A waveguide 2-plane hybrid coupler with two operating bands is proposed. The cross-sectional shape of the coupled region inside the proposed coupler is designed with a two-dimensional arbitrary geometry sorting method. Simulations of the proposed hybrid coupler has a fractional bandwidth (FBW) of 2.17% at the center of 24.99GHz, and at the center of 28.28GHz an FBW of 6.13%. The proposed coupler is analyzed by the mode-matching finite-element hybrid method, and the final result is obtained using a genetic algorithm. The analyzed result of the coupling for the main modes in the coupled region is presented. The design result is confirmed by measurements.

In order to increase communication capacity, the use of millimeter-wave and terahertz-wave bands are being actively explored. Non-radiative dielectric waveguide known as NRD guide is one of promising platform of millimeter-wave integrated circuits thanks to its non-radiative and low loss nature. In order to develop millimeter wave circuits with various functions, various circuit components have to be efficiently designed to meet requirements from application side. In this paper, for efficient design of NRD guide devices, we develop a topology optimal design technique based on function-expansion-method which can express arbitrary structure with arbitrary geometric topology. In the present approach, recently developed two-dimensional full-vectorial finite element method (2D-FVFEM) for NRD guide devices is employed to improve computational efficiency and several evolutionary approaches, which do not require appropriate initial structure depending on a given design problem, are used to optimize design variables, thus, NRD guide devices having desired functions are efficiently obtained without requiring designer's special knowledge.

In this paper, we reformulate a sensitivity analysis method for function-expansion-based topology optimization method without using gray area. In the conventional approach based on function expansion method, permittivity distribution contains gray materials, which are intermediate materials between core and cladding ones, so as to let the permittivity differentiable with respect to design variables. Since this approach using gray area dose not express material boundary exactly, it is not desirable to apply this approach to design problems of strongly guiding waveguide devices, especially for plasmonic waveguides. In this study, we present function-expansion-method-based topology optimization without gray area. In this approach, use of gray area can be avoided by replacing the area integral of the derivative of the matrix with the line integral taking into acount the rate of boundary deviation with respect to design variables. We verify the validity of our approach through applying it to design problems of a T-branching power splitter and a mode order converter.

The accurate calculation of the inductance is the most basic problem of the inductor design. In this paper, the core flux density distribution and leakage flux in core window and winding of core-type inductor are analyzed by finite element analysis (FEA) firstly. Based on it, an improved magnetic equivalent circuit with high accuracy flux density distribution (iMEC) is proposed for a single-phase core-type inductor. Depend on the geometric structure, two leakage paths of the core window are modeled. Furthermore, the iMEC divides the magnetomotive force of the winding into the corresponding core branch. It makes the core flux density distribution consistent with the FEA distribution to improve the accuracy of the inductance. In the iMEC, flux density of the core leg has an error less than 5.6% compared to FEA simulation at 150A. The maximum relative error of the inductance is less than 8.5% and the average relative error is less than 6% compared to the physical prototype test data. At the same time, due to the high computational efficiency of iMEC, it is very suitable for the population-based optimization design.

The electromagnetic interference (EMI) generated by power electronic converters is largely influenced by parasitic inductances and capacitances of the converter. One of the most popular EMI simulation methods that can take account of the parasitic parameters is the three-dimensional electromagnetic simulation by finite element method (FEM). A noise-source model should be given in the frequency domain in comprehensive FEM simulations. However, the internal impedance of the noise source is static in the frequency domain, whereas the transient switching of a power semiconductor changes its internal resistance in the time domain. In this paper, we propose the use of a voltage-source noise model and a current-source noise model to simulate EMI noise with the two components of voltage-dependent noise and current-dependent noise in the frequency domain. In order to simulate voltage-dependent EMI noise, we model the power semiconductor that is turning on by a voltage source, whose internal impedance is low. The voltage-source noise is proportional to the amplitude of the voltage. In order to simulate current-dependent EMI noise, we model the power semiconductor that is turning off by a current source, whose internal impedance is large. The current-source noise is proportional to the amplitude of the current. The measured and simulated conducted EMI agreed very well.

This paper presents the mode matching (MM)/finite element method (FEM) hybrid analysis for a short-slot 2-plane coupler, and an optimization process for a wideband design based on a genetic algorithm (GA). The method of the analysis combines a fast modal analysis of the MM which reduces the computation time, with the flexibility of an FEM which can be used with an arbitrary cross-section. In the analysis, the model is reduced into the one-eighth model by using the three-dimensional structural symmetry. The computed results agree well with those by the simulation and the computation time is reduced. The bandwidth is improved by the optimization based on the GA from 2.4% to 6.9% for the 2-plane hybrid coupler and from 5.4% to 7.5% for the 2-plane cross coupler. The measured results confirm the wideband design.

In this paper we report the convergence acceleration effect of the extended node patch preconditioner for the iterative full-wave electromagnetic finite element method with more than ten million degrees of freedom. The preconditioner, which is categorized into the multiplicative Schwarz scheme, effectively works with conventional numerical iterative matrix solving methods on a parallel computer. We examined the convergence properties of the preconditioner combined with the COCG, COCR and GMRES algorithms for the analysis domain encompassed by absorbing boundary conditions (ABC) such as perfectly matched layers (PML). In those analyses the properties of the convergence are investigated numerically by sweeping frequency range and the number of PMLs. Memory-efficient nature of the preconditioner is numerically confirmed through the experiments and upper bounds of the required memory size are theoretically proved. Finally it is demonstrated that this extended node patch preconditioner with GMRES algorithm works well with the problems up to one hundred million degrees of freedom.

This paper describes a numerical assessment methodology of pacemaker EMI triggered by HF-band wireless power transfer system. By using three dimensional full-wave numerical simulation based on finite element method, interference voltage induced at the connector of the pacemaker inside the phantom that is used for in-vitro EMI assessment is obtained. Simulated example includes different exposure scenarios in order to estimate the maximum interference voltage.

A simple, low reflection, and highly-efficient pilot-plant scale microwave irradiation reactor for woody biomass pretreatment was fabricated. Pretreatment is an essential process for effective bioethanol production. The fabricated reactor consists of 8 microwave irradiators which are attached to a metal pipe. The woody biomass mixture which contains water and organic acid flows through the metal pipe and is heated by microwaves at a total power of 12,kW. To design the microwave irradiators, we used a 3D Finite Element Method (FEM) simulator, which was based on the measured complex permittivity data of the woody biomass mixture. The simulation results showed that the reflection coefficient $|S_{11}|$ from the reactor was less than -30,dB when the woody biomass mixture temperature was between 30$^{circ}$C and 90$^{circ}$C. Finally, we experimentally confirmed that the fabricated irradiation reactor yielded a microwave absorption efficiency of 79%.

Recent progress in research on the finite element method (FEM) for optical waveguide design and analysis is reviewed, focusing on the author's works. After briefly reviewing fundamentals of FEM such as a theoretical framework, a conventional nodal element, a newly developed edge element to eliminate nonphysical, spurious solutions, and a perfectly matched layer to avoid undesirable reflections from computational window edges, various FEM techniques for a guided-mode analysis, a beam propagation analysis, and a waveguide discontinuity analysis are described. Some design examples are introduced, including current research activities on multi-core fibers.

Numerical analysis of the photoinductive (PI) field mapping technique for characterizing the eddy-current (EC) probes with tilted coils above a thin metal film was investigated using a two-dimensional transient finite element method (FEM). We apply the FEM model of PI method to observe the influence of metal film materials on the field-mapping images used to characterize EC probes. The effects of film thickness on the PI mapping signal are also shown and discussed. The simulation results using the proposed model showed that the PI signals largely depend on the thermal conductivity and the thickness of the thin metal film. The field-mapping signals using the appropriate actual metal film material for EC probe coil with 0°, 5°, 10°, 15°, and 20° tilt angle are also examined. We demonstrate that the higher resolution in field-mapping images of commercial EC probes can be obtained by given higher thermal conductivity and thinner thickness of metal film. The fundamental understanding of distinct field distribution will aid in the selection of the higher-quality EC probe for accurate inspection with EC testing.

We present a design optimization method of H-plane waveguide components, based on the level set method with the finite element method. In this paper, we propose a new formulation for the improvement of a level set function, which describes shape, location, and connectivity of dielectric in a design region. Employing the optimization procedure, we demonstrate that optimized structures of an H-plane waveguide filter and T-junction are obtained from an initial structure composed of several circular blocks of dielectric.

This paper addresses the on-resistance (Ron) extraction of the DMOS based driver in Power IC designs. The proposed method can extract Ron of a driver from its layout data for the arbitrarily shaped metallization patterns. Such a driver is usually composed of arbitrarily shaped metals, arrayed vias, and DMOS transistors. We use FEM to extract the parasitic resistance of the source/drain metals since its strong contribution to Ron. In order to handle the large design case and accelerate the extraction process, a domain decomposition with virtual terminal insertion method is introduced, which succeeds in extraction for a set of industrial test cases including those the FEM without domain decomposition failed in. For a layout in which the DMOS cells are regularly placed, a sub-domain reuse procedure is also proposed, which obtained a dramatic speedup for the extraction. Even without the sub-domain reuse, our method still shows advantage in runtime and memory usage according to the simulation results.

A persistent current switch (PCS) is used for superconducting applications, such as superconducting magnetic energy storage (SMES) system. The authors have proposed a mechanical switch of Y-Ba-Cu-O (YBCO) bulk as a mechanical PCS. In previous study, the authors have successfully reduced a residual resistance by depositing with metal on contact surface. This paper focused on a current carrying area (called a-spot) on contact surface and presented an effect of deposited metal on electrical contact characteristics in order to clear the contact mechanism. As the results of experiments and simulation using FEM, it became clear that it was effective for reducing the residual resistance from a view point of increasing the a-spot by depositing with metal.

We investigate the usefulness of the topology optimization with the finite element method in the optimization of an H-plane waveguide component. Design sensitivity is computed efficiently using the adjoint variable method. Employing the optimization procedure, optimized structures of an H-plane waveguide filter and T-junction are obtained from an initial homogeneous structure.

The element-by-element finite element method (EBE-FEM) combined with the preconditioned conjugate gradient (PCG) technique is employed in this paper to calculate the coupling capacitances of multi-level high-density three-dimensional interconnects (3DIs). All capacitive coupling 3DIs can be captured, with the effects of all geometric and physical parameters taken into account. It is numerically demonstrated that with this hybrid method in the extraction of capacitances, an effective and accurate convergent solution to the Laplace equation can be obtained, with less memory and CPU time required, as compared to the results obtained by using the commercial FEM software of either MAXWELL 3D or ANSYS.

Vibration characteristic of electromagnetic relay (EMR), including modal and frequency response are important for increasing operational reliability in mechanical environment. The switching contact system, as function execution component of EMR, is the important parts in this product. This paper presents a dynamic model of contact system by introducing Hertz contact theory, and discusses weakly nonlinear oscillation character. Quasilinear simulation analysis using by finite element analyzing software-NASTRAN is investigated. The factors affecting contact vibration characteristic are determined. Finally, theory analysis and simulation results are verified by the vibration test. The model starts from a typical contact system of EMR, but the approach can be applied to other switching electro-mechanical devices.

A method is proposed to investigate the dynamic characteristics of a magnet release in molded case circuit breaker. With the static field assumption, two grids of the magnetic torque and flux linkage are calculated with the variation of the current and air gap, firstly. Considering the influence of tripping torque, coupled with circuit equation and mechanism motion equation, the dynamic characteristics may be obtained with Runge-Kutta 4 method. Experiments have been done to verify the method, and the difference between the calculated results and the experimental results is below 10%. In addition, the influence of the reaction spring on the protection characteristics is analyzed using this method. It demonstrates that the setting current varies with the initial angle and the stiffness of the reaction spring, and the variation with the initial angle of the reaction spring is closely linear but the stiffness nonlinear.

An eddy-current type proximity sensor is a non-contact type sensing device to detect the approach of a conductor by increase of equivalent AC resistance of excitation coil due to eddy current loss in the conductor. In this paper, electromagnetic characteristics of the actual proximity sensor are calculated by FEM and the validity of numerical analysis results are studied. Furthermore, two models that has modified magnetic circuit geometry based on the actual sensor are designed and calculated as numerical experiments. Calculated results are shown as enhanced sensing index or electromagnetic characteristics of the modified sensor. In conclusions, knowledge about the magnetic circuit geometry of the sensor is applied for the enhancement of sensing property.

There have been significant advances in computational electromagnetics (CEM) in the last decade for a variety of antennas and propagation problems. Improvements in single frequency techniques including the finite element method (FEM), the fast mulitipole moment (FMM) method, and the method of moments (MoM) have led to significant simulation capabilities on basic computing platforms. Similar advances have occurred with time domain methods including finite difference time domain (FDTD) methods, time domain integral equation (TDIE) methods, and time domain finite element (TD-FEM) methods. Very complex radiating and scattering structures in the presence of complex materials have been modeled with many of these approaches. Many commercial products have been made available through the efforts of many individuals. The CEM simulators have enabled virtual EM test ranges that have led to dramatic improvements in our understanding of antennas and propagation in complex environments and to the realization of many of their important applications.