Electromagnetic wave propagation in multilayer dielectric periodicstructures

The propagation characteristics in multilayer dielectric periodic structures, that extends a previous analysis by introducing additional dielectric layers, is presented. It is applied to propagating electromagnetic modes along the longitudinal and transverse directions of the structure's periodicity. The use of Floquet's theorem reduces the analysis to a single cell of the propagating fields for both, TE and TM polarizations. Results showing the effect of varying the layers thickness and electric permittivity on the propagation constant and on the field distributions within each cell are presented as well as the band structure associated with the periodic structure     

Electromagnetic propagation along contacting dielectric tubes

Experiments performed in the 50?80 GHz band show that single-mode propagation is possible near the contact line of two thin-wall dielectric tubes. The group delay c/vg, is found to be almost a constant(3·3)from 55 to 75 GHz. Pulsespreading is therefore very low for that structure (< 1·6 ns/km?). These experimental results are in good agreement with a semiclassical theory of propagation.     

Electromagnetic wave propagation in almost periodic media

The problem of electromagnetic wave propagation in almost periodic media is investigated, and a solution is obtained directly from Maxwell's equations. The evaluation of this solution involves a generalization to almost periodic media of the Brillouin diagram of periodic media. The Brillouin diagram is used to place in evidence similarities and differences of wave propagation in periodic and almost periodic media. It is shown that although the periodic and almost periodic theories agree in many cases of interest, there exist cases in which distinct differences appear. In particular, these distinctions become apparent for media with closely spaced tones.     

交替隐式时域有限差分分析有耗介质电磁波传播

针对电磁波在有耗介质中的传播特点,提出了改进的交替方向隐式时域有限差分(ADI-FDTD)算法来研究电磁波在有耗介质中的传播特性。改进后的算法可改善传统ADI-FDTD为提高计算效率导致的计算精度下降的缺点。证明了算法的无条件稳定性,并分析了算法的数值色散。通过算例对比验证了算法的有效性和对计算精度的改善。将算法应用到金属球体在空气中、地面上方和海平面上方的电磁散射分析中,仿真结果表明:介质损耗在一定程度增大电磁散射的同时,会加大电磁散射的震荡。     

Electromagnetic wave propagation along a conducting wire in a general magnetoplasma

The propagation constant of the electromagnetic wave along a very thin conducting wire immersed in a magnetoplasma is obtained explicitly for a general case where the dc magnetic field is applied with an arbitrary inclination with respect to the wire.     

Electromagnetic wave propagation in an asymmetrical coal seam

Electromagnetic wave propagation in a coal seam is analyzed for the case where the surrounding floor and roof rocks have different electrical properties. Numerical results are presented for the attenuation rate and field distribution of the dominant mode. Even when the roof and floor conductivities are different, the vertical electric field and the horizontal magnetic field are the dominant components, and they are nearly constant within the coal seam. The results have application to mine communication and remote sensing of coal seams.     

Electromagnetic wave propagation in cylindrically stratified isotropic media

The general electromagnetic field, when independent of axial distance, may be expressed as the sum of E parallel and H parallel partial fields. Exact solutions of the wave equation for the radial variation of the H parallel field are not numerous. Generalised refractive-index profiles are presented which permit transcendental solutions to be made.     

Electromagnetic wave propagation in spherically stratified isotropic media

The general electromagnetic field can be resolved into two components represented by electric and magnetic Hertz vectors, both vectors being parallel to the radial direction. Very few exact solutions for the radial variation of fields of the electric type have been found hitherto. Generalised refractive-index profiles permitting exact transcendental solutions are presented.     

Creeping wave propagation constants and modal impedance for a dielectric coated cylinder

The electromagnetic characteristics associated with the creeping waves supported by a dielectric coated cylinder are investigated. The propagation constants and wave impedances of the creeping waves are obtained numerically. Higher order modes which are significant for a thick coating are also investigated. The propagation constants and creeping wave modal impedance are compared with those obtained for a planar dielectric slab backed by a ground plane. It is found that, contrary to the planar configuration, no cutoff frequencies exist for the creeping waves associated with the coated cylinder. In fact, the coated cylinder supports an infinite number of modes. However, depending upon the thickness of the coating, only a few Elliott type creeping wave modes with low attenuation can exist. Furthermore, for each of the Elliott type creeping waves, there is a critical radius for the cylinder below which the Elliott type creeping wave cannot exist. The results are also compared with an impedance boundary cylinder, where the impedance is chosen to be purely imaginary.     

Electromagnetic wave propagation in magnetic multilayers— Non-reciprocal reflections

A theory of EM wave propagation through magnetic multilayers and superlattices is presented based on the propagation matrix of a magnetic film. By using theP matrix, the transmission and reflection coefficients of layered magnetic media, including: (1)semi-infinite magnetic surfaces, (2) magnetic multilayers, (3) semi-infinite magnetic superlattices are obtained. The numerical results show that the EM modes of a magnetic layer system is excited and manifested as the sharp dips in theS-polarized reflection and the dispersion curves of the magnetic polaritons can be measured by a method similar to the attenuated total reflection (ATR) technique. Supported by the National Natural Science Foundation of China     

Generation of millimeter wave Gaussian beams and their propagation in a dielectric waveguide

Linearly polarized fundamental mode Gaussian beams were generated and coupled to a hollow circular oversized dielectric waveguide by placing the waist of the beam at the guide entrance. The transmission properties of the waveguide were characterized as a function of frequency for a variety of coupling conditions. These conditions included changes in the input beam waist radius, angle of incidence, and displacement perpendicular and parallel to the guide axis. It has been found that: 1.) power transmission is maximized when the waist of the input beam is centered at the guide input, injected normally, and has a radius of 0.43 times the waveguide radius, 2.) power transmission decreases rapidly with increasing angle of incidence and the rate of that loss increases with frequency, 3.) the waveguide preserves the linear polarization of the input beam, 4.) power transmission in the fundamental waveguide mode is not greatly affected by moderate displacements in the input beam position, and 5.) upon exit from the waveguide the launched EH₁₁ mode propagates as a fundamental mode Gaussian beam in the quasi-far field. The results compare favorably to the transmission theory of Belland and Crenn and approximately to the near and far field mode pattern theory of Degnan.     

电磁波在任意磁偏角等离子体中的传播

本文将电流密度卷积时域有限差分（Current Density Convolution Finite Difference Time Domain,JEC-FDTD）方法扩展到求解任意磁偏角电磁波在磁化等离子体中的传播和共振吸收问题.首先,验证数值算法正确性,分析了法拉第旋转角效应,以及任意磁偏角电磁波在等离子体中的传播特性.然后,求解电磁波在磁化等离子体中的等离子体朗缪尔共振、电子回旋共振、高频混杂共振吸收特性.结合在电离层加热中的应用,重点分析了等离子体高频混杂共振吸收特性,得到了高频混杂共振激发的频率匹配条件.数值结果表明,高频混杂共振吸收是电离层加热的有效方式,对于解释电离层加热机制具有重要意义.     

Electromagnetic wave propagation and wave-vector diagram in space-time periodic media

The electromagnetic wave propagation and wave-vector diagram in generally space-time periodic dielectric, plasma, and uniaxial plasma are studied for TE and TM waves. The case of a sinusoidal periodicity is solved numerically. Special properties due to the inhomogeneity are presented.     

Electromagnetic plane wave scattering by large and finite strip array on dielectric slab

Plane wave scattering from a large but finite strip array on dielectric substrate is analysed in the frequency domain via a decomposition into plane wave spectra by using the method of moments and a closed analytical form of the spectral Green’s function for the structure under examination. Closed form asymptotic expressions are developed for mutual coupling terms which lead to a highly efficient and accurate procedure. New results for radar cross section in the ultra-wideband frequency range of the finite strip array are shown. Influence of the resistivity of the strips in the variation of the radar cross section is noted and discussed. Variations of the radar cross section with the scattering angle are presented as well.     

Electromagnetic plane wave scattering by a system of two uniformlylossy dielectric prolate spheroids in arbitrary orientation

By means of modal series expansions of electromagnetic fields in terms of prolate spheroidal vector wave functions, an exact solution is obtained for the scattering by two uniformly lossy dielectric prolate spheroids in arbitrary orientation embedded in free space, the excitation being a monochromatic plane electromagnetic wave of arbitrary polarization and angle of incidence. Rotational-translational addition theorems for spheroidal vector wave functions are employed to transform the outgoing wave from one spheroid into the incoming wave at the other spheroid. The field solution gives the column vector of the unknown coefficients of the series expansions of the scattered and transmitted fields expressed in terms of the column vector of the known coefficients of the series expansions of the incident field and the system matrix which is independent of the direction and polarization of the incident wave. Numerical results in the form of curves for normalized bistatic and monostatic radar cross sections are given for a variety of two-body system of uniformly lossy dielectric prolate spheroids in arbitrary orientation having resonant or near resonant lengths and different distances of separation