A matrix‐exponential decomposition‐based time‐domain method for band structure calculation of one‐dimensional periodic structures

A time‐domain method for calculating the band structure of one‐dimensional periodic structures is proposed. During the time‐stepping of the method, the column vector containing the spatially sampled field data is updated by multiplying with an iteration matrix. The iteration matrix is first obtained by using the matrix‐exponential decomposition technique. Then, the small nonzero elements of the matrix are pruned to improve its sparse structure, so that the efficiency of the matrix–vector multiplication involved in each time‐step is enhanced. The numerical results show that the method is conditionally stable but is much more stable than the conventional finite‐difference time‐domain (FDTD) method. The time‐step with which the method runs stably can be much larger than the Courant–Friedrichs–Lewy (CFL) limit. And moreover, the method is found to be particularly efficient for the band structure calculation of large‐scale structures containing a defect with a very high wave speed, where the conventional FDTD method may generally lose its efficiency severely. For this kind of structures, not only the stability requirement can be significantly relaxed, but also the matrix‐pruning operation can be very effectively performed. In the numerical experiments for large‐scale quasi‐periodic phononic crystal structures containing a defect layer, significantly higher efficiency than the conventional FDTD method can be achieved by the proposed method without an evident accuracy deterioration if the wave speed of the defect layer is relatively high. Copyright © 2016 John Wiley & Sons, Ltd.     

Time‐domain sensitivity analysis of planar structures using first‐order one‐way wave‐equation boundaries

An efficient adjoint variable method technique is developed for time‐domain sensitivity analysis of planar structures with transmission‐line modeling complemented by a first‐order one‐way wave‐equation absorbing boundaries. A backward‐running adjoint simulation is derived and solved. The validity of the technique is illustrated through three microstrip circuits. The examples demonstrate the efficiency and accuracy of the technique in comparison with the classical finite‐difference approaches to the estimation of the response sensitivities. Copyright © 2007 John Wiley & Sons, Ltd.     

Forcing term discretization techniques in the external field‐to‐MTL coupling problems

In this paper, two, under certain conditions, equivalent models of electromagnetic plane wave coupling to multiconductor transmission lines (MTLs) are described. The ‘frequency‐to‐time domain’ (FTD) model incorporates the effect of the impinging electromagnetic waves by means of distributed voltage and current sources whose expressions are found through mathematical approximations made in the frequency domain followed by a transformation to the time domain. The approximations were made in order to gain an advantage in computation time in the discrete FTD (DFTD) model. In contrast to this approach, the same distributed sources of the ‘approximate analytic’ (AA) model are derived by directly evaluating the corresponding integral formulas. It is shown that, although the same second‐order‐accurate discretization technique has been employed to create both the DFTD and the discrete AA (DAA) models, the simulation results are not the same. In the case of the DFTD model, significant numerical error can be seen in the simulation results, whereas the DAA model does not show such a behaviour. It is shown that time averaging of the forcing terms in the DFTD model helps to reduce the numerical errors significantly at no extra computational cost. Copyright © 2001 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

Time‐frequency analysis of a pressure wave caused by impulse tree using wavelet transform

This paper describes results of time‐frequency analysis of a pressure wave caused by impulse tree extension using wavelet transform. Pressure waves were measured by a piezo sensor which was located on the back of the plane electrode when high‐voltage nanosecond pulses were applied to a point electrode in a low‐density polyethylene block. Frequency of the pressure wave from induced charges on the plane electrode was higher than that of the pressure wave from tree. In addition, the frequency of the pressure wave from tree tended to decrease with increasing gap length because of the dispersion of the pressure wave during its propagation. When a large tree extension occurred between a 5‐mm gap, pressure waves of about 10 MHz propagated from the tree tip and a pressure wave of 1 MHz propagated from the tree stem. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 1–7, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10097     

Dynamic C‐V characteristic for a varactor load connected with a transmission line

Crosstalk is induced by a reflected wave of a load connected with a transmission line. Thus, analysis of the reflected wave is important. The reflected wave generated from a nonlinear load is complicated. In order to estimate the complicated reflected wave, we measured the reflected and incident waves for the nonlinear load and estimated the dynamic C‐V characteristic, which explains the relation between the incident and reflected waves. This paper reports a simple experimental method of extracting reflected waves at a varactor load and presents estimates of the dynamic C‐V characteristic of the load. It is shown that the reflected voltage waves simulated using the dynamic C‐V characteristic agree with the measured results. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(4): 32–38, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20821     

Three‐dimensional numerical analysis on discharge properties of microwave excited ring dielectric line surface wave processing plasma device

A three‐dimensional simulation code with the finite difference time domain (FDTD) method combined with the electron fluid model has been developed for the microwave excited surface wave plasma in the RDL‐SWP device. This code permits the three‐dimensional numerical analysis of the spatial distributions of electric field, power absorption, electron density, and electron temperature. At a low gas pressure (about 10 mTorr), the numerical results were compared with the experimental measurements that show the validity of this 3D simulation code. A simplified analysis assuming that the electron density is spatially uniform has also been studied and its applicability is evaluated by the comparison of the 3D simulation and the analytical solutions. The surface wave eigenmodes are determined by the electron density, and it is found that the structure of the device strongly influences the spatial distribution of the electric fields of surface waves in a low‐density area (n_e < 3.0 × 10¹¹ cm^?3). A method to irradiate by microwave the whole surface area of the plasma is proposed. The method is found to be effective in obtaining a high uniformity distribution of electron density. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 150(4): 1–12, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10333     

Alpha-stable分布粗糙土壤表面电磁散射研究

采用空间域合成法生成高度起伏遵守Alpha-stable分布的粗糙土壤表面,运用矩量法研究了锥形入射波入射时粗糙土壤表面的电磁散射特性.数值计算了散射系数随散射角的变化关系,分析了稳定性系数、归一化尺度参数、互相关长度、入射波频率、土壤湿度对散射系数的影响.结果表明,稳定性系数、归一化尺度参数、互相关长度、入射波频率、土壤湿度对散射系数均有较大的影响,遵守不同的规律.     

A Green's function‐based method for the transient analysis of plane waves obliquely incident on lossy and dispersive planar layers

This paper presents a new methodology for the transient analysis of plane waves obliquely incident on a planar lossy and dispersive layer. The proposed model is based on the Sturm–Liouville problem associated with the propagation equations. Green's function is calculated in a series form and the open‐end impedance matrix is obtained as the sum of infinite rational functions. This form permits an easy identification of poles and residues. Furthermore, the knowledge of poles leads to the development of a model order reduction technique by selecting only the dominant poles of the system. The pole–residue representation is converted into a state‐space model that can be easily interfaced with ordinary differential equation solvers. The numerical results confirm the effectiveness of the proposed modeling technique. Copyright © 2008 John Wiley & Sons, Ltd.     

Implementation of the stretched co‐ordinate‐based PML for waveguide structures in TLM

A novel implementation of the stretched co‐ordinate‐based perfectly matched layer (SCB PML) is presented to terminate waveguide structures in transmission‐line modelling (TLM). A generalized SCB PML, the complex frequency shifted PML (CFS PML) is also implemented to investigate its performance for evanescent waves. State variables in the Z‐domain are employed to obtain update equations for incident voltage pulses. Numerical results for a rectangular waveguide filled with a lossy medium as well as free space, and for a parallel plate waveguide are presented. Copyright © 2004 John Wiley & Sons, Ltd.     

Global modeling of nonlinear circuits using the finite‐difference Laguerre time‐domain/alternative direction implicit finite‐difference time‐domain method with stability investigation

This paper describes a new unconditionally stable numerical method for the full‐wave physical modeling of semiconductor devices by a combination of the finite‐difference Laguerre time‐domain (FDLTD) and alternative direction implicit finite‐difference time‐domain (ADI‐FDTD) approaches. The unconditionally stable method by using FDLTD scheme for the electromagnetic model and semi‐implicit ADI‐FDTD approach for the active model leads to a significant decrease in the full‐wave simulation time. Numerical simulations of an example transistor and a power amplifier show the efficiency of presented method for the full‐wave simulation of mm‐wave active circuits. Copyright © 2012 John Wiley & Sons, Ltd.     

A generalized CAD model for the full‐wave modeling of Coplanar striplines discontinuities

In this work, the coplanar stripline (CPS) and its discontinuities: open‐end, short‐end, gaps and resonator have been modeled. New integral equations for the electrical field components are formulated, in the spectral domain, using an exact dyadic Green's function, applied to the CPS structure. The use of this form of Green's function allows the consideration of the effects of the dielectric losses, the surface wave excitation and the space wave radiation on the propagation characteristics of the CPS and its discontinuities. The resulting integral equation has been solved using the two‐dimensional Galerkin's technique. The resolution of the resulting matrix equation gives the scattering parameters of the studied structures. The obtained results are commented and compared with those of other approaches and measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Square‐root domain wave filters

In this paper the wave method is used for designing high‐order square‐root domain filters, which emulate the topology of the corresponding LC ladder prototypes. This is achieved by transposing the signal flow graph that corresponds to the wave equivalent of the elementary two‐port subnetwork in the linear domain to the corresponding one in the square‐root domain, by employing an appropriate set of complementary operators. As the equivalents of the other reactive elements are derived from the wave equivalent of the elementary subnetwork, by interchanging the terminals of the appropriate wave signals and/or using inverters, an advantage offered by the proposed technique is the modularity of the derived filter configurations. As an example, a fifth‐order lowpass square‐root domain wave filter was designed and its behaviour was studied through simulation results in order to demonstrate the validity of the proposed design technique. Copyright © 2006 John Wiley & Sons, Ltd.     

Scattering characteristics of FSSs with triangular conducting elements

In this paper, scattering characteristics of dielectric backed frequency selective surfaces (FSSs) having triangular conducting elements are investigated for both transverse magnetic and transverse electric incident plane waves. Since triangular conducting elements are etched periodically on such a surface, incident and scattered fields are expressed as Floquet modes. Using Floquet’s theorem and satisfying the required boundary conditions an integral equation is obtained for the induced current density on the surface of a triangular conducting element in one periodic cell. This induced current density is expressed as a finite sum of piecewise triangular basis functions having unknown coefficients. The resulting integral equation is then converted to a linear matrix equation by using the Method of Moments. Taking the inverse transform of the matrix equation yields the unknown current coefficients which are finally used to compute the reflection and transmission coefficients. Since there are no theoretical or experimental results for FSSs comprising of triangular conductors, verification of the algorithm developed is carried out by comparing the numerical results obtained using this algorithm with the experimental and theoretical results in the literature for FSSs composed of strips and L-shaped conductors. For this, in the algorithm, appropriate arms of the triangles are removed to conform them into strips or L-shaped conductors. Results obtained for strips and L-shaped apertures by using this algorithm are in excellent agreement with the results in the literature.     

Electromagnetic‐circuit co‐simulation of very fast transient overvoltage in gas‐insulated switches

The very fast transient overvoltage (VFTO) originating from operations of an isolating switch in a gas‐insulated switch (GIS) will cause dangerous interference to the switch and its peripherals. Aiming at the engineering issue, a collaborative simulation method by field‐circuit‐wave of VFTO radiation interference is proposed in this paper. With a combination of project cases, the GIS equivalent circuit is first extracted by means of quasistatic electromagnetic (EM) field analysis. Furthermore, the equivalent time‐varying voltage source of VFTO is obtained by associating the time‐varying resistance model of the switching arc and the broadband circuit method. Finally, using the transient full‐wave technique in the time domain, the spatial EM interference by VFTO is simulated. It turns out that this method has high significance to the high‐voltage switch design. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Untersuchung des Reflexions- und Transmissionsverhaltens an einem verlustbehafteten Halbraum im Zeitbereich

Übersicht Das Reflexions- und Transmissionsverhalten einer ebenen Grenzfläche zwischen einem Isolator und einem verlustbehafteten Halbraum wird für senkrecht einfallende ebene TEM-Wellen mit beliebiger Wellenformfunktion analytisch im Zeitbereich untersucht. Die reflektierten und durchgehenden Teilwellen werden danach für eine impulsförmige Wellenformfunktion der einfallenden Welle spezialisiert. Aufgrund der Verluste entstehen kontinuierliche Feldanteile. Für die Aufteilung und Ausbreitung der impulsförmigen Feldanteile gelten ganz elementare Zusammenhänge. Durch geeignete Normierungen lassen sich die Feldlösungen sehr allgemein verwenden und auch auf leitungsgebundene Wellen anwenden.

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Investigation of the reflection and transmission properties of a lossy half space in time domain

Contents The reflection and transmission of a plane TEM-wave with arbitrary wave shape which is perpendicular incident on a planar interface between a perfect dielectric and a lossy semi-infinite medium is analytically investigated in the time domain. In addition the reflected and transmitted waves are calculated for incident impulse waves. Due to the losses, continuous terms evolve. The distribution and the propagation of the impulse-shaped parts can easily be described. Because of appropriate normalisation, the field solutions are very flexible and can also be used for transmission lines.

     

Sleeve monopole on a circular ground‐plane

This paper presents a modal‐expansion analysis of a sleeve monopole antenna on a finite ground‐plane. Two perfectly conducting plates (one above the monopole and the other under the ground‐plane) are introduced to confine the modeling region and to facilitate the modal‐expansion analysis. The resulting guided‐wave structure is then divided into a number of regions and the electromagnetic field components in each region are expanded into the summation of its modal functions. The surface current distribution on the monopole and the antenna's input impedance and radiation pattern are obtained by finding the expansion coefficients through matching the tangential field components across the regional interfaces. Calculated results by the modal‐expansion method agree well with measured results for the return loss of a sleeve monopole fed through a circular ground‐plane by a coaxial probe. Numerical results for the surface current distribution, input impedance, and radiation pattern of a sleeve monopole on a circular ground plane are presented and discussed. Copyright © 2003 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.     

A GSM analysis of E‐plane waveguide junctions filled with piecewise homogeneous dielectric

A specific generalized scattering matrix (GSM) approach to the analysis of a piecewise homogeneous E‐plane waveguide junction with plane interfaces is presented. The object is cascaded into homogeneously filled regions, whose GSMs are found in solving two uncoupled scalar problems related to longitudinal section electric and magnetic modes, and interfaces responsible for interaction of the said modes. The GSMs of irregular constituents are determined with the help of triangular blocks. Scattering parameters of the last ones are obtained by means of the domain‐product technique. The approach was successfully verified via test problems and was applied to the analysis of scattering of the TE₁₀ mode by an E‐plane slant interface between two dielectric media. Copyright © 2011 John Wiley & Sons, Ltd.     

A frequency‐domain‐based master stability function for synchronization in nonlinear periodic oscillators

An efficient methodology to study conditions for stable in‐phase synchronization in networks of periodic identical nonlinear oscillators is proposed. The problem of investigating synchronization properties on periodic trajectories is reduced to an eigenvalue problem by means of the joint application of master stability function and harmonic balance techniques. The proposed method permits to exploit the periodicity of trajectories, reducing computational time with respect to traditional time‐domain approaches (which were designed to deal with generic attractors) and good accuracy. In addition, such method can easily deal with networks of nonlinear periodic oscillators described by differential‐algebraic equations, and then both static and dynamic coupling could be studied. Copyright © 2011 John Wiley & Sons, Ltd.     

Full‐wave modelling of microstrip line and its sensitivities on lossy multilayer dielectric substrate and superstrate with laminated ground plane

This paper presents a new formulation useful for modelling multilayered microstrip and its geometrical sensitivities with laminated ground plane. New integral equations are formulated, in the spectral domain, using the exact dyadic Green's function of bianisotropic planar media. We have applied a dynamic two‐dimensional least‐square algorithm as an optimization procedure. Obtained results agree well with those of other approaches. Copyright © 2002 John Wiley & Sons, Ltd.