder is assumed to be illuminated by either a TE or a TM wave. The surface equivalence principle is used to replace the cylinder by equivalent and magnetic-surface currents. These currents radiating in unbounded external medium produce the correct scattered field outside. When radiating in an unbounded chiral medium, they produce the correct total internal field. By enforcing the continuity of the tangential components of the total electric field on the surface of the cylinder, a set of coupled integral equations is obtained for the equivalent surface currents. Unlike a regular dielectric, the chiral scatterer produces both copolarized and cross-polarized scattered fields. Hence, both the electric and magnetic current each have a longitudinal and a circumferential component. These four components of the currents are obtained by using the method of moments (MoM) to solve the coupled set of integral equations. Pulses are used as expansion functions and point matching is used. The Green's dyads are used to develop explicit expressions for the electric field produced by two-dimensional surface currents radiating in an unbounded chiral medium. Some of the advantages and limitations of the method are discussed. The computed results include the internal field and the bistatic and monostatic echo widths. The results for a circular cylinder are in very good agreement with the exact eigenfunction solution     

Combined field solution for TM scattering from multiple conducting and dielectric cylinders of arbitrary cross section

A simple moment solution is given for the problem of electromagnetic scattering from multiple conducting and dielectric cylinders of arbitrary cross section. The system of conducting and dielectric cylinders is excited by a plane-wave polarized transverse magnetic to the axis of the cylinders. The equivalence principle is used to obtain three coupled integral equations for the induced electric current on the conducting cylinders and the equivalent electric and magnetic currents on the surface of dielectric cylinders. The combined field integral equation (CFIE) formulation is used. Sample numerical results are presented. The agreement with available published data is excellent.     

The application of Lanczos S-expansion method to the solution of TMscattering from a dielectric cylinder of arbitrary cross section

An iterative method of solution of an integral equation arising in electromagnetic scattering from penetrable bodies is presented. The solution method, first discussed by C. Lanczos (1950), is valid for all values of the dielectric constant, and is similar to the Liouville-Neumann series. The series resulting from this method does not have the convergence difficulties associated with the Liouville-Neumann series. Results for several cases are presented to illustrate the utility of the method     

任意截面非均匀各向异性阻抗柱体的电磁散射

采用矩量法(MoM)结合阻抗边界条件研究了二维无限长任意形状截面非均匀各向异性阻抗柱体的电磁散射特性。散射场通过Stratton-Chu电场积分方程、电流连续性方程和二维格林函数予以求解。当柱体截面矢径的模等于恒定值时,目标退化为二维无限长圆柱,提出的计算方法仍然有效。计算得到的散射宽度结果与解析法、物理光学法(PO)的结果进行了比较,吻合良好。     

Radiation from apertures in conducting cylinders of arbitrary cross section

An analysis of two-dimensional radiation from apertures in perfectly conducting cylinders of arbitrary cross section is given. Solutions are expressed in terms of generalized network parameters, obtained by applying moment methods to the superposition integral equation. Formulas are given for current distributions, self- and mutual admittances, and radiation patterns. Representative computations are included to illustrate the theory.     

Scattering cross section of a small radome of arbitrary shape

A simple moment procedure is used to compute the scattering cross section of a small radome of arbitrary shape. Numerical results are presented for a radome with Von Karmon shape and a spherical shell. The computed and exact results for the spherical shell are in good agreement. Data for the Von Karmon shape are presented but not yet assessed. The method presented is found to be mainly limited to radomes in the resonance region since as the size of radome increases, the number of unknowns required for reasonable convergence drastically increases     

Electromagnetic scattering from a spherical nonuniform medium-part II: The radar cross section of a flare

The radar cross section for scattering of electromagnetic waves by a plasma having an electron concentration proportional tor^{-2}is calculated. The exact solution is compared with the scalar approximation. It is found that the exact solution can be orders of magnitude smaller than any of the usual approximations.     

Formation of a bipolar conical beam with an arbitrary cross section

Problems of calculating forming electrodes for fragments of a bipolar diode that have the form of a circular cone or a cone with an arbitrary cross section are considered. Local characteristics of cathode and anode equipotential surfaces are obtained, and their dependence on the configuration of the contour bounding the beam’s cross section is revealed. Theoretical aspects of the technology of manufacturing 3D optoelectronic systems (templates for electrodes) are investigated. The effect of a beam on plane targets of given shapes is studied. Forming electrodes for a relativistic injector with a conical electron beam having an arbitrary cross section are constructed.     

Electrooptic modulation in an arbitrary cross section waveguide

The electromagnetic field of an optical wave of frequency ω, traveling through a long, electrooptic waveguide of arbitrary cross section and composition in the presence of an arbitrary external field of strength E^ext and radio frequency Ω, is derived by a perturbative argument, assuming Ω/ω≪1 and | r_ijkE^ext|≪1, where r _ijk are the linear electrooptic coefficients. An idealized model is solved exactly in the context of rigorous perturbation theory, and the solution is shown to be valid whenever (r_ijk E^ext)²ω/Ω≪1, without restriction on r_ijkE^extω/Ω. The arbitrary cross section formula, when evaluated in the model case, agrees exactly with the rigorous result, so it is argued that the arbitrary cross section formula should also be valid whenever (r_ijkE^ext)² ω/Ω≪1     

任意截面波导的模式截面场的数值分析

给出了任意截面波导的传输特性的时域差分（FDTD）数值方法的一般分析方法,首次提出了用数值方法建立任意截面波导中各模式横向场分量截面场分布的方法,为证明这种方法的有效性,计算了常用空气填充的Ka波段矩形波导中主模（H10模）和一次高阶模式H20模的截止波长和Ey场分量,其与理论值的安全一致性表明所提出的方法是正确的。作为应用例子给出了一种新型的五边形波导的最低四个模式的传播常数及主模式和第一高次模的电场在波导横截面的场分布图。     

The scattering cross section of a composite cylinder, geometric optics

The optical analogue of the scattering cross section of a composite cylinder is developed from a representation of the forward scattered amplitude as a continuous spectrum of radial eigenfunctions. The Debye approximation for the Hankel functions, which is valid when their arguments are large compared to the order, leads to a series of integrals which can be evaluated asymptotically by the method of stationary phase. The final result, for a certain range of parameters, is a diffraction correction plus a double sum of terms, each of which can be interpreted as an optical ray. It is shown that if the angular displacement between the incoming and scattered ray directions is(2m + 1)pi, the ray must have been reflected at the conducting core of the cylinder at least2m + 1times. After the parameter ranges to which these results apply were determined, the nonlinear equations for the ray angles were solved on a large-scale digital computer and the scattering cross section of a number of composite cylinders was calculated as a function of frequency. The results are presented graphically.     

Analysis of dielectric waveguide structure of arbitrary cross section

A class of dielectric waveguide structures of arbitrary cross section in conjuction with one or more layer dielectrics is ana lysis with the Method of Lines(MOL). This leads to an eigenvalue problem where the nonphysical and spurious modes do not appear. Dispersion characteristic examples are calculated for structures suitable for mm waves and optical integrated circuits. Such as ridge guides, guide, and so on. The numerical examples are verified by results available from other methods.     

Analytic method of arbitrary cross section open groove guide

Groove guide is one of the waveguides that have been used at millimeter and submillimeter waveband. This paper analyzes arbitrary groove guides by means of the eigen-weighted boundary integral equation method that uses the eigenfunctions of a fictitious regular boundary as weighting functions. In comparison with the theoretical and experimental results published, the numerical results for rectangular, circular and V-groove guides using this method are exact enough with fast convergence and less calculation.