Computation of Approximate Polynomial Solutions to TE Modes in an Arbitrarily Shaped Waveguide

Computer programs have been developed to investigate the construction of polynomial approximations to H-modes in empty guide of arbitrary shape. Mathematically this corresponds to the approximate solution of the Helmholtz equation with homogeneous Neumann boundary conditions. The method used is the well-known Rayleigh-Ritz. Both polynomial and piecewise polynomial function spaces have been investigated for several types of waveguide cross section. Particularly good results have been obtained for convexguides.A comprehensive set of H-mode contour plots are presented for four well-known guide sections.     

异向回旋媒质平板波导的模式特性分析

研究了异向回旋媒质平板波导中电磁波的模式特性,给出了电磁波在异向回旋媒质中的导行条件。根据媒质介电常数张量分量取不同的符号,分4类情况分析不同媒质参数条件下传播模式的特性,并讨论了不同情况下虚横波数模式的存在性。结果表明这种媒质中的电磁波模式与一般媒质有很大不同。     

Analysis of a Three-Dimensional Arbitrarily Shaped Dielectric or Biological Body Inside a Rectangular Waveguide

This paper presents a method for the analysis of three-dimensional arbitrarily shaped dielectric obstacles inside a rectangutar waveguide. The numerical computation involves a dyadic Green's function containing a double infinite series, which is evaluated by a partial summation technique.     

对称非线性薄膜波导TE模的色散特性

用均匀（重整化）微扰方法分析Ｋｅｒｒ型非线性薄膜两侧为折射率相等的包层与衬底情形ＴＥ模的传播特性，传播常数用表征非线性的功率密度极值作为参数来表示。在微扰法失效情况下，用数值积分法求解。本文方法简便，节省机时，对典型实例的计算结果与精确数值计算结果十分符合。     

Propagation Losses of Guided Modes in an Optical Graded-Index Slab Waveguide with Metal Cladding

Analytical results for propagation Iosses of guided modes in a graded-index slab waveguide (GISW) with metal cladding are presented. When the permittivity in the guiding layer decreases linearly away from the metal surface, the attenuation constant alpha/sub G/ of well-guided modes, TE and TM, is approximately proportional to only the ratio (Delta epsilon/sub i/ / epsilon/sub 0/) / d/sub i/, where Delta epsilon/sub i/ is the increment in the permittivity at the metal surface in the direction of the polarization of optical waves, d/sub i/i is the diffusion depth in this direction, and epsilon/sub 0/ is the permittivity of free space.     

TE振荡模在含各向异性左手材料劈形平面波导中的传输

研究了含各向异性左手材料的劈形平面波导TE振荡模的传输特性.首先,从麦克斯韦方程组出发,得到该模的色散方程、反射系数方程、传输系数方程以及功率损耗方程.然后,根据这些方程画出了相关特性曲线并对这些曲线进行了仔细分析,研究发现:(1)当模阶数m=0,1,2时,TE模的有效折射率具有较大的值,且随着波导长度的增加而快速减小;(2)TEo模具有超大的反射系数,最大值接近0.967;(3)TEo模传输系数总是小于等于1.2×10-3;(4)当劈形波导斜率k=0.01时,其功率损耗大于等于0.998,而且,当频率为5.0 GHz时,功率损耗仍大于等于0.98.     

Rigorous Analysis of the Scattering of Surface Waves in an Abruptly Ended Slab Dielectric Waveguide

The reflection and the scattering properties of even TE and TM surface waves incident in an abruptly ended dielectric slab waveguide are analyzed. The discontinuity is regarded as a junction between two open waveguides namely the dielectric slab waveguide and the free space waveguide. The boundary conditions acting together with the orthogonality provide singular coupled integral equations on the discrete and the continuous wave amplitudes at the discontinuity. These singular coupled intergral equations with Cauchy kernels and infinite limits of integration are solved by iteration via the Neuman series. Numerical results are presented for the reflectivity of the even TE/sub 0/ and TM/sub 0/ fundamental modes, together with their mode conversion on even TE/sub 2/ and TM/sub 2/ in a slab where two guided modes can propagate. Reflectivity and mode conversion of higher order excitations are also investigated     

Excitation and Scattering of Guided Modes on a Helically Corrugated Dielectric Cylinder

The excitation and scattering of guided modes on a dielectric cylinder with a helical corrugation are investigated. A finite number of radiatiorr modes and an infinite number of surface modes are considered, with the consequence that both the amplitude and phase of the interacting modes can be evaluated. The effect of the pitch angle on the coupling and conversion between the guided modes and the radiation modes of various polarizations is investigated. It is found that TE/sub 0/ guided modes undergo a Brewster phenomenon in the low permittivity dielectrics. The power conservation relation is developed and the reciprocity relations are treated. The aperture fields are used to study the radiation characteristics of a novel dielectric-helix antenna capable of yielding a circularly, elliptically, or linearly polarized radiation.     

AIM Analysis of Electromagnetic Scattering by Arbitrarily Shaped Magnetodielectric Object

A fast solution to the electromagnetic scattering by large-scale three-dimensional magnetodielectric objects with arbitrary permittivity and permeability is presented. The scattering problem is characterized by using coupled field volume integral equation (CF-VIE). By considering the total electric and magnetic fields, i.e., the sum of incident fields and the radiated fields by equivalent electric and magnetic volume currents, the CF-VIE can be established in the volume of the scatterers. The resultant CF-VIE is discretized and solved by using the method of moments (MoM). For large-scale scattering problems, the adaptive integral method (AIM) is then applied in the MoM in order to reduce the memory requirement and accelerate the matrix-vector multiplication in the iterative solver. The conventional AIM has been modified to cope with the two sets of equivalent volume currents.     

Analysis of Arbitrarily Oriented Microstrip Transmission Lines in Arbitrarily Shaped Dielectric Media Over a Finite Ground Plane

A numerical analysis is presented for a multiconductor transmission line in multilayered Iossy, dielectric regions where the ground plane is of finite extent. The transmission fines are infinitely long and vary in cross section from finite to infinitesimally thin. The Green's function for such a two-dimensional transmission line involves an arbitrary constant. If the ground plane is infinite, the method of images could be used where this constant cancels out. However, in the case of a finite ground plane, the constant has to be evaluated. Here a numerical method is presented where the constant could be eliminated rather than evaluated by imposing the condition for the total charge to be zero. The transmission lines, dielectric regions, and the ground plane can have arbitrary cross sections.     

Input Admittance of a Circular Waveguide Aperture Covered by a Dielectric Slab

The input admittance of a circular waveguide opening onto an infinite flange with a homogeneous lossy dielectric coating is derived using integral transforms and assuming the dominant TE11mode as the trial field at the aperture. Admittance calculations for low-loss dielectric sheets of various thicknesses are given and compared with measurements obtained using ground planes of varying sizes. Excellent agreement with theory is obtained for the circular waveguide terminated into a square ground plane only1lambdato2lambda. on a side. A quantitative comparison of the surface wave contribution to the total admittance is also given.     

Propagation in Dielectric Slab Loaded Rectangular Waveguide

Propagation in dielectric loaded rectangular waveguide is investigated theoretically for varying slab thickness and dielectric constant. The slabs are placed across the center of the waveguide in the E plane. This geometry is found to offer bandwidths in excess of double that of rectangular waveguide for dielectrics having dielectric constants of approximately 18. Power handling capacities which are double or triple that of standard waveguide are achievable using the dielectric loaded waveguide. In addition to the theory, design curves of bandwidth, guide wavelength, cutoff wavelength, impedance, power handling capacity, wall losses, and dielectric losses are presented and compared to experiment where possible.     

Electromagnetic Scattering From Arbitrarily Shaped Dielectric Bodies Using Paired Pulse Vector Basis Functions and Method of Moments

A pair of orthogonal pulse vector basis functions is demonstrated for the calculation of electromagnetic scattering from arbitrarily-shaped material bodies. The basis functions are intended for use with triangular surface patch modeling applied to a method of moments (MoM) solution. For modeling the behavior of dielectric materials, several authors have used the same set of basis functions to represent equivalent electric and magnetic surface currents. This practice can result in zero-valued or very small diagonal terms in the moment matrix and an unstable numerical solution. To provide a more stable solution, we have developed orthogonally placed, pulse basis vectors: one for the electric surface current and one for the magnetic surface current. This combination ensures strongly diagonal moment matrices. The basis functions are suitable for electric field integral equation (EFIE), magnetic field integral equation (HFIE), and combined field formulations. In this work, we describe the implementations for EFIE and HFIE formulations and show example results for canonical figures.      

Scattering and Mode Conversion of Guided Modes by a Spherical Object in an Optical Fiber

The scattering and the mode conversion of the guided modes due to a spherical object in a step-index optical fiber is analyzed theoretically. The incident fiber mode is expanded in terms of the spherical vector wave functions, and the scattered fields are obtained by applying the boundary conditions on the surface of the object with the aid of these expansions. The expression for the total scattered power and the mode conversion coefficients are given. As an example, the scattering and mode conversion caused by a spherical air bubble are evaluated numerically.     

含石墨烯多层结构左手材料平面波导TM振荡模的传输特性

对含石墨烯多层结构左手材料的介质特性及其构成的平面波导TM振荡模的传输特性进行了研究。该波导的芯层为含石墨烯的多层结构,覆盖层和衬底为不同的普通材料。计算结果表明:随着归一化波导厚度的增加,TM振荡模的有效折射率同时具有增加和减小,且两者最终达到平衡的双模简并特性。上述特性可以通过调节石墨烯外加电压的方法实现;进一步研究发现,波导中传输的归一化功率流具有正值、负值和零三种情况。电压或者频率的变化对正功率流的影响较小,对负功率流和零功率流的影响较大。     

Finite-Element Analysis of H-Plane Waveguide Junction with Arbitrarily Shaped Ferrite Post

A numerical approach for solving the problem of H-plane waveguide junctions with Iossy ferrite posts of arbitrary shape is proposed. The junctions are allowed to have arbitrary cross section. The approach is a combination of the finite-element method and the analytical method. To show the validity and usefulness of tbe method, Y-junction circulators with a circular ferrite post are considered. Our results agree well with earlier experimental and theoretical results. The performances of Y-junction circulators with a triangular equilateral ferrite post or a triangular ferrite post having depressed sides are investigated. The influences of the ferrite losses on the performance are examined.     

Analysis of Electromagnetic-Wave Modes in Anisotropic Slab Waveguide

Electromagnetic-wave modes propagating in anisotropic slab waveguide are analyzed theoretically in detail. The propagation conditions are derived under which waves can propagate along the axis of the guide. A two-dimensional three-layered waveguiding structure consisting of an anisotropic dielectric slab coated on, or immersed in, isotropic surrounding substrate materials is considered as a typical configuration of the guide. Field-intensity distributions of the propagating modes and their propagation constants are obtained by numerical computations. Techniques for achieving the mode discrimination and the single-mode operation are given. Some possible applications in integrated optics are suggested.     

Analysis of Radiation Phenomena in a Wedge Ended Dielectric Slab Waveguide

Radiation phenomena observed in a wedge shape ended dielectric slab waveguide are analyzed using mode matching technique. The case of transverse electric polarization (TE) being parallel to dielectric slab waveguide is assumed. In order to describe the fields in the wedge region, a stack of dielectric plates is assumed and in each layer the fields are expanded in terms of the mixed spectrum of guided and radiated modes. A similar expansion is used in the constant thickness slab waveguide while in free space medium a continuous-radiation mode expansion is used. Then a mode matching approach is applied, incorporating the orthogonality properties of mixed spectrum modes, in order to compute the wave fields inside the dielectric slab waveguide and wedge medium. Mode matching is achieved by discretizing the continuous radiation mode spectrum leading into a numerically stable solution provided a sufficient large number of points are used to convert integrals into finite summations. Numerical computations are carried out for various wedge geometries and shapes including linear and exponential profiles.     

介质基片上导带TM散射的矩量法计算

用矩量法、预条件共轭梯度法和快速傅立叶变换相结合的混合技术来快速计算介质基片上导体带的TM散射。在这个问题的矩量法计算中,构造阻抗矩阵要耗费大量的CPU时间。这里着重考虑了缩短阻抗矩阵填充时间的方法,提出了按周期分段积分法来处理所涉及的高振荡性Sommerfeld积分．使阻抗矩阵的填充时间大大缩短。