FEM analysis of unbounded electromagnetic scattering by the Robiniteration procedure

A new accurate procedure for the FEM solution of unbounded electromagnetic scattering problems is described. The scatterers are enclosed in a fictitious boundary on which a Robin condition is initially guessed, and then iteratively improved using the Green formula. The method does not present interior resonances and is easy to implement     

High-quality computational tools for linear-algebra problems in FEM electromagnetic simulation

A key ingredient of finite-element analysis programs is the linear-algebra solver, typically either a linear-system solver or an eigensolver. The first part of This work tries to justify why it is important to have recourse to publicly available software for addressing this part of the computation. A number of libraries are mentioned as successful examples that exhibit a series of desirable qualities. Although some of these libraries force the programmer to somewhat change the programming style and may be difficult to learn, the benefits usually pay off the extra effort. The second part of the paper describes one of these libraries in some detail, namely SLEPc, the Scalable Library for Eigenvalue Problem Computations, which is used to illustrate the benefits of modem software paradigms for scientific and engineering computing.     

Nonlinear macromodeling with AWE

Asymptotic Waveform Evaluation (AWE) [1, 2] is an efficient and general technique for simulating linear(ized) circuits. This paper discusses strategies for macromodeling nonlinear circuits with AWE. One approach, multi-region AWE macromodels, represents an extension of piecewise linear models, with the addition of internal states. Each region represents an AWE approximation to a linearization (at some bias point) of the nonlinear circuit of interest. In addition a technique is presented for initializing the internal states when the model transitions from one linearization to another during a transient simulation. The second approach is to treat nonlinearity as a second order effect that is superimposed on a linear solution as a post-processing step. A relaxation algorithm that exploits the reuseable AWE solution is employed to modify the linear solution so that it accounts for the macromodel nonlinearity.This work was supported by the Semiconductor Research Corporation.     

Multipoint Galerkin asymptotic waveform evaluation for model orderreduction of frequency domain FEM electromagnetic radiationproblems

In this paper, a model order reduction technique is presented. This technique, known as Galerkin asymptotic waveform evaluation (GAWE), or multipoint Galerkin asymptotic waveform evaluation (MGAWE) if multiple expansion points are considered simultaneously, can be used to reduce matrices describing electromagnetic (EM) phenomena generated through the finite element method (FEM) to a smaller space while still accurately approximating the characteristics of the original responses. The resulting solution procedure of using GAWE or MGAWE, to solve FEM equations allows for wideband frequency simulations with a reduction in total computation time. Numerical simulations using these methods are shown along with traditional methods such as using an LU decomposition at each frequency point of interest and asymptotic waveform evaluation (AWE). Comparisons in accuracy as well as computation time are also given     

Fast RCS pattern fill using AWE technique

An extrapolation technique is adapted to predict the monostatic radar cross-section (RCS) pattern from a few pattern value calculations. This asymptotic waveform evaluation (AWE) approach eliminates a need to resolve the system when an iterative solver is employed. A three-dimensional application is considered to demonstrate the accuracy of the technique     

A hybrid FEM/MOM technique for electromagnetic scattering andradiation from dielectric objects with attached wires

A hybrid formulation is presented, which combines the method of moments (MOM) with the edge-based vector finite element method (FEM) to solve electromagnetic radiation problems from structures consisting of an inhomogeneous dielectric body of arbitrary shape attached to one or more perfectly conducting bodies. While either method alone fails to model these structures efficiently, a combination of both finite element and moment methods provides an excellent way to solve these problems. The FEM is employed to handle the interior domain of inhomogeneous dielectric bodies and the method of moments is used to develop surface integrals that relate the field quantities on boundary surfaces with the equivalent surface currents. These integral equations are then coupled to the finite element equations through the continuity of the tangential magnetic fields across the hybrid boundaries     

电磁场数据可视化系统设计与实现

探讨了电磁场数据可视化的表现形式,相应系统显示的数据内容、流程、总体设计与各模块功能设计,研究了随机分形地形生成,等值线算法,结合计算机图形学,实现等值线图,彩色云图,传播路径图显示。     

GPU-accelerated fem solver for three dimensional electromagnetic analysis

A new Graphics Processing Unit (GPU) parallelization strategy is proposed to accelerate sparse finite element computation for three dimensional electromagnetic analysis. The parallelization strategy is employed based on a new compression format called sliced ELL Four (sliced ELL-F). The sliced ELL-F format-based parallelization strategy is designed for hastening many addition, dot product, and Sparse Matrix Vector Product (SMVP) operations in the Conjugate Gradient Norm (CGN) calculation of finite element equations. The new implementation of SMVP on GPUs is evaluated. The proposed strategy executed on a GPU can efficiently solve sparse finite element equations, especially when the equations are huge sparse (size of most rows in a coefficient matrix is less than 8). Numerical results show the sliced ELL-F format-based parallelization strategy can reach significant speedups compared to Compressed Sparse Row (CSR) format.     

介质体电磁散射的偶极子模型法研究

提出用偶极子模型法来分析介质体的电磁散射.该方法以矩量法和Schaubert-Wilton-Glisson(SWG)基函数为基础,把介质体剖分成一定数量的四面体元.在介质体内,把含有公共面的体元对等效成电偶极子;在介质体表面,把边界面及其对应的体元等效成电偶极子.当等效偶板子单元离观察点大于临界距离时,用偶极子模型法计算阻抗矩阵元素.偶极子模型法简单易操作,不仅能大幅度降低阻抗矩阵的计算时间,还简化了边界条件的处理.数值结果表明了该方法的高效性及与原方法几乎相同的计算精度.     

Design and experimental implementation of an electromagnetic engine valve drive

In conventional internal combustion engines, engine valve displacements are fixed relative to crankshaft position. If these valves were actuated as a variable function of crankshaft angle, significant improvements in fuel economy could be achieved. To this end, a new type of electromagnetic valve drive system (EMVD) for internal combustion engines was more recently proposed. This EMVD incorporates a disk cam with a very desirable nonlinear profile which that functions as a nonlinear mechanical transformer. Modeling and simulation results showed significant advantages of this EMVD over previously designed electromagnetic engine valve drives. In this articles, we describe an experimental implementation of the proposed EMVD, which was developed to confirm these benefits. The EMVD apparatus was designed, constructed, and integrated into a computer-controlled experimental test stand. The experimental results confirm the benefits of using a nonlinear mechanical transformer in a motordriven engine-valve spring system, as seen in the small average power consumption and low valve seating velocity. In addition, a valve transition time sufficient for 6000-rpm engine operation was achieved. The results also suggest ways to improve the EMVD apparatus in the future.     

调幅射频电磁场人体辐照实验系统的设计与实现

设计可用于调幅射频电磁场生物效应研究的人体辐照平台,分别从硬件系统部分和软件系统部分两方面进行介绍。硬件系统由射频信号发生模块、功率放大模块、阻抗匹配模块以及发射天线构成,其接收到由软件系统发出的载波、调制频率、调制深度以及功率参数指令后,进而实时产生相应的调幅射频电磁场。实际测量结果表明,设计的调幅射频电磁场人体辐照实验系统具有良好的性能参数,该系统为人体调幅射频电磁场生物效应研究提供一个使用方便、参数可控的电磁辐照平台。     

基于复杂电磁辐射环境的电磁辐射检测方法研究与分析

随着信息技术的不断发展,多种电磁辐射源同时存在的电磁辐射环境日益复杂,各类场所的人为电磁能量显著增加。为了实现对复杂电磁辐射环境的分析,预防或减少电磁辐射的伤害,通过对单一辐射源检测方法开展研究,创新性地提出了复杂电磁辐射环境的概念及检测方法,包括相对中心检测法和相对轴线检测法,并结合单一辐射源检测结果,对现代城市环境中常见的复杂电磁辐射环境开展了检测,最后对电磁辐射情况进行总结并提出建议。     

CAVERN: a prediction code for cavity electromagnetic analysis

The authors describe an application of the fast Fourier Bessel transform to speed up their jet-engine scattering-analysis code, CAVERN. Because of the engine termination, it is typically necessary to break up the computational domain into that of the inlet and engine regions. In the inlet region, the fields are modeled using ray techniques, whereas the complex engine must be modeled using a different and more-rigorous formulation. A need then arises for interfacing the two computational domains, in a manner that maintains field continuity. Since the engine is always housed in a cylindrical or near-cylindrical inlet section, one way for interfacing the two computational regions is to represent the ray and engine fields using a cylindrical-modal expansion. The engine can then be characterized, via the modal-scattering matrix, in a manner independent of the excitation. Ray fields can be readily turned into modes, and vice versa, and continuity of the fields at the interface of the two regions is maintained, since both use the same modal representation. However, for inlets whose diameter spans 50λ or so, the task of transforming rays into modes and vice versa can become a bottleneck, because of the large number of propagating modes present in the cavity. Use of the fast Fourier Bessel transform can alleviate this difficulty, as described     

A model for discretization error in electromagnetic analysis ofcapacitors

The error due to discretization in a method-of-moments analysis of a parallel plate or metal-insulator-metal (MIM) capacitor is discussed. A technique related to Richardson extrapolation is used to develop a model for the error due to subsectional discretization. The results are for Galerkin's method using rooftop basis functions; however, the technique can be applied to any variational moment-method calculation. An expression is presented for the error in capacitance calculations, which is shown to hold for changes in geometry and dielectric constant. In addition, the expression for error is shown to be accurate for a wide range of meshing geometries. Surprisingly, the error model is not an upper bound, but rather is met nearly in equality for all geometries considered. Thus, the error may be simply subtracted from the calculated value for a more accurate result     

Analysis of the electromagnetic scattering by thick gratings usinga combined FEM/MM solution

The problem of diffraction by a thick, conducting grating situated in an inhomogeneous dielectric slab is investigated using the generalized network formulation. This formulation combines the method of moments and the finite-element method, permitting the treatment of periodic elements of arbitrary cross section and inhomogeneous profiles. Solutions are presented for both transverse electric (TE) and transverse magnetic (TM) polarizations. Transmission gratings composed of rectangular conductors filled with dielectric materials of arbitrary profiles are studied     

电磁感应车双车追踪设计与实现

本设计通过对小车设计制作整体思路、机械调教、电路设计、算法设计、调试等方面的介绍,详尽地阐述了整个设计过程的思想和创意。具体表现在机械的合理规划、电路的创新设计、算法方面的独特想法。     

血管病变激光疗法的有限元模拟分析

利用Matlab下的有限元算法求解生物组织热传输Pennes方程,模拟静脉血管的组织环境,得到810nm GaAlAs半导体激光作用下,静脉血管的温度响应.以此为平台,预测静脉曲张激光疗法的疗效,同时在此指导下开展动物实验.     

对某舰载机柜电磁屏蔽效能的分析

介绍了某舰载机柜电磁屏蔽要求和结构形式,详细论述了机柜电磁屏蔽效能的理论分析、仿真计算和实物测试,对计算和测试结果进行了分析。     

雷达仿真系统中电磁干扰环境的仿真设计和实施

雷达仿真系统是为检测雷达设备的抗干扰能力以及在各种电磁环境下的工作性能而设计的,包括有源干扰和无源干扰的模拟仿真。本文阐述了无源干扰即杂波的散射模型和仿真过程;从同步脉冲干扰的基本原理出发,阐明在雷达工作环境仿真系统中距离拖引、速度拖引、虚假目标等同步脉冲有源干扰的设计和实施过程;并针对工作在搜索和跟踪交替模式下的相控阵雷达提出自适应综合干扰方式;最后分析并总结了系统仿真时为真实、有效地模拟电磁干扰环境应注意的关键问题。     

Non-uniform wavelets in electromagnetic scattering analysis

Non-uniform wavelets are constructed to benefit from both adaptively refined grids for modelling edge singularities and compression of moment matrices with wavelet bases. They are applied to the analysis of electromagnetic scattering problems