TLM simulation of electromagnetic wave propagation in anisotropic moving media

A transmission line matrix (TLM) model suitable to simulate the propagation of waves in moving anisotropic continuous media is presented. As is well known, an electromagnetic wave propagating in a general medium, moving with respect to its source, experiences a drag by the own medium, which involves a wave velocity dependent on the direction of propagation. In this work, we present a first approach for the case of uniform movement of an anisotropic dielectric medium with respect to an electromagnetic source. Although the technique allows for quantitative results, special attention is devoted to the simulation of wave fronts, distorted elliptical fronts, because a particular kind of ‘anisotropy’ appears, even in an isotropic medium. Copyright © 2005 John Wiley & Sons, Ltd.     

On the development of efficient FDTD‐PML formulations for general dispersive media

A novel implementation of the perfectly matched layer (PML) absorbing boundary condition (ABC) to terminate the finite‐difference time‐domain (FDTD) algorithm for general dispersive and negative index materials is presented. The proposed formulation also adopts the complex frequency‐shifted (CFS) approach, involves simple FDTD expressions and avoids complex arithmetic. Several FDTD‐PML simulations with different parameters are conducted for the termination of various dispersive media validating the stability, accuracy and effectiveness of the schemes and indicating the advantage of the CFS‐PML. Copyright © 2008 John Wiley & Sons, Ltd.     

Modeling of doubly lossy and dispersive media with the time‐domain finite‐element dual‐field domain‐decomposition algorithm

A numerical scheme is presented for the time‐domain finite‐element modeling of an electrically and magnetically lossy and dispersive medium in the dual‐field domain‐decomposition method. Existing approaches for modeling doubly lossy and dispersive media are extended to the dual‐field case, yielding a general dual‐field domain‐decomposition scheme for modeling large‐scale electromagnetic problems involving such media. A quantitative analysis is performed to estimate the error induced by the modeling of medium dispersion. Copyright © 2012 John Wiley & Sons, Ltd.     

Numerical study of electromagnetic wave propagation through layered structures with chiral media

In this paper, the characteristics of layered structures (photonic or electromagnetic bandgaps), including chiral media, are studied by means of two different numerical methods, one in the time domain (finite differences in the time domain, FDTD) and the other in the frequency domain (coupled‐mode method, CMM). The results (reflection and transmission coefficients for a plane wave normally incident over a layered structure) obtained by means of both well different techniques are practically identical. Copyright © 2009 John Wiley & Sons, Ltd.     

Simplified analysis techniques for VLF wave propagation in the earth–ionosphere waveguide

VLF (very low frequency; 3 to 30 kHz) wave propagation in the earth–ionosphere waveguide can be simply analyzed by the method developed in this paper. The finite‐di?erence time‐domain (FDTD) method is used with a conductivity tensor to model the ionosphere, and the applicability is limited to monotonic cases. The proposed method is compared with the wideband method, and it is concluded that the newly developed method can be used as a VLF wave simulator without errors. Conformal FDTD is also introduced to allow for the curvature of the earth's surface, and we have clarified the di?erence between two‐dimensional modeling in Cartesian coordinates and cylindrical coordinates. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 25–31, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22302     

An accurate time‐domain model of transmission lines with frequency‐dependent parameters

Linear lossy two‐conductor transmission line can be modelled as dynamic two ports in the time domain, via the describing input and transfer impulse responses. This convolution technique is very effective when dealing with networks composed of transmission lines with frequency‐dependent parameters and non‐linear and/or time‐varying circuits. The paper carries out an accurate analysis of this model, in the most general case of lines with frequency‐dependent parameters. For such lines it is not possible to evaluate analytically the impulse responses, nor is it possible to catch them numerically, due to the presence of irregular terms, such as Dirac pulses, terms that numerically behave as Dirac pulses, and functions of the type 1/t^ρ with 0 < ρ <1. A simple method is proposed to evaluate exactly all the irregular terms of the impulse responses: once these irregular parts have been extracted, the regular remainders are easily evaluated numerically. This method is applied to analyse lines with frequency‐dependent parameters of practical interest, such as superconductor transmission lines, power lines above a finite conductivity ground, lines with frequency‐dependent dielectric losses and lines with normal and anomalous skin‐effect. Numerical simulations are carried out for illustration. Copyright © 2000 John Wiley & Sons, Ltd.     

Measurements of electromagnetic surface wave propagation in the cut‐off frequency region

Electromagnetic surface wave propagation on a corrugated metal plate is confirmed by a cold test in the X‐band. The measured cut‐off frequency is almost in agreement with the theoretical cut‐off frequency. The propagation is damped at a frequency region higher than the cut‐off frequency. The periodicity of the propagation power to the frequency is confirmed. For the confirmation of these characteristics, it is necessary that the corrugated metal plate is enclosed within a microwave absorber. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Simulation of EM wave propagation in magnetoelectric media using TLM

In this paper, the simulation of general frequency‐dependent magnetoelectric material properties in time‐domain TLM is described. The formulation is developed from Maxwell's equations and the constitutive relations using bilinear 𝒵‐transform methods leading to a general Padé system. The approach is applicable to all frequency‐dependent linear materials including those displaying anisotropic and bianisotropic behaviour. The method is validated by the example of a chiral slab having an analytic solution. Copyright © 2001 John Wiley & Sons, Ltd.     

The effect of media parameters on wave propagation in a chiral metamaterials slab using FDTD

Because the permittivity, permeability, and chirality parameters of chiral metamaterials (CMMs) are frequency dependent, the wave equations that describe the characters of electromagnetic wave propagation in CMMs are presented and discretized on the basis of auxiliary differential equation technique in finite‐difference time‐domain method. The total‐field/scattered‐field, Mur's first‐order absorbing and dielectric boundary conditions for CMMs slab are discussed in the paper. Numerical results show that the cross‐polarized reflected coefficient of the CMMs slab is zero. Negative index of refraction phenomenon and optical property of giant optical activity in CMMs slabs are illustrated with 1D auxiliary differential equation–finite‐difference time‐domain method. The effects to positive or negative phase velocity caused by media parameters of CMMs are studied. Copyright © 2013 John Wiley & Sons, Ltd.     

Dispersive TLM Z‐transform model of left‐handed metamaterials

In this paper, a numerical model of electromagnetic left‐handed metamaterials is proposed. The dispersive properties of these materials are accounted for in the time domain by using the transmission‐line matrix method based on Z‐transforms. The close agreements obtained between the analytic and numerical results verify the validity, accuracy and stability of the approach. Copyright © 2013 John Wiley & Sons, Ltd.     

Consideration of radiated electromagnetic waves from partial discharge based on half‐wave dipole antenna model

Partial discharge (PD) may take place due to residual defects like metallic particles in SF₆ gas‐insulated power apparatus such as GIS. However, the signal of PD occurring in SF₆ gas is very weak and susceptible to external noise in air. Moreover, because of the complicated mechanism of PD, the radiation property of electromagnetic waves from PD has not as yet been clarified. Therefore, it is hard to distinguish the PD signal in SF₆ gas from external noise. From the above points of view, we have been investigating the radiation mechanism of electromagnetic waves from PD. We measured the polarization characteristics of electromagnetic waves radiated from PD in comparison with those of half‐wave dipole antennas. The polarization characteristics of PD were explained by the theory of half‐wave dipole antenna, rather than that of an infinitesimal dipole antenna. Moreover, we compared the power spectrum for PD measured using a biconical antenna with that received from the half‐wave dipole antenna or infinitesimal dipole. It was found that the power spectrum for PD also corresponded to that for the half‐wave dipole antenna with a length of 50 cm. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 40–47, 1999     

无线通信系统中电波传播路径损耗模型研究

通过对无线通信系统中电波传播的无线信道分析,介绍了电波传播路径损耗预测的各种模型,重点研究了电波传播路径损耗的室外宏蜂窝模型中的Hata模型、Walgish-Ikegami模型和室内的Motley模型,并对室外的宏蜂窝模型进行了仿真,从而为无线通信系统电波传播信道的设计与规划提供了理论基础.     

声波在锅炉换热器管阵列中的传播特性研究

基于对炉内单排和双排换热器管阵列声传播特性的研究基础,分析多排管阵列对声波的反射、透射和衍射机理;利用数学推理方法和迭代过程给出计算炉内多排管阵列声透射与反射系数的数学模型,研究多排换热器管阵列的声透射特性,揭示炉内多排管阵列的声反射与透射系数随声波频率、管排数和管阵列结构参数的变化关系;并在炉内实际温度下对声透射系数进行数值计算,为锅炉管道泄漏检测技术提供理论依据.     

FDTD simulation of nonlinear ultrasonic pulse propagation in ESWL using equations including Lagrangian

A new FDTD algorithm is proposed for analyzing ultrasonic pulse propagation in the human body, a problem connected with ESWL (extracorporeal shock wave lithotripsy). In this method, we do not use plane wave approximation but directly employ the original equations, taking into account the Lagrangian to derive new FDTD algorithms. This method is applied to an experimental setup and its numerical model that resembles an actual treatment situation in order to compare the sound pressure distributions obtained numerically with those obtained experimentally. The present method is shown to give clearly better results than the earlier method, from the point of view of the numerical reappearance of a strongly nonlinear waveform. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(4): 29–36, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20819     

Full‐wave analysis of traveling pulses developed in a system of transmission lines with regularly spaced resonant‐tunneling diodes

In a system of transmission lines with regularly spaced resonant‐tunneling diodes (RTDs), where several straight RTD lines are connected halfway to a closed RTD line, a pulse‐shaped rotary traveling wave develops on the closed line by mutual synchronization of the oscillatory edge developed in each straight RTD line. The oscillating edge on each straight line is synchronized with the traveling pulse, such that the system has the potential to generate multiphase oscillatory signals in millimeter‐wave frequencies. To examine the dynamics of traveling pulses at such high frequencies, the system is modeled in the framework of the finite‐difference time‐domain method. It is found that a traveling pulse develops in the closed RTD line synchronized with the oscillatory edges moving in the straight lines, assuming a microstrip structure for each RTD line. We then compare the results of the finite‐difference time‐domain calculation with those predicted by the transmission line theory with parameter values obtained by the quasi‐transverse electromagnetic estimation. In addition, the RTD line that compactly confines the electromagnetic fields is shown to have the potential to generate multiphase oscillatory signals at submillimeter‐wave frequencies.     

Time domain global modelling of EM propagation in semiconductor using irregular grids

A two‐dimensional finite volume time domain (FVTD) method using a triangular grid is applied to the analysis of electromagnetic wave propagation in a semiconductor. Maxwell's equations form the basis of all electromagnetic phenomena in semiconductors and the drift‐diffusion model is employed to simulate charge transport phenomena in the semiconductor. The FVTD technique is employed to solve Maxwell's equations on an irregular grid and the finite box method is implemented on the same grid to solve the drift‐diffusion model for carrier concentration. The locations of unknowns have been chosen to allow linking coupled Maxwell's equations and transport equations in a seamless way. To achieve suitable accuracy and computational efficiency, using irregular grid topology allows a finer mesh in doped region and at junction, and a coarser mesh in substrate and insulting regions. The proposed scheme has been implemented and verified by characterizing electromagnetic wave propagation at microwave frequency in a semiconductor slab with arbitrary doping profile. Copyright © 2002 John Wiley & Sons, Ltd.     

Analysis of high frequency performance of TO‐46 header through three‐dimensional full wave electromagnetic model and circuit model

The TO‐46 header has been commonly used for vertical cavity surface emitting laser (VCSEL) and photodetector package. The high‐frequency characteristics of a TO‐46 header were measured using our special K‐type adaptors and simulated through a three‐dimensional full wave electromagnetic simulator. The measurement and simulation results show the TO‐46 header provides a resonance‐free transmission bandwidth over 40‐GHz and reflection loss below −10‐dB within 31‐GHz, with an ideal 50‐Ω terminal. The 25‐Gb/s and 40‐Gb/s eye diagrams through a TO‐46 header were measured using our measurement setup, and the eye diagrams are clear enough. In addition, the single‐end and differential‐end equivalent circuit models of a TO‐46 header were established and verified. The TO‐46 header provides a low‐cost and high‐speed package solution and can be applied in 21‐Gb/s fiber channel technology and 100‐Gb/s (4 × 25‐Gb/s) Ethernet (100 GbE) network. Copyright © 2015 John Wiley & Sons, Ltd.     

A note on global convergence of adaptive control in a discrete‐time non‐linear case

Adaptive control is applied to a particular class of SISO discrete‐time non‐linear systems. Global boundedness and convergence are obtained by introducing a modification to a classical adaptive scheme. Copyright © 1999 John Wiley & Sons, Ltd.     

Adaptive control of discrete‐time nonlinear systems by recurrent neural networks in quasi‐sliding mode like regime

The aim of this study was to design an adaptive control strategy based on recurrent neural networks (RNNs). This neural network was designed to obtain a non‐parametric approximation (identification) of discrete‐time uncertain nonlinear systems. A discrete‐time Lyapunov candidate function was proposed to prove the convergence of the identification error. The adaptation laws to adjust the free parameters in the RNN were obtained in the same stability analysis. The control scheme used the states of the identifier, and it was developed fulfilling the necessary conditions to establish a behavior comparable with a quasi‐sliding mode regime. This controller does not use the regular form of the switching function that commonly appears in the sliding mode control designs. The Lyapunov candidate function to design the controller and the identifier simultaneously requires the existence of positive definite solutions of two different matrix inequalities. As consequence, a class of separation principle was proven when the RNN‐based identifier and the controller were designed by the same analysis. Simulations results were designed to show the behavior of the proposed controller solving the tracking problem for the trajectories of a direct current (DC) motor. The performance of the proposed controller was compared with the solution obtained when a classical proportional derivative controller and an adaptive first‐order sliding mode controller assuming poor knowledge of the plant. In both cases, the proposed controller showed superior performance when the relation between the tracking error convergence and the energy used to reach it was evaluated. Copyright © 2016 John Wiley & Sons, Ltd.     

Threshold computation for fault detection in a class of discrete‐time nonlinear systems

In this paper, we address the problem of designing robust thresholds for fault detection in discrete‐time nonlinear uncertain systems in the presence of process disturbances. Both constant and dynamic thresholds are proposed. For the computation of constant thresholds, a generalized framework based on signal norms is developed. Different kinds of constant thresholds are studied in the framework proposed. Using linear matrix inequalities (LMI) techniques, algorithms are derived for the computation of these thresholds. Similarly, the dynamic threshold is designed by deriving an inequality on the upper bound of the modulus of the residual signal. This inequality is based on the solution of discrete‐time nonlinear uncertain systems. The simulation examples illustrate that false alarms are successfully eliminated using the proposed thresholds. Copyright © 2010 John Wiley & Sons, Ltd.