Showing papers on "Computational electromagnetics published in 2010"

Computational Electronics: Semiclassical and Quantum Device Modeling and Simulation

Abstract: Introduction to Computational Electronics Si-Based Nanoelectronics Heterostructure Devices in III-V or II-VI Technology Modeling of Nanoscale Devices The Content of This Book Introductory Concepts Crystal Structure Semiconductors Band Structure Preparation of Semiconductor Materials Effective Mass Density of States Electron Mobility Semiconductor Statistics Semiconductor Devices Semiclassical Transport Theory Approximations for the Distribution Function Boltzmann Transport Equation Relaxation-Time Approximation Rode's Iterative Method Scattering Mechanisms: Brief Description Implementation of the Rode Method for 6H-SiC Mobility Calculation The Drift-Diffusion Equations and Their Numerical Solution Drift-Diffusion Model Derivation Drift-Diffusion Application Example Hydrodynamic Modeling Introduction Extensions of the Drift-Diffusion Model Stratton's Approach Hydrodynamic (Balance, Blotekjaer) Equations Model The Need for Commercial Semiconductor Device Modeling Tools State-of-the-Art Commercial Packages The Advantages and Disadvantages of Hydrodynamic Models: Simulations of Different Generation FD SOI Devices Particle-Based Device Simulation Methods Direct Solution of Boltzmann Transport Equation: Monte Carlo Method Multi-Carrier Effects Device Simulations Coulomb Force Treatment within a Particle-Based Device Simulation Scheme Representative Simulation Results of Multiparticle and Discrete Impurity Effects Modeling Thermal Effects in Nano-Devices Some General Aspects of Heat Conduction Classical Heat Conduction in Solids Form of the Heat Source Term Modeling Heating Effects with Commercial Simulation Packages The ASU Particle-Based Approach to Lattice Heating in Nanoscale Devices Open Problems Quantum Corrections to Semiclassical Approaches One-Dimensional Quantum-Mechanical Space Quantization Quantum Corrections to Drift-Diffusion and Hydrodynamic Simulators The Effective Potential Approach in Conjunction with Particle-Based Simulations Description of Gate Current Models Used in Device Simulations Monte Carlo-k _ p-1D Schrodinger Solver for Modeling Transport in p-Channel Strained SiGe Devices Quantum Transport in Semiconductor Systems Tunneling General Notation Transfer Matrix Approach Landauer Formula and Usuki Method Far-From-Equilibrium Quantum Transport Mixed States and Distribution Function Irreversible Processes and MASTER Equations The Wigner Distribution Function Green's Functions Nonequilibrium Keldysh Green's Functions Low Field Transport in Strained-Si Inversion Layers NEGF in a Quasi-1D Formulation Quantum Transport in 1D-Resonant Tunneling Diodes Coherent High-Field Transport in 2D and 3D Conclusions Appendix A: Electronic Band Structure Calculation Appendix B: Poisson Equation Solvers Appendix C: Computational Electromagnetics Appendix D: Stationary and Time-Dependent Perturbation Theory Each chapter concludes with "Problems" and "References"

Closed-Form Green's Functions in Planar Layered Media for All Ranges and Materials

Abstract: An important extension of the two-level discrete complex image method is proposed to eliminate any concerns on and shortcomings of the approximations of the spatial-domain Green's functions in closed form in planar multilayered media. The proposed approach has been devised to account for the possible wave constituents of a dipole in layered media, such as spherical, cylindrical, and lateral waves, with the aim of obtaining accurate closed-form approximations of Green's functions over all distances from the source. This goal has been achieved by judiciously introducing an additional level into the two-level approach to pick up the contributions of lateral waves in the spatial domain. As a result, three different three-level algorithms have been proposed, investigated, and shown that they work properly over all ranges of distances from the source. In addition to the accuracy of the results at all distances, these approaches also proved to be robust and computationally efficient as compared to the previous algorithms, which can be attributed to the fact that the sampling of the spectral-domain Green's functions in the proposed approaches gives proper emphasis to the associated singularities of the wave types in the spectral domain. However, the judicious choices of the sampling paths may not be enough to get accurate results from the approximations unless the approximating functions in the spectral domain can provide similar wave natures in the spatial domain. To address this issue, the proposed algorithms employ two different approximations; the rational function fitting methods to capture the cylindrical waves (surface waves), and exponential fitting methods to capture both spherical and lateral waves. It is shown and numerically verified that a linear combination of exponential functions in the spectral domain represent the lateral waves at the interface of the involved layers.

Electromagnetic Modeling of Through-Silicon Via (TSV) Interconnections Using Cylindrical Modal Basis Functions

Abstract: This paper proposes an efficient method to model through-silicon via (TSV) interconnections, an essential building block for the realization of silicon-based 3-D systems. The proposed method results in equivalent network parameters that include the combined effect of conductor, insulator, and silicon substrate. Although the modeling method is based on solving Maxwell's equation in integral form, the method uses a small number of global modal basis functions and can be much faster than discretization-based integral-equation methods. Through comparison with 3-D full-wave simulations, this paper validates the accuracy and the efficiency of the proposed modeling method.

Height Retrieval of Isolated Buildings From Single High-Resolution SAR Images

Abstract: Detection of man-made structures in urban areas, in terms of both geometric and electromagnetic features, from a single, possibly high resolution (HR), synthetic aperture radar (SAR) image is a highly interesting open challenge Within this framework, a possible approach for the extraction of some relevant parameters, describing the shape and materials of a generic building, is proposed here The approach is based on sound electromagnetic models for the radar returns of each element of the urban scene A fully analytical representation of electromagnetic returns from the scene constituents to an active microwave sensor is employed Some possible applications of feature extractions from real SAR images, based on the aforementioned approach, have already been presented in the literature as first examples of potentiality of a model-based approach, but here, the overall theory is analyzed and discussed in depth, to move to general considerations about its soundness and applicability, and the efficiency of further applications may be derived For the sake of conciseness, although the proposed approach is general and can be applied for the retrieval of different scene parameters (in principle, anyone contributing to the radar return), we focus here on the extraction of the building height, and we assume that the other parameters are either a priori known (eg, electromagnetic properties of the materials) or have been previously retrieved from the same SAR image (eg, building length and width) An analysis of the sensitiveness of the height retrieval to both model inaccuracies and errors on the knowledge of the other parameters is performed Some simulation examples accompany and validate the solution scheme that we propose

Uncertainty Analyses in the Finite-Difference Time-Domain Method

Abstract: Providing estimates of the uncertainty in results obtained by Computational Electromagnetic (CEM) simulations is essential when determining the acceptability of the results. The Monte Carlo method (MCM) has been previously used to quantify the uncertainty in CEM simulations. Other computationally efficient methods have been investigated more recently, such as the polynomial chaos method (PCM) and the method of moments (MoM). This paper introduces a novel implementation of the PCM and the MoM into the finite-difference time -domain method. The PCM and the MoM are found to be computationally more efficient than the MCM, but can provide poorer estimates of the uncertainty in resonant electromagnetic compatibility data.

An E-J Collocated 3-D FDTD Model of Electromagnetic Wave Propagation in Magnetized Cold Plasma

Abstract: A new three-dimensional finite-difference time-domain (FDTD) numerical model is proposed herein to simulate electromagnetic wave propagation in an anisotropic magnetized cold plasma medium. Plasma effects contributed by electrons, positive, and negative ions are considered in this model. The current density vectors are collocated at the positions of the electric field vectors, and the complete FDTD algorithm consists of three regular updating equations for the magnetic field intensity components, as well as 12 tightly coupled differential equations for updating the electric field components and current densities. This model has the capability to simulate wave behavior in magnetized cold plasma for an applied magnetic field with arbitrary direction and magnitude. We validate the FDTD algorithm by calculating Faraday rotation of a linearly polarized plane wave. Additional numerical examples of electromagnetic wave propagation in plasma are also provided, all of which demonstrate very good agreement with plasma theory.

Time-reversal focusing in microwave hyperthermia for deep-seated tumors

Abstract: A fast beam-forming method for hyperthermia treatment of deep-seated tumors is described and verified. The approach is based on the time-reversal characteristics of Maxwell equations. The basic principle of the method is coupling of the electromagnetic modeling of the system with the actual application. In this modeling the wavefront of the source is propagated through a patient-specific model from a virtual antenna placed in the tumor of the model. The simulated radiated field is then captured using a computer model of the surrounding antenna system. The acquired amplitudes and phases are then used in the real antenna system. The effectiveness of this procedure is demonstrated by calculating the power absorption distribution using FDTD electromagnetic simulations of a realistic 2D breast model as well as a 2D neck model. Several design parameters, i.e. number of antennas, operating frequency and dimensions, have been evaluated by performance indicators. The promising results suggest that the development of this technique is pursued further.

Multiphysics Modeling: Electro-Vibro-Acoustics and Heat Transfer of PWM-Fed Induction Machines

Abstract: The design of variable-speed electrical machines involves several fields of physics, such as electromagnetism, thermics, mechanics, and also acoustics. This paper describes the analytical multiphysics models of a computer-aided-design software which is applied to inverter-fed traction induction machines. The electromagnetic model computes rotor and stator currents, the induction-machine traction characteristics, and the radial air-gap flux density. The mechanical and acoustic models compute the motor's audible magnetic noise level due to Maxwell forces. The thermal model based on 3-D nodal network computes the transient temperature of different parts of the motor. These fast models make it possible to couple the software with some optimization tools. Some simulation results are presented on a self-ventilated closed motor and compared to experiments.

GPU-Accelerated Method of Moments by Example: Monostatic Scattering

Abstract: In this paper, we combine and extend two of our previous works to provide a more complete solution for the GPU acceleration of the Method of Moments, using CUDA by NVIDIA. To this end, the formulations of the original 1982 Rao-Wilton-Glisson paper are revisited, and the scattering analysis of a square PEC plate is considered as a simple example. One of the primary contributions of the paper is to serve as a guide for the implementation of other GPU-accelerated computational electromagnetic routines. As such, this provides a background on general-purpose GPU computation, as well as insight into the finer details of the implementation. The results computed compared well with reference values. From a performance point of view, the GPU implementation was found to be significantly faster. The fastest measured speedup for one of the phases of the Method of Moments computations was more than a factor of 140. This translated into a speedup of about a factor of 45, when the entire Method of Moments solution process for the problem was considered.

Modeling of Nonlaminated Electromagnetic Suspension Systems

Abstract: Eddy currents induced within nonlaminated electromagnetic actuators by time-varying magnetic fields have a strong effect on the dynamics and control of electromagnetic suspension systems. This paper examines the modeling of these suspension systems and resolves two important problems: 1) the effect of time-varying flotor position on electromagnetic force production and 2) the proper manner in which to model voltage-mode operation of the suspension. The models developed are explicit functions of actuator material and geometric properties. The investigation focuses on axisymmetric cylindrical electromagnetic actuators. Similar results are provided for nonlaminated actuators with C-core stators. Experimental results are presented that demonstrate the accuracy of the modeling approach.

On the Solution of 2-D Inverse Scattering Problems via Source-Type Integral Equations

Abstract: With reference to inverse scattering problems, two different integral equation models belonging to the class of source-type integral equations are reviewed, discussed, and properly compared. In particular, starting from the concept of degree of nonlinearity of the scattering problem, universal plots and useful convenience maps are derived and exploited to foresee which is the most convenient integral equation model to adopt for modeling the scattering phenomena at hand. Numerical examples, dealing with both synthetic and experimental data, are reported and discussed. The results fully confirm the theoretical analysis.

Simple Electromagnetic Modeling Procedure: From Near-Field Measurements to Commercial Electromagnetic Simulation Tool

Abstract: As the first part of a study that aims to propose tools to take into account some electromagnetic compatibility aspects, we have developed a model to predict the electric and magnetic fields emitted by a device. This model is based on a set of equivalent sources (electric and magnetic dipoles) obtained from the cartographies of the tangential components of electric and magnetic near fields. One of its features is to be suitable for a commercial electromagnetic simulation tool based on a finite element method. This paper presents the process of modeling and the measurement and calibration procedure to obtain electromagnetic fields necessary for the model; the validation and the integration of the model into a commercial electromagnetic simulator are then performed on a Wilkinson power divider.

A Nonspurious 3-D Vector Discontinuous Galerkin Finite-Element Time-Domain Method

Abstract: We propose a nonspurious vector discontinuous Galerkin finite-element time-domain (DG-FETD) method for 3-D electromagnetic simulation. To facilitate the implementation of numerical fluxes for domain decomposition, we construct the DG-FETD scheme based on the first-order Maxwell's equations with variables E and H. The LT/QN and the CT/LN edge elements are employed to represent E and H, respectively (or vice versa), to suppress spurious modes, and the Riemann solver is utilized as the numerical flux to correct fields on the interfaces between adjacent subdomains. Numerical experiments show the nonspurious property of the proposed method.

Discrete-Time Network and State Equation Methods Applied to Computational Electromagnetics

Abstract: The representation of electromagnetic structures by lumped element circuits is revisited. Net- work models can be established by a subsequent ap- plication of system identification and circuit synthesis methods to data obtained by numerical simulation or from measurement. Network models provide a com- pact description of electromagnetic structures and can contribute significantly to the formulation of electro- magnetic field problems and their efficient solution. On the field level network methods are introduced by seg- mentation of the electromagnetic structures and appli- cation of the field form of Tellegen's theorem. Methods for synthesis of lumped element models for lossless as well as lossy linear reciprocal multiports and for ra- diating structures are discussed. The state equation method as a general framework for lumped element network description is presented. Discrete time repre- sentations on the basis of Richards transformation and wave digital filter formulation are introduced. I. Introduction The design of modern high-speed analog and digital elec- tronics makes use of distributed passive circuit struc- tures. The modeling of distributed circuits requires full- wave electromagnetic analysis. Usually the whole circuitry contains lumped as well as distributed subcircuits con- nected via interconnects or transmission lines such that each interconnect or connecting transmission line carries a single transverse mode only. This allows the segmen- tation of the circuits by cutting through the connecting transmission lines. The circuit segments obtained in this way, exhibiting a number of n open transmission lines each of them carrying a single transverse mode only in the considered frequency band, is called a multiport or n-port, respectively (1). Whereas lumped element multi- ports can be treated by methods of network theory (2) distributed circuits require electromagnetic full-wave mod-

Electromagnetic Scattering by Finite Periodic Arrays Using the Characteristic Basis Function and Adaptive Integral Methods

Abstract: We introduce a novel technique that combines the AIM algorithm with the characteristic basis function method (CBFM) to solve the problem of electromagnetic scattering by large but finite periodic arrays. An important advantage of using the CBFM for this problem is that we only need to analyze a single unit cell to construct the characteristic basis functions (CBFs) for the entire array. The CBFs are generated by illuminating a single unit cell with a plane wave incident from different angles, for both the θ- and φ-polarizations. The initial set of CBFs, generated in the manner described above, are then downselected by applying a singular value decomposition (SVD) procedure and retaining only the left singular vectors whose corresponding singular values fall above a threshold. Next, in the conventional CBFM, we derive a reduced matrix by applying the Galerkin procedure and solve it directly if its size is manageable. However, when solving an array problem, which precludes the direct-solve option, we can utilize the adaptive integral method (AIM) algorithm, detailed below, not only to accelerate the solution but to reduce memory requirements as well. Numerical examples are included in this communication to demonstrate the accuracy and the numerical efficiency of the proposed technique.

Nyström Method Solution of Volume Integral Equations for Electromagnetic Scattering by 3D Penetrable Objects

Abstract: The volume integral equations (VIEs) for electromagnetic (EM) scattering by three-dimensional (3D) penetrable objects are solved by Nystrom method. The VIEs are essential and cannot be replaced by surface integral equations (SIEs) for inhomogeneous problems, but they are usually solved by the method of moments (MoM). The Nystrom method as an alternative for the MoM has shown much promise and has been widely used to solve the SIEs, but it is less frequently applied to the VIEs, especially for 3D EM problems. In this work, we implement the Nystrom method for 3D VIEs by developing an efficient local correction scheme for singular and near singular integrals over tetrahedral elements. The scheme first interpolates the unknown functions within the tetrahedral elements and then derives analytical solutions for the resultant singular or near singular integrals after singularity subtraction. The scheme is simpler and more efficient in implementation compared with those based on the redesign of quadrature rules for the singular or near singular integrands. Numerical examples are presented to demonstrate the effectiveness of the proposed scheme and its convergence feature is also studied.

A Four-Discrete-Position Electromagnetic Actuator: Modeling and Experimentation

Abstract: In this paper, an electromagnetic actuator having four discrete positions is discussed. The principle, the modeling, and an experimental device of this actuator are presented in this study. This actuator is composed of a mobile permanent magnet, four fixed permanent magnets, which ensure the holding of the discrete positions, and two perpendicular wires to switch independently in two perpendicular directions. The mobile part has four discrete positions, two in each direction. An electromagnetic actuator modeling has been realized to compute the magnetic and electromagnetic forces exerted on the mobile magnet and its displacement. The experimental device was designed using this model and then manufactured. The stroke of the mobile part is 1 mm times 1 mm. The driving current ranges from 3 to 7 A. A comparison between experimental and modeled results is carried out. Good agreement on the displacement curves and on the rise times is observed for all the range of controlling currents.

An FFT-Accelerated Time-Domain Multiconductor Transmission Line Simulator

Abstract: A fast time-domain multiconductor transmission line (MTL) simulator for analyzing general MTL networks is presented. The simulator models the networks as homogeneous MTLs that are excited by external fields and driven/terminated/connected by potentially nonlinear lumped circuitry. It hybridizes an MTL solver derived from time-domain integral equations (TDIEs) in unknown wave coefficients for each MTL with a circuit solver rooted in modified nodal analysis equations in unknown node voltages and voltage-source currents for each circuit. These two solvers are rigorously interfaced at MTL and circuit terminals, and the resulting coupled system of equations is solved simultaneously for all MTL and circuit unknowns at each time step. The proposed simulator is amenable to hybridization, is fast Fourier transform (FFT)-accelerated, and is highly accurate: 1) It can easily be hybridized with TDIE-based field solvers (in a fully rigorous mathematical framework) for performing electromagnetic interference and compatibility analysis on electrically large and complex structures loaded with MTL networks; 2) It is accelerated by an FFT algorithm that calculates temporal convolutions of time-domain MTL Green functions in only O(N t log2 N t ) rather than O(N t 2) operations, where N t is the number of time steps of simulation. Moreover, the algorithm, which operates on temporal samples of MTL Green functions, is indifferent to the method used to obtain them; 3) It approximates MTL voltages, currents, and wave coefficients, using high-order temporal basis functions. Various numerical examples, including the crosstalk analysis of a (twisted) unshielded twisted-pair (UTP)-CAT5 cable and the analysis of field coupling into UTP-CAT5 and RG-58 cables located on an airplane, are presented to demonstrate the accuracy, efficiency, and versatility of the proposed simulator.

Improvement of Numerical Stability for the Computation of Transients in Lines and Cables

Abstract: This paper discusses numerical stability problems of a frequency-dependent transmission-line and cable modeling approach used for electromagnetic transient analysis. Time-domain numerical errors due to the discrete computation of convolution integrals can be estimated in terms of transfer function parameters for a given line or cable model. Based on this estimation, a methodology for the improvement of numerical stability is presented. The numerical advantages of the new method are supported by demonstrations and comparisons with existing models. The method presented in this paper is applicable to power cables and transmission lines.

Supercomputer aware approach for the solution of challenging electromagnetic problems

Abstract: |It is a proven fact that The Fast Fourier Transform(FFT) extension of the conventional Fast Multipole Method (FMM)reduces the matrix vector product (MVP) complexity and preservesthe propensity for parallel scaling of the single level FMM. In thispaper, an e–cient parallel strategy of a nested variation of the FMM-FFT algorithm that reduces the memory requirements is presented.The solution provided by this parallel implementation for a challengingproblem with more than 0.5 billion unknowns has constituted the worldrecord in computational electromagnetics (CEM) at the beginning of2009.1. INTRODUCTIONRecent years have seen an increasing efiort in the development of fastand e–cient electromagnetic solutions with a reduced computationalcost regarding the conventional Method of Moments. Among others,the Fast Multipole Method (FMM) [1] and its multilevel version, theMLFMA [2,3] have constituted one of the most important advances inthat context.This development of fast electromagnetic solvers has gone handin hand with the constant advances in computer technology. Dueto this simultaneous growth, overcoming the limits in the scalabilityof the available codes became a priority in order to take advantageof the large amount of computational resources and capabilities thatare available in modern High Performance Computer (HPC) systems.For this reason, works focused on the parallelization improvement ofthe Multilevel Fast Multipole Algorithm (MLFMA) [4{13] have gainedinterest in last years.Besides, the FMM-Fast Fourier Transform (FMM-FFT) deservesbe taken into account as an alternative to beneflt from massivelyparallel distributed computers. This variation of the single-level FMMwas flrst proposed in [14] as an acceleration technique applied to almostplanar surfaces. Later on, a parallelized implementation was applied togeneral three-dimensional geometries [15]. The method uses the FFTto speedup the translation stage resulting in a dramatic reduction ofthe matrix-vector product (MVP) time requirement with respect tothe FMM. Although in general the FMM-FFT is not algorithmically ase–cient as the MLFMA, it has the advantage of preserving the naturalparallel scaling propensity of the single-level FMM in the spectral (

An Auxiliary Differential Equation Method for FDTD Modeling of Wave Propagation in Cole-Cole Dispersive Media

Abstract: A method for modeling time-domain wave propagation in dispersive Cole-Cole media is presented. The Cole-Cole model can describe the frequency dependence of the electromagnetic properties of various biological tissues with great accuracy over a wide frequency range and plays a key role in microwave medical imaging. The main difficulty in the time-domain modeling of Cole-Cole media is the appearance of fractional time derivatives. In the proposed method a Pade approximation is employed resulting in auxiliary differential equations of integer order. A finite-difference time-domain method is developed to solve the differential equations obtained. The comparison of analytical and calculated relative complex permittivity values over wideband frequency domain proves the validity of the method.

A 3-D Microdosimetric Study on Blood Cells: A Permittivity Model of Cell Membrane and Stochastic Electromagnetic Analysis

Abstract: This paper describes a microdosimetric study on erythrocytes in two parts: an assessment of the membrane dielectric model from permittivity measurements of erythrocyte solutions and its uncertainty, and a quasi-static electromagnetic (EM) analysis solving the Laplace equation, both analytically and numerically. To evaluate the role of the estimated uncertainty, a stochastic EM solution has been conducted; our results highlight the fundamental role of the dielectric modeling on the reliability of electric field values in the cell membrane. Numerical data, from 3-D cell models, confirm the dependence of the electric field distribution on the extra-cellular field polarization.

Comprehensive Compact Models for the Circuit Simulation of Multichip Power Modules

Abstract: This paper proposes the model development of a packaged semiconductor power module, for use in a circuit simulation environment. Focusing on railway traction applications, it considers a state-of-the-art 6.5 kV insulated gate bipolar transistor (IGBT) module, taking into account the antiparallel connection of IGBTs and free-wheeling diodes, and including all main electrothermal and electromagnetic effects associated with the multichip structure. The description of semiconductor physics is coupled with self-heating effects; electromagnetic phenomena associated with the packaging, layout, and interconnections are also taken into account. To optimize the compromise between accuracy and computational effort, the device models are based on a mixed physical and behavioral description, and are scalable to be representative of a desired number of parallel devices and to allow for the introduction of parasitic elements, as required. Electromagnetic effects are modeled by means of equivalent lumped elements, extracted by numerical simulation of an accurate 3-D structural assembly model. The description of transient thermal phenomena relies on a finite-difference approach that considers the use of both essentially 1-D lumped equivalent models and fully 3-D distributed description. The model is validated statically and dynamically, against both data-sheet information and measurements; a selection of simulation examples demonstrates its usefulness and versatility. Although developed for a specific application scenario, the proposed approach is of general validity.

Efficient Cohomology Computation for Electromagnetic Modeling

Abstract: The systematic potential design is of high importance in computational electromagnetics. For example, it is well known that when the efficient eddycurrent formulations based on a magnetic scalar potential are employed in problems which involve conductive regions with holes, the so-called thick cuts are needed to make the boundary value problem well defined. Therefore, a considerable effort has been invested over the past twenty-five years to develop fast and general algorithms to compute thick cuts automatically. Nevertheless, none of the approaches proposed in literature meet all the requirements of being automatic, computationally efficient and general. In this paper, an automatic, computationally efficient and provably general algorithm is presented. It is based on a rigorous algorithm to compute a cohomology basis of the insulating region with state-of-art reductions techniques—the acyclic sub-complex technique, among others—expressly designed for cohomology computations over simplicial complexes. Its effectiveness is demonstrated by presenting a number of practical benchmarks. The automatic nature of the proposed approach together with its low computational time enable the routinely use of cohomology computations in computational electromagnetics.

Keeping Time with Maxwell's Equations

Abstract: Introducing a commercial FETD solver breaks new ground in EM field simulation. Based on the DGTD method, it allows unstructured geometry-conforming meshes to be used for the first time in transient EM field simulation. Since the underlying method doesn't require the solution of a large matrix equation, its computer memory usage is modest. Simulation speed is optimized without compromising accuracy or stability by introducing an innovative local timestepping procedure. In this procedure, small time steps are taken only where needed in small mesh elements while appropriately larger time steps are used in larger mesh elements. Furthermore, a local implicit time-stepping algorithm is employed with selected elements to further improve simulation speed. DGTD is a competitive alternative to traditional FDTD-based methods to solving Maxwell's equations in the time domain. The applications presented here include the electromagnetic pulse susceptibility of the differential lines in a laptop computer, the radar signature of a landmine under undulating ground,the TDR of a bent flex circuit, and the return loss of a connector. All of these examples involve complicated/ curved geometries where the flexibility of the unstructured meshes used in DGTD provides powerful advantages over simulation by conventional brickshaped FDTD and FIT meshes.

Implementation of Collocated Surface Impedance Boundary Conditions in FDTD

Abstract: Surface impedance boundary conditions (SIBCs) for finite-difference time-domain (FDTD) are implemented with collocated H and E components in which first-order spatial finite difference have been used for the spatial derivatives Transient error analysis is done for the reflected field for the whole possible range of modeled material conductivity Magnitude and phase error analysis of the calculated reflection coefficients for wideband pulses is presented as well The resulting numerical errors are compared with the errors of traditional SIBCs implementation when the tangential magnetic fields on the boundary are approximated with the neighboring FDTD magnetic field component located at half-cell size distance in space and half time step behind in time It is shown that the collocated fields approach is considerably more accurate for both constant real resistive and dispersive complex lossy dielectric SIBCs, in both magnitude and especially phase Unlike the traditional approach, it is stable for all values of modeled material conductivity The collocated fields approach is also applied to SIBCs with coating, and the transient and reflection coefficient errors are studied It is shown that in contrast to the traditional implementation, it is stable for arbitrarily thin coating and for any substrate conductivity, and requires storage only half of the auxiliary coefficients when computing the convolution integrals

Direct Drive Permanent Magnet Wind Generator Design and Electromagnetic Field Finite Element Analysis

Abstract: The wind generator's simulation model is set up to study the electromagnetic field by finite element method. Based on Maxwell electromagnetic theory, the distribution of magnetic field is obtained and generator characteristics are calculated in the case of no load and load transient operation. The post processing helps to optimize the design of the generator. Meanwhile, some practical project problems are solved.