计算电磁学在仿真技术中的应用

随着数值计算方法以及计算机技术的进步而迅速发展的计算电磁学,现在正越来越广泛地应用于各种电磁领域。目前以计算电磁学为核心算法的诸多电磁仿真软件的兴起,为微波通信器件的分析和设计提供了有效的工具。本文首先简要介绍了计算电磁学的研究对象;接着提出仿真过程的3步骤——建模、计算、及结果评估;最后重点介绍了几种典型的计算电磁学算法的原理与特点,如有限元法、矩量法、快速多极子算法,以及时域有限差分法,同时,利用以它们为核心算法的仿真软件,分别做相应的仿真算例,并给出了仿真结果得出了一定的结论。     

Modern computer tools for high frequency electromagnetic fields simulation

Modern numerical methods of electromagnetic field simulation are considered and computer codes based on these methods are described. A number of various microwave devices field calculations are presented, estimations of efficiency, accuracy and universality of the codes are given.     

The computational performance of a high-order coupled FEM/BEMprocedure in electropotential problems

This paper presents a thorough analysis of the computational performance of a coupled cubic Hermite boundary element/finite element procedure. This C1 (i.e., value and derivative continous) method has been developed specifically for electropotential problems, and has been previously applied to torso and skull problems. Here, the behavior of this new procedure is quantified by solving a number of dipole in spheres problems. A detailed set of results generated with a wide range of the various input parameters (such as dipole orientation, location, conductivity, and solution method used in each spherical shell [either finite element or boundary elements]) is presented. The new cubic Hermite boundary element procedure shows significantly better accuracy and convergence properties and a significant reduction in CPU time than a traditional boundary element procedure which uses linear or constant elements. Results using the high-order method are also compared with other computational methods which have had quantitative results published for electropotential problems. In all cases, the high-order method offered a significant improvement in computational efficiency by increasing the solution accuracy for the same, or fewer, solution degrees of freedom.     

AWE implementation for electromagnetic FEM analysis

Although full wave electromagnetic systems are large and cumbersome to solve, typically only a few parameters, such as input impedance, S parameters, and far field pattern, are needed by the designer or analyst. A reduced order modelling of these parameters is therefore an important consideration in minimising the CPU requirements. The asymptotic waveform evaluation (AWE) method is one approach to construct a reduced order model of the input impedance or other useful electromagnetic parameters. The authors demonstrate its application and validity when used in conjunction with the finite element method to simulate full wave electromagnetic problems     

电磁计算方法研究进展综述

文章概要介绍了电磁计算方法的研究进展.首先对电磁计算方法的发展进行了概述.其次,对近些年发展出来的若干代表性电磁计算技术,包括快速直接法、非共形区域分解法、高性能并行技术等的发展进行了阐述.再次,对典型电磁计算问题,包括地海复合目标、大规模有限周期结构、电磁逆问题等电磁计算技术的发展进行了简要阐述.最后,对电磁计算方法的发展进行了总结和展望.     

基于有限元方法的波导管结构电磁屏蔽屏蔽效能分析

提出一种在屏蔽箱体孔缝结构的外部增加截止波导管结构的方法,利用截止波导管对高频电磁波的衰减作用来提高屏蔽箱体屏蔽效能。基于有限元法分别对截止波导管的长度、厚度及其形状进行仿真,仿真结果表明:在0.1 GHz~1 GHz频率范围内,随着截止波导管长度及厚度的增加屏蔽箱体屏蔽效能提高15d B以上,圆形和矩形截止波导管对屏蔽效能影响不大。根据实际情况合理选择截止波导管的长度及厚度可以提高微弱信号处理电路的电磁抗干扰能力。     

Calibrating simulation tools for nanometer designs

Next-generation silicon processes will challenge system-on-a-chip (SOC) designers to increase the accuracy of the data they feed to their high level tools. Minimum circuit features of 250 nm (0.25 μm) or below are demanding. The tools that simulate them will need transistor models and interconnect parameters that reflect nothing less than the actual physical properties of the process in which ICs are to be manufactured. These silicon-calibrated models can then pass their accuracy on to capable transistor-level simulation tools. Silicon calibration calls for for tighter relationships and more effective communication than is now found among silicon foundries electronic design automation (EDA) companies, and IC design groups. The EDA tools must be regularly updated, to equip design engineers to cope with the challenges of nanometer design. Although simulation tools may never predict silicon behavior with 100 percent accuracy, EDA tool vendors and IC fabrication facilities share a responsibility to calibrate their tool suites as closely as possible with actual silicon     

Effective method for solving electromagnetic problems

The authors discuss a neural network model for solving electromagnetic problems which can be represented as combinational optimisation problems, with cost functions as the network energy. Solutions correspond to the minimum of energy. An example is given to illustrate the method     

系统矩阵表示的电磁场时域计算方法

为了进一步提高电磁场数值计算效率,把数字信号处理技术和计算电磁学的时域有限差分方法相结合,按照信号与系统理论的概念把求解区域看作一个线性系统,从有源区域的麦克斯韦方程组对称形式出发,推导了离散的时域差分方程组,给出了电磁场求解区域的系统矩阵表达形式.分析了求解差分方程组迭代过程的系统框图,以满足数字信号处理的形式要求.对空域上的微分算子进行矩阵分解,把无条件稳定的电磁场时域离散方程组,通过时间交错迭代格式来处理,给出无条件稳定的方程组的系统矩阵形式,实现电磁波传播过程的模拟.最后,通过一维高斯脉冲的传播、低通滤波器以及紧凑型带阻滤波器的仿真,验证了这种系统矩阵方法的有效性.     

Initial results for automated computational modeling ofpatient-specific electromagnetic hyperthermia

Developments in finite-difference time-domain (FD-TD) computational modeling of Maxwell's equations, super-computer technology, and computed tomography (CT) imagery open the possibility of accurate numerical simulation of electromagnetic (EM) wave interactions with specific, complex, biological tissue structures. One application of this technology is in the area of treatment planning for EM hyperthermia. In this paper, we report the first highly automated CT image segmentation and interpolation scheme applied to model patient-specific EM hyperthermia. This novel system is based on sophisticated tools from the artificial intelligence, computer vision, and computer graphics disciplines. It permits CT-based patient-specific hyperthermia models to be constructed without tedious manual contouring on digitizing pads or CRT screens. The system permits in principle near real-time assistance in hyperthermia treatment planning. We apply this system to interpret actual patient CT data, reconstructing a 3-D model of the human thigh from a collection of 29 serial CT images at 10 mm intervals. Then, using FD-TD, we obtain 2-D and 3-D models of EM hyperthermia of this thigh due to a waveguide applicator. We find that different results are obtained from the 2-D and 3-D models, and conclude that full 3-D tissue models are required for future clinical usage.     

电磁计算十大问题

本专栏文章旨在从雷达、隐身、精确制导、舰船、汽车等几大系统研制角度,提炼出十大电磁计算问题,并略述每个问题的研究进展,以及未来目标,为思考电磁计算未来发展方向抛砖引玉.     

Concurrent network diakoptics for electromagnetic field problems

A new modification to circuit-based diakoptics equations which allows the efficient manipulation of equivalent circuit models which represent Maxwell's equations is presented. A formulation of the diakoptics equations is given whereby torn subnetworks used to form the problem domain under consideration can be connected on a nearest neighbor basis. This formulation allows an algorithm which is suitable for implementation on a parallel computer to be written. It has been implemented on a transputer array configured with two different topologies. The computational efficiency of each topology is appraised and considerable computational advantage demonstrated with respect to the classical sequential variant of the technique. The procedure is then applied to sample electromagnetic field problems in order to verify its utility. Finally it is used to compute the performance of a patch microstrip hybrid coupler     

Piecewise smooth models for electromagnetic inverse problems

This paper presents a new method for constructing one-dimensional (1D) electrical conductivity models of the Earth from surface electromagnetic measurements. The construction of these models is a nonlinear inverse problem that can be approached by linearization techniques combined with iterative methods and Tikhonov's regularization. The standard application of these techniques usually leads to smooth models that represent a continuous variation of conductivity with depth. In this work, the authors describe how these methods can be modified to incorporate what is known in computer vision as the line process (LP) decoupling technique, which has the ability to include discontinuities in the models. This results in piecewise smooth models that are often more adequate for representing stratified media. They have implemented a relaxation technique to construct these types of models and present numerical experiments as well as an application to field data. These examples illustrate the performance of the combined LP and Tikhonov's regularization method     

Topology-finite-element method for solving electromagnetic field problems

The topology-finite-element method has been proposed for solving electromagnetic field problems. This method is characterised by a higher degree of simplicity and standardisation in comparison with the finite-element method. On the other hand, the mathematical model derived by this method is proved to be simple and of evident geometric and physical significance as well, thus creating favourable conditions for making optimal designs in engineering science.     

Three-dimensional finite-element method for solving electromagnetic problems

A 3-dimensional numerical method of determining the vector fields within a closed lossless electromagnetic system is described. The method is used to find the dominant-mode resonant frequencies for two cases of a rectangular cavity partially loaded with dielectric.     

On iterative approaches for electromagnetic rough-surfacescattering problems

Iterative techniques developed for solving general systems of linear equations have been applied to systems resulting from electromagnetic rough-surface scattering problems. Previously used iterative procedures that model the multiple scattering of the electromagnetic energy are shown to be mathematically equivalent to the application of stationary iterative procedures to the system of equations resulting from the standard moment method. Convergence difficulties that are sometimes observed with these approaches are due to the inherent limitations of the stationary techniques. The performances of the stationary approaches are compared with that of several conjugate-direction-based nonstationary iterative procedures through the application to a series of scattering surfaces that yield rapidly changing conditioning of the moment method interaction matrix. The stationary algorithms give the quickest convergence when applied to the systems with the best conditioning, but the nonstationary techniques prove much more robust in other more ill-conditioned situations     

Time domain electromagnetic simulation for microwave CADapplications

Recent progress in time domain modeling is highlighted. Basic properties of time-domain simulators are reviewed, and techniques for improving computational efficiency are examined. The use of numerical synthesis through time reversal is discussed. The user interface is briefly considered and typical simulation results are given     

Macro-elements for efficient FEM simulation of small geometricfeatures in waveguide components

This paper introduces a novel class of specially constructed elements aimed at the expedient finite-element modeling of waveguide components containing fine geometric/material features such as dielectric and conducting posts. Instead of utilizing a very fine grid to resolve such fine features, special elements are constructed that capture accurately the electromagnetic properties of the fine features. Since the size of these macro-elements Is commensurate with the size of the elements of the grid used to discretize the volume in which the fine features are embedded, their use results in significant reduction in the number of unknowns in the finite-element approximation of the electromagnetic problem without sacrificing solution accuracy. The numerical implementation and effectiveness of the proposed macro-elements are demonstrated through several numerical experiments     

Preconditioned conjugate gradient methods for solving electromagnetic problems

It is shown that appropriately chosen preconditioners can significantly improve the convergence rate of the conjugate gradient (CG) algorithm as applied to electromagnetic problems. Preconditioners are constructed for the problems of scattering from frequency selective surfaces and scattering from infinite cylinders.