Reflection and transmission characteristics of lossy periodiccomposite structures

A periodic surface integral formulation is proposed to analyze the reflection and transmission properties of a lossy periodic composite structure which has circular conducting fibers embedded in a dielectric matrix. This formulation is based on the equivalence principle which represents the unknown electric and magnetic currents over the material discontinuity interfaces, and uses the structure periodicity and Poisson summation formula to reduce the problem to a periodic cell. These surface integral equations are then solved numerically, using the method of moments with pulse bases and point matching. Only the transverse magnetic (TM) case is analyzed and the numerical results such as reflected, transmitted, and dissipated powers for a single-layer fiber-reinforced composite structure are presented, in detail, to discuss the effects of frequency, incident angle, fiber radius, fiber conductivity, embedding dielectric, etc. A convergence study and a comparison with the previous published results are also included to confirm the accuracy of the new formulation     

Reflection and transmission characteristics of an uncoincidentaljunction on rectangular dielectric waveguides

A novel approach to the analysis of an uncoincidental junction in a rectangular dielectric waveguide is presented. The boundary condition equations on the junction plane are presented through the tangential components of guided modes and radiation modes which are excited at the discontinuity. To obtain the reflection and transmission coefficients at the discontinuity, the equations are transformed into the spectral domain by the two-dimensional Fourier transformation. In the spectral domain, the orthogonal relationship between the guided and radiation modes is used to determine the reflection and transmission coefficients approximately. The parameters corresponding to the phase constant of the radiation fields in the spectral domain are defined by using an iterative calculation. The reflection and transmission coefficients are determined exactly. These coefficients are compared with 10-GHz band experiments. The analysis shows good agreement with experimental results     

Reflection and transmission characteristics of a slab with periodically varying surfaces

Using a plane wave spectral decomposition of the relevant electromagnetic (EM) fields and the T-matrix solution philosophy, a T-matrix is formulated which completely characterizes the EM response of an infinite material plate bounded by two homogeneous half-spaces, the two interfaces being periodically rough. Individual T-matrices for either of the two periodic bimaterial interfaces are used in this derivation. Using the computed results, the anomalies in the scattering response of the rough slab are explained in terms of reflectionless and transmissionless modes, the Brewster angle, and the conditions for propagation or evanescence of a given plane wave mode.     

电磁波在媒质分界面上的反射与透射特性

由于不同媒质的参数不同,电磁波入射到媒质分界面会产生反射和透射现象.通过对电磁波在分界面上反射和透射的理论分析,讨论了反射波透射波振幅、方向随入射角的变化特性.     

微结构光子晶体光纤中的TE模传输

通过光子能带带隙和传输模式的数值模拟分析,研究了空芯和实芯微结构光子晶体光纤中,横电模TE作为基模传输的可能性,得出了TE模作为基模传输的基本条件为：只有当光纤包层第二禁带部分落在纤芯折射率分界线以上时,才能保证将光束缚在纤芯中传输,同时其传输的基模才是横电模TE;若在包层第一禁带,其传输的将是混合模HE11。     

光纤复合低压电缆温度分布与光单元传输特性研究

研究线缆发热与光单元传输特性变化之间的关系对光纤复合低压电缆(OPLC)设计及应用十分重要。用COMSOL软件模拟仿真光纤复合低压电缆的稳定运行和短路故障状态,得到其相应的电缆温度分布以及光单元传输损耗特性。选取线缆上不同位置处的特征点进行仿真,结果表明：电缆故障时导体绝缘层内升温较明显,外护套温度变化不明显;光纤温度变化很小,其温度在5 s内只有0.2 ℃的上升。由热膨胀引起的位移很小,使得传输损耗在这2种情况下几乎一样,短路故障对光纤的温度影响不大。设计光单元升温实验得到光缆传输损耗的数据,并与仿真数据进行对比分析。实测温度数据滞后于仿真数据5 s,但与仿真数据变化趋势一致,证明了仿真模型的可靠性和可行性。     

Operating characteristics of TE copper bromide lasers

Detailed operating characteristics of transversely excited (TE) double-pulse copper bromide lasers employing discharge stabilization techniques are reported. With careful optimization of operating temperature, buffer gas pressure, dissociation and excitation energies, and pulse delay times, specific output energies up to 35μJ/cm³have been obtained for a device of active volume 150 cm³. The nature of the dominant processes influencing ground state and metastable copper atom densities in the interpulse region are discussed in terms of the observed effects of temperature and gas pressure on the characteristic delay times.     

Calibrated Reflection Coefficient Standards for the Circular TE/sub 01/ Mode

This paper describes simple reflection coefficient standards for use with the circular TE/sub 01/ mode. They consist of circular irises inserted directly into the flange connection of a "matched" termination. The reflection coefficient of an iris is formulated exactly and then evaluated to any desired degree of approximation with a digital computer. The results of a 30-mode approximation are presented and shown to agree with 24 GHz measurements of the modulus and phase of /spl rho/ of 7 irises to within about 0.008 relative units and 0.02 radians, respectively.     

透射全息图的反射象成因分析

本文从实验结果出发,比已有的文献更全面地分析了透射全息图的反射象的成因。     

传输线的反射干扰

在数字信号处理系统中,时钟信号和数字信号传输因传输始端和终端阻抗不匹配而引起反射干扰,使传输信号的波形出现上冲、下降和振荡。为了抑制这种因阻抗不匹配引起的反射,本文首先从产生这种反射的原因和造成的重大危害分析,提出了反射干扰这一亟待解决的问题;接着从传输线的阻抗特性以及阻抗匹配原理出发,提出了始端和终端阻抗匹配原则,最后给出了几种减小和抑制反射干扰的方法,实践证明使用阻抗匹配这一方法在减小反射干扰是十分有效的。     

TE and TM modes in cylindrical metallic structures filled withbianisotropic material

Modal propagation is studied for metallic circular waveguides, coaxial cables and sectoral waveguides filled with linear bianisotropic material. By representing the material constitutive tensors in cylindrical coordinates, the conditions under which TE and TM modal decoupling occurs are obtained, and second-order differential equations for the longitudinal field components are derived. Though the TE and TM longitudinal field components are expressible in terms of hypergeometric functions, a complete numerical solution scheme is, in general, more convenient. Conventional application of finite elements renders the differential problem numerically equivalent to a generalized eigenvalue matrix problem, whose solution yields the dispersion relation and cutoff frequencies of the waveguides together with the eigenfields expression. The effects one can obtain by varying the various coefficients of the constitutive tensors are illustrated by several numerical results     

Verification structures for transmission line pulse measurements

Test structures intended for performance verification of transmission line pulse (TLP) systems have been designed and tested. They consist of simple resistors in either copper or silicide clad polysilicon. The copper structures proved unsuitable due to excess heating and melting of any reasonable geometry. The silicide clad polysilicon proved more successful. A simple model of resistive heating accounts for observed nonlinearity in the structures under high current stress. The availability of a verification structure on wafer ensures the proper performance of the full measurement system, including contact to the wafer and the pad structure, ensuring valid TLP measurements.     

Characteristic modes for slots in a conducting plane, TE case

Consider an infinitely long slot in a perfectly conducting plane in an unbounded medium illuminated by a uniform transverse electric (TE) (to the slot axis) plane wave. The theory of characteristic modes for apertures is applied to solve the problem. For a narrow slot, analytic expressions for the first two characteristic currents and the equivalent magnetic current are given. As computed by the method of moments, numerical results for the characteristic currents and fields, the equivalent magnetic current, and the transmitted field pattern are presented for the slot whose width is one wavelength.     

Reflection and transmission of a dielectric waveguide mirror

A numerical analysis of a generalized dielectric waveguide mirror of arbitrary structure angle is presented. A plane wave expansion technique is used to calculate output angle, power transmission, inter-waveguide and intra-waveguide coupling, far-field emission profile and losses of the waveguide mirror. In order to evaluate the effect of divergence, two methods are used and the result indicate that the effect is minimal. Furthermore, the introduction of a tilt in the mirror surface is examined and reveals a reduction in the inter-waveguide coupling as the tilt is increased. However, this coupling remains symmetric in tilt despite the asymmetry of the geometry due to the tilt. Results of the output angle and the FWHM (full-width half-maximum) of the emission profile are compared to experimental values obtained for a semiconductor triangular ring laser     

Measurements of reflection and transmission characteristics ofinterior structures of office building in the 60-GHz band

We have measured (at 57.5 GHz) the reflection and transmission coefficients of typical walls, floor, ceiling, window, and partitions and have compared the measured reflection characteristics with the reflection characteristics estimated by multilayer dielectric models. Although the positional inhomogeneity of structures gives rise to some variation from one measured position to another, these positional variabilities are not large. The overall trend of reflection coefficients calculated by multilayer dielectric models thus agrees fairly well with the trend of the measurements. We have shown that the use of circular polarization can reduce the reflection even if the interior parts of the structure have complicated structures. In addition, the shadowing effects of several types of partitions were measured. The transmission coefficients of partitions depend on the materials. The transmission losses of plywood-made partitions are found to be fairly low     

Reflection and transmission coefficients of a thin strip grating for antenna application

Reflection and transmission coefficients of thin strip gratings are discussed for plane wave incidence from arbitrary direction. Upon use of the low-frequency approximation, simple closed-form expressions are obtained. They are applicable for the analysis of grid reflector antennas. Physical interpretations of the phenomena are also given and interesting characteristics of the gratings are pointed out. The validity and the applicability of our results is examined numerically by making use of the point matching method (PMM). It is shown that the accuracy is excellent provided the period of gratings is smaller than about 0.3 wavelength.     

Comparative performance of pyramid data structures for progressiveimage transmission

A review of various pyramid data structures for progressive image transmission, focusing on the steps involved in forming the pyramid and the performance comparisons, is presented. The simple mean pyramid, its variants including the truncated mean, reduced-sum, difference, reduced-difference and S-transform pyramids, and the more general Laplacian pyramid are discussed. It is also shown that the use of an interpolation function improves the quality of the full-resolution approximations both objectively and subjectively     

Reflection and transmission coefficients of a periodic dielectric slab

The plane-wave reflection and transmission coefficients of a dielectric slab having a sinusoidal variation of its permittivity are deduced from the solution of the full electromagnetic boundary-value problem and compared with the results of the approximate procedure based on the coupled-mode equations for the slowly varying amplitudes.     

Reflection and transmission coefficients for backward waves on a corrugated YIG film

The reflection and transmission coefficients for the backward magnetic waves on a YIG film with periodic surface corrugations are systematically deduced from the solution of the full magnetostatic boundary-value problem. The phenomenological boundary condition for the slowly varying amplitude in the coupled mode equations is also obtained.     

A fast high-order solver for EM scattering from complex penetrablebodies: TE case

We present a new high-order integral algorithm for the solution of scattering problems by heterogeneous bodies under TE radiation. Here, a scatterer is represented by a (continuously or discontinuously) varying refractive index n(x) within a two-dimensional (2-D) bounded region. Solutions of the associated Helmholtz equation under given incident fields are then obtained by high-order inversion of the Lippmann-Schwinger integral equation. The algorithm runs in O(N log(N)) operations, where N is the number of discretization points. Our method provides highly accurate solutions in short computing times, even for problems in which the scattering bodies contain complex geometric singularities