A new well-conditioned Integral formulation for Maxwell equations in three dimensions

We present a new boundary integral equation dedicated to the solution of the boundary problem of a perfectly electrically conducting surface for the harmonic Maxwell equations in unbounded domains. Any solution of the harmonic Maxwell equations is represented as the electromagnetic field generated by a combination of electric and magnetic potentials. These potentials are those appearing in the classical combined field integral equation (CFIE), but their coupling is realized by an operator Y/spl tilde//sup +/ instead of a coefficient. Therefore, the integral equation obtained can be viewed as a generalization of the CFIE. In this paper, we propose an explicit construction of the coupling operator Y/spl tilde//sup +/ which is designed to approximate the exterior admittance operator of the scattering obstacle. A local approximation by the admittance operator of the tangential plane seems to be relevant thanks to the localization effects related to high-frequency phenomena. The provided numerical simulations show that this formulation leads to linear systems that are better conditioned compared to more classical integral equations, which speeds up the resolution when solved with iterative techniques.     

Modified equations of coupled surface acoustic waves

Modified equations for coupled surface acoustic waves (SAWs) are derived on the basis of the complex Umov-Poynting theorem and the Green’s function of a piezoelectric half-space. The equations can be used to calculate the frequency characteristics of various SAW devices. Relationships for frequency-dependent parameters of the equations describing SAW excitation are derived. The efficiency of the computation of frequency characteristics of devices that is based on the obtained relationships is demonstrated by the calculation for a ladder SAW-resonator 64°YX-LiNbO₃ filter. The results of computations and measurements are in good agreement.     

A surface integral formulation of Maxwell equations for topologically complex conducting domains

A general and effective method is presented to numerically solve the electric field integral equation (EFIE) for topologically complex conducting domains by the finite element method. A new technique is proposed to decompose the surface current density into a solenoidal part and a nonsolenoidal remainder to avoid the low frequency breakdown. The surface current density field is approximated through div-conforming (facet) elements. The solenoidal part is represented through the space of the discrete approximation D of the surface divergence operator in the subspace spanned by the facet elements, whereas the nonsolenoidal remainder is represented through its complement. The basis functions of the space and its complement are evaluated, respectively, by the and pseudo-inverse of the matrix D. The completeness of the -pinv basis functions is studied. Unlike the loop-star and loop-tree basis functions, the -pinv basis functions allow to deal with topologically complex conducting domains in a general and readily applicable way. A topological interpretation of the "-pinv" decomposition is given and a general and simple method to evaluate the and pseudo-inverse of D is proposed. The computational complexity of the proposed method is discussed.     

A hybrid computational electromagnetics formulation for Simulation of antennas coupled to lossy and dielectric volumes

A heterogeneous hybrid computational electromagnetics method is presented, which enables different parts of an antenna simulation problem to be treated by different methods, thus enabling the most appropriate method to be used for each part. The method uses a standard frequency-domain moment-method program and a finite-difference time-domain program to compute the fields in two regions. The two regions are interfaced by surfaces on which effective sources are defined by application of the Equivalence Principle. An extension to this permits conduction currents to cross the boundary between the different computational domains. Several validation cases are examined and the results compared with available data. The method is particularly suitable for simulation of the behavior of an antenna that is partially buried, or closely coupled with lossy dielectric volumes such as soil, building structures or the human body.     

Integral equations and discretizations for waveguide apertures

We present integral equations and their discretizations for calculating the fields radiated from arbitrarily shaped antennas fed by cylindrical waveguides of arbitrary cross sections. We give results for scalar fields in two dimensions with Dirichlet and Neumann boundary conditions and for (vector) electric and magnetic fields in three dimensions. The discretized forms of the equations are cast in identical format for all four cases. Feed modes can be TM, TE, or transverse electromagnetic (TEM). A method for numerically computing the modes of an arbitrarily shaped, cylindrical waveguide aperture is also given     

Generalized mobility law for drain current modeling in Si MOStransistors from liquid helium to room temperatures

A generalized mobility law for drain current modeling in Si MOSFETs operated in the linear region which is valid between room and liquid helium temperatures, is presented. It is based on the existence of a power-law parameter that is a unique value of n for each temperature and that allows the linearization of an appropriate function of gate voltage at sufficiently strong inversion, depending on the drain current and the transconductance of the device. It is demonstrated that a unique value of n can be found for each temperature with a very high precision. This model has been successfully applied to a number of n- and p-channel MOS transistors, and can be used to obtain an accurate extraction of the main device parameters and, therefore, a precise modeling of the transfer characteristics in the whole range of temperature for strong inversion operation     

Integral equations with reduced unknowns for the simulation oftwo-dimensional composite structures

A set of integral equations with reduced unknowns is derived for modeling two-dimensional inhomogeneous composite scatterers. The scatterer is first simulated in terms of thin curvilinear material layers of constant thickness. The traditional integral equations corresponding to each inhomogeneous layer are then manipulated in a manner allowing the identification of a new equivalent current component to replace two of the traditional ones across the layer. The given integral equations require approximately 2N current-component unknowns for their numerical implementation instead of the 3N unknowns generally required with traditional formulations. The implied computational efficiency though, was obtained at the expense of some complexity in the resulting pair of integral equations. To test the validity of the derived integral equations, special attention is given to a moment-method implementation of the authors' compact set of integral equations, with emphasis on the analytical evaluation of the diagonal and near-diagonal elements of the impedance matrix. Scattering patterns are presented as computed with the compact set of integral equations. These are further compared with measured data and computations using alternate analytical techniques. In all cases, these were in excellent agreement with corresponding results achieved by alternate methods     

Generalized expressions for characterizing a linear multiportcircuit coupled with external fields

The outputs of a linear multiport circuit immersed in external fields are analyzed using the S-parameters in frequency and time domains. It is suggested that the matched output voltage is a proper and convenient parameter for characterizing the circuit coupled with external fields, since it can be measured easily in a higher frequency range than a few hundred megahertz. The output voltages of the circuit terminated with loads of arbitrary impedance are calculated from measured values of the matched output voltages, the S-parameters of the circuit, and the reflection coefficients of the loads. Related formulas are derived for the characterization     

Integral equation formulation for inhomogeneous anisotropic mediaGreen's dyad with application to microstrip transmission linepropagation and leakage

A straightforward numerical technique based on the equivalence principle is presented to determine the complete spectral Green's dyad for inhomogeneous anisotropic media. This method is relevant to guided-wave problems where propagation characteristics are desired in the axial transform domain. Spectral Green's components are determined from a one-dimensional polarization-type integral equation. This method is very simple and versatile, and can be used to model continuously varying or stratified dielectric media with permittivity dyads of the most general form. As an application, a microstrip transmission line residing on a generally orientated uniaxial and biaxial substrate is considered, and new results for higher-order mode leakage are presented     

Generalized Impedance Boundary Condition for Conductor Modeling in Surface Integral Equation

A generalized impedance boundary condition is developed to rigorously model on-chip interconnects in the full-wave surface integral equation by a two-region formulation. It is a combination of the electric-field integral equation for the exterior region and the magnetic-field integral equation for the interior conductive region. The skin effect is, therefore, well captured. A novel integration technique is proposed to evaluate the Green's function integrals in the conductive medium. Towards tackling large-scale problems, the mixed-form fast multipole algorithm and the multifrontal method are incorporated. A new scheme of the loop-tree decomposition is also used to alleviate the low-frequency breakdown for the formulation. Numerical examples show the accuracy and reduced computation cost.     

广义预测自校正控制隐式算法及其仿真研究

大量的工业生产过程都具有非线性、时滞性、不确定性和时变的特点,要建立精确的模型十分困难,因此研制具有鲁棒性的自校正器逐渐引起人们的关注。介绍了一种广义预测自校正控制隐式算法且对其进行仿真研究,分析仿真结果,总结参数变化对整个系统性能的影响,结果说明了该算法的有效性。     

A Generalized Surface Integral Equation Formulation for Analysis of Complex Electromagnetic Systems

A novel method is presented to analyze the electromagnetic characteristics of systems consisting of a large number of scatterers with different shapes and materials. In the method, nearly located scatterers are grouped together, while large bulk materials are divided into subblocks with adequate sizes. A scatterer group or a subblock forms a basic block of the system, and each block is contained with a virtual reference surface. A generalized transition matrix defined on the reference surface is used to characterize the electromagnetic characteristics of the block. The generalized transition matrix relates the rotated tangential components of the scattered fields or the equivalence sources to the rotated tangential components of the incident fields directly. The generalized transition matrix can be calculated for each block independently using proper methods according to its structure and material. Surface integral equations are established on all the virtual reference surfaces, which can be solved by moment method to get the electromagnetic characteristics of the whole system. Characteristic basis functions and synthetic basis functions can be applied to further reduce the unknown number, while fast multipole method can be used to accelerate the evaluation of interactions. Two-dimensional examples are provided to verify the method.     

A coupled mode formulation by reciprocity and a variational principle

A coupled mode formulation for parallel dielectric waveguides is presented via two methods: a reciprocity theorem and a variational principle. In the first method, a generalized reciprocity relation for two sets of field solutions(E^{(1)}, H^{(1)})and(E^{(2)}, H^{(2)})satisfying Maxwell's equation and the boundary conditions in two different mediaepsilon^{(1)}(x,y)andepsilon^{(2)}(x,y), respectively, is derived. Based on the generalized reciprocity theorem, we then formulate the coupled mode equations. The second method using a variational principle is also presented for a general waveguide system which can be lossy. The results of the variational principle can also be shown to be identical to those from the reciprocity theorem. The exact relations governing the "conventional" and the new coupling coefficients are derived. It is shown analytically that our formulation satisfies the reciprocity theorem and power conservation exactly, while the conventional theory violates the power conservation and reciprocity theorem by as much as 55 percent and the Hardy-Streifer theory by 0.033 percent, for example.     

Generalized linear-parabolic law: a mathematical model for thermaloxidation of silicon

Silicon dioxide growth curves under a variety of oxidation conditions are analyzed. The results indicated that the growth curve is not the linear-parabolic equation as predicted by the Deal-Grove model. Instead, a generalized form of the linear-parabolic equation in which the coefficients are allowed to accommodate the change in the sign and thickness dependency is desirable to describe the silicon oxidation process. It is also shown that the thickness dependence of the rate constant with appropriate approximations can be expressed explicitly in a functional form     

单相电压型PWM整流电路原理分析与仿真

详细分析单相电压型PWM整流电路的工作原理和工作模式,说明通过对PWM电路进行控制,选择合适的工作模式和工作时序,可使PWM整流电路的输出直流电压得到有效的稳定.同时也调节了交流侧电流的大小和相位,实现能量在交流侧和直流侧的双向流动,并使变流装置获得良好的功率因数.最后建立其Matlab的仿真模型,验证了设计的正确性.     

An exact formulation for the vector potential of a cylindricalantenna with uniformly distributed current and arbitrary radius

An exact formulation is given for the vector potential and corresponding electric fields associated with a uniform current cylindrical dipole antenna of arbitrary radius. The exact expressions converge rapidly in the induction and near-field regions of the antenna. They are completely general and independent of the usual restrictions involving the wavelength, field point distance, dipole radius and length. The properties of these expressions allow them to be readily used for the efficient as well as accurate computational modeling of cylindrical wire antennas. An exact expression for the cylindrical wire kernel which is analytically as well as numerically convenient to work with is presented. It is demonstrated that the integral of the kernel can be expressed in terms of a series which involves a generalized exponential integral and higher-order associated integrals. Several methods for evaluating the generalized exponential integral are discussed, including some useful asymptotic expansions. A numerically stable forward recurrence relation for the higher-order associated integrals is also presented     

Obtaining the equations of motion for parametrically coupled oscillators or waves

When the equations of motion for any parametric system are written in terms of an appropriate set of normal modes, these equations have a general coupled-mode form which depends on the number of frequency components present and on the order of nonlinearity considered, but not on any other details of the specific system considered. This paper presents a simple procedure, based on a Hamiltonian approach, for obtaining the most general set of parametric coupled-mode equations for any number of frequency components and any order of nonlinearity. The procedure applies to parametrically coupled normal modes which grow in time, or to parametrically coupled waves which grow in distance and/or in time. The general equations obtained in this way are useful for pedagogic purposes and for general discussions of parametric interactions; for checking or even for bypassing detailed derivations on specific physical systems; and for proving the Manley-Rowe relations, which emerge very directly from the resulting general equations.     

n沟6H-SiC MOSFET阈值电压的温度特性模拟与分析

分析了n沟6H—SiCMOSFET的杂质不完全离化和SiO2—SiC界面存在大量界面陷阱等问题，研究了影响6H—SiCMOSFET器件阅值电压温度特性的诸因素。通过解析式计算和MEDICI软件模拟，得到了多种因素共同作用下的器件闪值电压的温度特性。研究表明，体内杂质的不完全离化、表面空间电荷层中的杂质离化程度和特定分布的界面电荷，对阅值电压的温度特性有显著的影响。