Finite element modeling and multigrid preconditioner using adaptive triangular meshes

The letter describes a finite element method (FEM) using adaptive triangular meshes for the modeling of microwave devices. A robust preconditioning technique is provided for the fast solution of the resultant FEM matrix equations. The proposed preconditioner is based on a multigrid scheme for the vector-scalar potential FE formulation of the electromagnetic problem. Numerical experiments demonstrate its superior numerical convergence.     

Hierarchical multilevel potential preconditioner for fast finite-element analysis of microwave devices

A robust hierarchical multilevel preconditioning technique is presented for the fast finite-element analysis of microwave devices. The proposed preconditioner is based on a hierarchical multilevel scheme for the vector-scalar potential finite-element formulation of electromagnetic problems. Numerical experiments from the application of the new preconditioner to the finite-element analysis of microwave devices are used to demonstrate its superior numerical convergence and efficient memory usage.     

Hybrid multilevel/multigrid potential preconditioner for fast finite element modeling

A robust hybrid multilevel/multigrid potential preconditioner is introduced for the fast and robust finite-element modeling of electromagnetic structures. The proposed preconditioning process combines the advantages of the hierarchical multilevel preconditioner and the nested multigrid potential preconditioner into a novel preconditioner with superior computational versatility. Numerical experiments from the application of the new preconditioner to the finite-element analysis of microwave devices demonstrate its superior numerical convergence and efficient memory usage.     

一种基于高阶矢量基函数的叠层预条件技术

基于六面体的高阶叠层基函数,提出了一种新颖的构造预条件矩阵的方法.该方法基于叠层基函数特有的嵌套性质,利用特殊的编号策略,将由有限元方法导致的系数矩阵分成块矩阵的形式,最后由不完全LU分解(ILU)导出近似的预条件矩阵.结合该预条件技术,发展了一种叠层预条件-GMRES算法,并将该预条件算法用于加速三维腔体散射的矢量有限元/边界积分(FE-BI)矩阵方程的迭代求解,讨论了该预条件算法中块矩阵ILU分解截断门限T_dr对算法的影响.     

Simulation of thermal diffusion in transistors using transmissionline matrix modelling

A variety of solid-state devices are being developed for use in systems where they are required to produce pulses of microwave power at specified duty cycles. The design of these devices is interesting as they will be smaller and have less thermal capacity than an equivalent continuous-wave source generating the same microwave power. This size reduction is important as it can result in improved electrical efficiency and a higher frequency of operation. The author describes the application of transmission line matrix diffusion modelling to the transient thermal design of a transistor structure and compares the technique with finite difference and finite element approaches     

微波组件用pin梁式引线管热元模型分析研究

在微波组件中,有源器件是主要热源,它们对微波组件的热性能具有决定性的作用。基于ANSYS有限元分析软件,采用有限元分析法,针对某型号微波组件用pin梁式引线管热元模型进行了模拟和分析。模拟结果与实际样品的红外热像测试结果基本一致,表明热元模型正确地反映了pin管在组件中的热性能状况情况。热元模型的建立能快速、简便地获得缉件中单个管芯的温度分布情况,可缩短热设计与测试周期。     

A highly effective preconditioner for solving the finite element-boundary integral matrix equation of 3-D scattering

A highly effective preconditioner is presented for solving the system of equations obtained from the application of the hybrid finite element-boundary integral (FE-BI) method to three-dimensional (3-D) electromagnetic scattering problems. Different from widely used algebraic preconditioners, the proposed one is based on a physical approximation and is constructed from the finite element method (FEM) using an absorbing boundary condition (ABC) on the truncation boundary. It is shown that the large eigenvalues of the finite element (FE)-ABC system are similar to those of the FE-BI system. Hence, the preconditioned system has a spectrum distribution clustered around 1 in the complex plane. Consequently, when a Krylov subspace based method is employed to solve the preconditioned system, the convergence can be greatly accelerated. Numerical results show that the proposed preconditioner can improve the convergence of an iterative solution by approximately two orders of magnitude for large problems.     

An Efficient MAINV Preconditioned COCG Method for FEM Analysis of Millimeter Wave Filters

The modified AINV (MAINV) sparse approximate inverse preconditioner is applied to the conjugate orthogonal conjugate gradient (COCG) iterative method for solving a large systems of linear equations resulting from the use of edge finite element method (FEM). The proposed preconditioner is derived from basic AINV process by adding pivots compensation strategy to avoid the potential breakdowns. Numerical experiments on several typical millimeter wave structrues demonstrate the effectiveness of the MAINV-COCG method, in comparison with other conventional methods.     

有限元法应用于微波和光波器件的问题和发展

本文就有限元法应用于微波和光波器件的原理、问题和最新进展作了综合评述。文中讨论了适用于不同问题的变分公式的意义；着重讨论了避免和消除虚模的方法和处理开放边界的技术；还对代表该领域发展趋势的三个方面，即边棱元法。非线性结构及有限元程序的前后处理问题进行了评论和展望。     

一种基于神经网络的微波器件快速建模方法北大核心CSCD

随着微波器件结构复杂度的增长和产品性能要求的提高,微波器件建模不仅要能够描述其理想电磁特性,还要能快速准确反映多物理参数对器件性能的影响。虽然神经网络已经被引入到微波器件领域,但是将其应用于器件的多物理特性建模的研究还比较少。文章提出了一种基于人工神经网络的多物理参数建模方法来表示输入输出变量之间的非线性关系。提出了一种高效的神经网络多物理参数模型,并针对该模型引入了一种新的训练算法。所提出的模型可以快速准确地预测微波器件的多物理响应,如滤波器的S参数特性曲线、离子敏感场效应晶体管的输出特性曲线等。与有限元方法相比,此方法可以节省约98%的计算成本与99%的计算时间,为实现快速高效的微波器件行为级建模提供一种可行方法。     

改进的稀疏近似逆预条件算法求解电磁场边值问题

提出了一种MAINV稀疏近似逆预条件算法,用于改善电磁场边值问题的有限元分析所产生的的线性系统的迭代求解。该预条件子是在基本AINV算法基础上,在分解过程中对可能导致算法崩溃的极小主元进行实时补偿,从而获得高质量的预条件子。数值结果表明,MAINV预条件子对SQMR以及若干经典迭代法的加速效果十分明显;此外,与其他常规预条件子相比较,MAINV具有更好的求解性能。     

求解Helmholtz方程的新型稀疏近似逆预条件算法

提出了一种新型预条件算法,用于对有限元法离散Helmholtz方程所产生的大型稀疏复对称且高度不定的线性系统进行高效迭代求解。该新型预条件子是在复拉普拉斯偏移算子的基础上结合改进的稀疏近似逆算法来得到。通过改善矢量有限元线性系统自身的谱特性,该预条件算法既可避免迭代中的不稳定情况,同时也能较大提高迭代求解效率。数值结果表明,与若干常用预条件算法相比,所提出的预条件算法更加有效。     

E面分支波导耦合器的二维有限元法分析

基于二维有限元的分析途径 ,本文提出了四端口E面分支波导耦合器的一种分析方法。利用该方法 ,开发了相应的分析软件 ,并已成功应用于“微波模块设计制造一体化系统”中。一个四端口 4 .9dB五分支波导耦合器实例的计算结果与实验结果以及HFSS(一种基于三维有限元的高频结构仿真软件 )仿真结果的比较 ,证明该分析途径及软件实现是精确而有效的 ,并可广泛应用于同类微波器件的分析。     

求解波导问题FEM线性系统的RIC预条件算法

提出了一种新型RIC预条件COCG迭代技术,用于改善有限元法仿真分析光电工程问题所产生的高度非正定的线性系统的迭代求解.提出的RIC预条件子是针对基本IC算法可能出现的分解崩溃问题,通过对主元进行加强来获得稳定的分解过程,进而产生高效的预条件子.数值试验表明,提出的RIC预条件子不仅能有效避免COCG迭代等方性崩溃,而且比常用的预条件子更高效;此外,RIC对其他若干Krylov子空间迭代法求解性能的改善作用也相当明显.     

“邻居单元”为基础的预条件方法及其应用

该文提出了一种具有物理意义的预条件方法--"邻居单元"为基础的预条件方法。该方法充分考虑了矩阵元素中的"主要"信息量,可以有效加快迭代收敛速度。在构造预条件因子时,采用从目标的"几何结构剖分"出发,而不是从"矩阵元素"出发确定"基权函数之间的作用量关系",这样保证了构造预条件矩阵的计算复杂度仅为O(N)。作为实例,该文将这种预条件方法与共轭梯度方法结合应用于矩量法基站天线分析所得方程的求解,数值结果表明了该文方法的有效性。     

高功率微波效应的多物理场建模方法研究

为了实现对微波器件高功率微波效应的分析,主要从不同尺度半导体器件和波导器件出发,基于具有谱精度的谱元时域法,开展从微米尺度到纳米尺度半导体器件电热耦合一体化分析的方法以及高功率微波气体放电效应及抑制机理的研究.得到了半导体器件在电磁信号作用下发生的电热参数分布变化规律和微波器件在高功率微波下发生的气体放电及其抑制机理,根据以上相关效应机理,可为复杂电磁环境中的器件设计提供理论指导.     

A polymer electro-optic modulator with ultra wide-band and low driving voltage

In this paper, a polymer electro-optic modulator is designed and simulated using the full vectorial finite element method. First order edge elements are used in finite element implementation, and the finite element technique is used to obtain modulator response thoroughly. From the numerical analysis, frequency dispersions of modulator’s important parameters, such as microwave effective index nm , microwave characteristic impedance ZC and microwave loss a, are extracted. Our design exhibits elec...     

一种堆叠式3D IC的最小边界热分析方法

目前的热分析工具仅仅支持单芯片的热分析,而堆叠式的三维芯片(3D IC)在同一封装中包含多个堆叠的芯片,对芯片的散热和温度管理提出了更高的要求,并且在热分析过程中需要处理复杂的边界条件.本文提出的最小边界法可以准确且有效地处理堆叠式3D IC的边界条件,简化了三维芯片封装的热模型;同时,本文提出在堆叠式3D IC的稳态热量分析中通过将连接点分类、采用预处理矩阵的方法加速整个全局热传导矩阵的求解过程,从而简化热分析流程.实验结果表明:将有限元方法作为基本的热分析方法,用最小边界法处理堆叠式3D IC,可以准确分析芯片的热分布;同时通过高效的预处理矩阵可以减少共轭梯度法求解中90%的迭代次数.     

一种基于不连续伽辽金方法求解多区域目标散射问题的优化预处理器

在电磁散射问题中,由均匀介质和金属组合而成的多区域结构目标在天线仿真、雷达成像等工程问题中有着广泛应用.针对多区域目标的散射问题,研究了不连续伽辽金（discontinuous Galerkin, GD）方法在多区域面积分（surface integral equation, SIE）矩量法中的使用,同时提出了一种优化的距离稀疏预处理（optimized distance sparse preconditioner, O-DSP）方法.该方法根据阻抗矩阵中不同积分算子随距离变化的特性来个性化选择预处理矩阵,进一步增加了预处理矩阵的稀疏性.数值计算表明,相比之前的距离稀疏预处理方法,优化的预处理矩阵非零元素仅为以前的一半,而且具有相同加速迭代效果.     

Microwave Amplifiers Employing Integrated Tunnel-Diode Devices

A series of shunt-tuned integrated microwave tunnel-diode devices utilizing unencapsulated beam lead tunnel diodes and including tuning and stabilizing circuitry have been fabricated using tantalum thin-film technology for use as the active element in microwave reflection amplifiers. The theoretical properties of such devices have been explored, and data relating to their design and measured performance are presented in detail. Finally, the successful use of these devices as the active elements in a series of absolutely stable circulator-coupled reflection amplifiers at 4 and 6 GHz has been demonstrated.