Efficient Analysis of Millimeter Wave Circuit Using Numerical Calibration Technique

In this paper, A numerical technique, called short-open calibration (SOC), in conjunction with edge-based finite element method (FEM) is employed to analyze millimeter wave circuit that can be segmented into two distinct section: static model of feedlines and dynamic model of circuit discontinuity. The derivation of reflection coefficient of 3D discontinuities is arranged in two steps. In the first step, this SOC technique is incorporated into the FEM for mesh truncation of computaional domain. In this way, much faster convergence is achieved for large-sparse linear matrix equations from FEM by this termination than by perfectly matching layers (PML). The field distribution of the dominated mode in uniform feedlines and entire circuit is obtained individually by exciting a pair of even and odd impressed voltages along the struture. In step two, Scattering parameters based on the voltages and current defintion is calculated by integral of electric and magnetic fields. Numerical solutions for a class of planar circuit discontuities are very well compared with those published in the available literatures.     

Analysis of Complex Dielectric Phase Gratings by Hybrid FEM-Gaussian Mode Expansion Technique

Hybrid technique of finite element method (FEM) and Gaussian mode expansion method is implemented for the analysis of transmission property of dielectric phase gratings used in holographic power combining systems. It takes advantages of the versatility of FEM and the simplicity of the mode expansion method. Apparently, this hybrid method is well suited for the analysis of phase gratings with complex profiles, which provide more degrees of structural freedom than those of classical rectangular groove gratings. The transmitted fields of an array of two and three fundamental Gaussian beams through the multi-stepped and curved gratings are calculated by the hybrid method. Numerical results show that much less phase distortion can be fulfilled for the reconstructed pseudo-plane wave by the modified phase gratings, especially the curved ones. This is advantageous for improving the combining efficiency in spatial millimeter wave and sub-millimeter wave power combining systems.     

Hybrid finite element-modal analysis of jet engine inlet scattering

With the goal of characterizing jet engine inlets, a hybrid finite element-modal formulation is presented for the analysis of cavities with complex terminations. The finite element method (FEM) is used to find the generalized scattering matrix for an N-port representation of the complex termination. Where N is the number of traveling modes in the cavity. The cavity is assumed to be circular at the termination (engine) but the remainder of the cavity can be of arbitrary cross section. The scattered fields are obtained by tracing the fields back out of the cavity via a high frequency or modal technique with the generalized scattering matrix used in determining the fields at an aperture near the irregular cavity termination. “Proof of concept” results are presented and several issues relating to the implementation of the FEM are addressed. Among these, a new artificial absorber is developed for terminating the FEM mesh and the suitability of edge or node based elements is examined     

Hybrid analysis of reflector antennas including higher order interactions and blockage effects

The analysis of a reflector antenna system consisting of a feeder, a sub-reflector, and a main-reflector in microwave frequency bands, where the electrical dimensions of the antenna become prohibitively large for the use of a rigorous numerical method, has been performed by high-frequency asymptotic techniques (HFATs). As a result, the radiation patterns and input impedances of the antenna system were calculated based on an approximation: the radiation characteristics of the feed, sub-reflector and main-reflector are independent from each other. In this study, as an effort to alleviate the inaccuracy due to the exclusion of higher order mutual interactions existing among those subsystems, three different hybrid methods [finite-element method/method of moment (FEM/MOM) + physical optics (PO), FEM/MOM + geometrical theory of diffraction (GTD), and FEM/MOM + PO + physical theory of diffraction (PTD)] are introduced in the context of an iterative algorithm. The interactions between the feed and sub-reflector are accounted by a hybrid method which combines the FEM with the MOM; FEM/MOM. Whereas, the interactions between the objects in the FEM/MOM domain and the main-reflector are taken into account through the iteration: the fields and currents in the FEM/MOM domain are updated using the fields and currents obtained from the HFAT domain and vise-versa. These three methods are applied to two-dimensional reflector configurations, and corresponding results are compared in terms of accuracy and efficiency. The accuracy of the hybrid methods, especially those of FEM/MOM + GTD and FEM/MOM + PO + PTD, is found to be comparable to that of a rigorous numerical method. Furthermore, their computational costs are almost independent to the size of the main-reflector and to the distance from the feed point to the main-reflector.     

Electric fields in bone marrow substructures at power-line frequencies

Bone marrow is known to be responsible for leukemia. In order to study the hypothesis relating power-line frequencies electromagnetic fields and childhood leukemia from a subcellular perspective, two models of bone marrow substructures exposed to electric field are computed numerically. A set of cancellous bone data obtained from computed tomography scan is computed using both the finite element method (FEM) and scalar potential finite difference method. A maximum electric field enhancement of 50% is observed. Another model of bone marrow stroma cells is implemented only in FEM using thin film approximation. The transmembrane potential (TMP) change across the gap junctions is found to range from several to over 200 microV. The two results suggest that imperceptible contact currents can produce biologically significant TMP change at least in a limited number of bone marrow stroma cells.     

Surface integral equation method for the analysis of an obliquelystratified half-space

The radiation of a source in the presence of an obliquely stratified half-space is studied using the surface integral equation method. A generalized extinction theorem for the obliquely stratified half-space problem is derived, which gives eight surface integral equations for the fields. The Green's functions for the stratified media are found by a semianalytical method. These surface integral equations can be used to solve the rather complicated two-dimensional problem by the one-dimensional finite element method (FEM), which saves computer memory and computation time compared to the conventional two-dimensional FEM. for some special cases, the results obtained by this method are compared with those obtained by the numerical mode matching method and the Fourier integral technique. Excellent agreement has been observed between them. This method is general for any obliquely stratified half-space with arbitrarily many layers in each region     

改进的IPO与FEM混合法分析复杂电大腔体电磁散射

对传统的迭代物理光学法(IPO)进行了改进,使之适合于分析具有非完纯导电边界的电磁问题,并与矢量有限元方法(FEM)相结合,对内壁涂敷介质的具有复杂终端结构的电大尺寸腔体的电磁散射特性进行分析.通过Fresnel反射系数,利用IPO方法处理腔体内壁比较平滑的介质涂敷区域,在结构复杂的终端区域,利用FEM进行分析.利用交界面上场强连续条件实现两个区域之间的电磁耦合.通过迭代,计算出腔体内部稳定的电磁场分布,进而获得整个腔体的散射特性.由于在介质涂敷附近区域避免了FEM处理过程,从而可以节省大量计算时间和内存消耗.     

Radiation characteristics of cavity backed aperture antennas infinite ground plane using the hybrid FEM/MoM technique and geometricaltheory of diffraction

A technique using the hybrid finite element method (FEM)/method of moments (MoM) and geometrical theory of diffraction (GTD) is presented to analyze the radiation characteristics of cavity fed aperture antennas in a finite ground plane. The cavity which excites the aperture is assumed to be fed by a cylindrical transmission line. The electromagnetic (EM) fields inside the cavity are obtained using finite element method (FEM). The EM fields and their normal derivatives required for FEM solution are obtained using: (1) the modal expansion in the feed region and (2) the MoM for the radiating aperture region (assuming an infinite ground plane). The finiteness of the ground plane is taken into account using GTD. The input admittance of open-ended circular, rectangular, and coaxial line radiating into free space through an infinite ground plane are computed and compared with earlier published results. Radiation characteristics of a coaxial cavity-fed circular aperture in a finite rectangular ground plane are verified with experimental results     

Biological cells with gap junctions in low-frequency electricfields

Biological effects have been observed from weak, low-frequency magnetic fields. It has been suggested that the observed effects are due to the induced currents and electric fields. The behavior of cells exposed to an electric field is investigated in this paper. The induced transmembrane potential (TMP) is examined in geometrically complex models of various cell configurations. The TMP is evaluated using the finite element method (FEM), a numerical technique that is well suited to complicated geometries. Because displacement currents can be neglected at very low frequencies, a FEM solver that considers only material conductivity is used. Therefore, our results apply only well below the relaxation frequency. Chains and clusters of gap-connected cells of various sizes are modeled. The conductivity and size of the gap junctions in the cell configurations are also varied. The results for small configurations are compared to models of ellipsoidal cells with shapes similar to those of the configurations. FEM estimates of TMPs in long, cylindrical cell chains are compared to the predictions of the leaky cable model. The FEM approach confirms that gap-junction-connected cells can be treated as a single similarly shaped cell. Gaps influence the potential in the interior of cell configurations, and these effects increase with gap size and conductivity. For configurations to which approximations such as the leaky cable model do not apply, the FEM approach can be used to estimate the TMP, if the model is adapted to fit within computational memory limits     

Higher Order Hybrid FEM-MoM Technique for Analysis of Antennas and Scatterers

A novel higher order large-domain hybrid computational electromagnetic technique based on the finite element method (FEM) and method of moments (MoM) is proposed for three-dimensional analysis of antennas and scatterers in the frequency domain. The geometry of the structure is modeled using generalized curved parametric hexahedral and quadrilateral elements of arbitrary geometrical orders. The fields and currents on elements are modeled using curl- and divergence-conforming hierarchical polynomial vector basis functions of arbitrary approximation orders, and the Galerkin method is used for testing. The elements can be as large as about two wavelengths in each dimension. As multiple MoM objects are possible in a global exterior region, the MoM part provides much greater modeling versatility and potential for applications, especially in antenna problems, than just as a boundary-integral closure to the FEM part. The examples demonstrate excellent accuracy, convergence, efficiency, and versatility of the new FEM-MoM technique, and very effective large-domain meshes that consist of a very small number of large flat and curved FEM and MoM elements, with $p$-refined field and current distributions of high approximation orders. The reduction in the number of unknowns is by two orders of magnitude when compared to available data for low-order FEM-MoM modeling.      

Two-dimensional singular vector elements for finite-elementanalysis

The finite-element method (FEM) exhibits a reduced convergence rate when used for the analysis of geometries containing sharp edges where the electromagnetic field is singular. The convergence of the method can be-improved by introducing singular elements that model analytically predicted singular behavior. A number of authors have developed singular elements that are compatible with the scalar FEM. In this paper, we propose a new singular element that is compatible with edge-based vector finite elements and can cope with any order of singularity while preserving the sparsity of the FEM equations. Edge-based singular elements more correctly model singular fields and thus require fewer unknowns, while avoiding the introduction of spurious modes in the numerical solution. Numerical results verify that the convergence of the FEM is significantly improved     

Parameters Extraction of Millimeter Wave Circuits by Hybrid Vector Finite Element and Moment Method Combined with SOC Technique

This paper presents a hybrid method, which couples the vector finite element method (FEM) and method of moment (MOM) for analyzing the field and current distribution of the millimeter wave circuits. The FEM is applied to handle the interior region of dielectric bodies and MOM is used to solve surface integral equations. Then, These integral expressions are coupled into the FEM equations through the continuity of the tangential fields across the connection boundaries. Simultaneously, the short-open calibration (SOC) technique is used for predicting accurately the scattering parameters of the circuits. Numerical results are well compared with those published in the previous literatures.     

宽带结构吸波材料特性研究

随着科技的发展以及隐身技术在军事上的重要应用,吸波材料在民用和军用领域受到全世界的关注,而结构 型吸波材料以自身的优点成为其中的研究热点。设计了一种两层阻抗性、低电导率的相互正交的Hilbert curve 宽带 结构型吸波材料,采用有限元算法分析其吸波特性。这种结构易于实现,且能在较宽的频带范围内（3GHz-18GHz）提 供良好的吸波性能。     

一种分析准周期结构散射问题的有限元区域分解算法

采用区域分解法和矢量有限元法相结合分析准周期性结构的散射问题.将整个计算区域分成若干个非重叠的子区域,各子域形成自己的有限元线性系统;在子域交界面上引入罗宾传输条件来保证相邻子域的场连续性;通过高斯消去法把求解各子域内部未知量的问题转化为求解交界面上未知量的问题,从而降低计算复杂度.对于一些准周期性结构,利用子结构的几何重复性,能够让电大尺寸问题的求解更加快捷.给出的数值算例证明了该方法的正确性和有效性.     

Scattering analysis of a large body with deep cavities

A numerical scheme is presented for simulating electromagnetic scattering from a large and arbitrarily shaped body, coated with inhomogeneous composite materials, with large and deep cavities. This numerical scheme employs the higher order vector finite-element method (FEM) to discretize the fields inside the cavities and coatings and the higher order boundary integral (BI) method to terminate the FEM computational domain. A highly efficient special solver is designed to eliminate the unknowns inside the cavities, which yields a computed relation (CR) matrix over the cavity's aperture between the tangential electric and magnetic fields. This CR matrix is then combined with the finite element-boundary integral (FE-BI) matrix equation to form a complete linear system for the discrete fields everywhere in the computational domain. The resulting system is solved iteratively using a novel preconditioner derived by replacing the BI with a corresponding absorbing boundary condition (ABC).     

高压JTE终端边界元电场分析

在半导体高压终端研究中，重要的工作之一是终端电场电位分析。国内外以往报道的JTE分析结果除采用解析方法外，数值方法主要采用差分或有限元法。作者利用边界元数值技术，采用“边界元临界电场分析法”，用自主开发的统一的边界元终端分析软件，从新的角度，以单区、双区JTE为例，详细讨论了新的边界元分析法，研究了极值电场分布等情况，得到了物理概念清晰，描述较准确而又简明直观的优化结果。边界元算法独特，优点显著。现有程序不但可用于JTE终端优化分析设计，还可直接用于场板、JTE加场板等终端结构场分析。     

Finite element analysis of MMIC structures and electronic packagesusing absorbing boundary conditions

In this paper, a three-dimensional finite element method (FEM) is employed in conjunction with first and second-order absorbing boundary conditions (ABC's) to analyze waveguide discontinuities and to derive their scattering parameters. While the application of FEM for the analysis of MMIC structures is not new, to the best of the knowledge of the authors the technique for mesh truncation for microstrip lines using the first and higher-order ABC's, described in this paper, has not been reported elsewhere. The scattering parameters of a microstrip discontinuity are computed in two steps. As a first step, the field distribution of the fundamental mode in a uniform microstrip is obtained by exciting the uniform line with the quasi-static transverse electric field, letting it propagate, and then extracting the dominant mode pattern after the higher order modes have decayed. In step two, the discontinuity problem is solved by exciting the structure by using the fundamental mode obtained in step one. The scattering parameters based on the voltage definition are calculated by using the line integral of electric fields underneath the strip. Numerical solutions for several waveguide discontinuities and electronic packages are obtained and compared with the published data     

A spectral Lanczos decomposition method for solving 3-Dlow-frequency electromagnetic diffusion by the finite-elementmethod

A very efficient three-dimensional (3-D) solver for the diffusion of the electromagnetic fields in an inhomogeneous medium is described. The proposed method employs either the node-based or the edge-based finite-element method (FEM) to discretize Maxwell's equations. The resultant matrix equation is solved by the spectral Lanczos decomposition method (SLDM), which is based on the Krylov subspace (Lanczos) approximation of the solution in the frequency domain. By analyzing some practical geophysical problems, it is shown that the SLDM is extremely fast and, furthermore, the electromagnetic fields at many frequencies can be evaluated by performing the SLDM iteration only at the lowest frequency     

Modeling of an Electromechanical Engine Valve Actuator Based on a Hybrid Analytical--FEM Approach

The use of an electromechanical valve actuator (EMVA) formed by two magnets and two balanced springs is a promising tool to implement innovative engine management strategies. This actuator needs to be properly controlled to reduce impact velocities during engine valve operations, but the use of a position sensor for each valve is not possible for cost reasons. It is therefore essential to find sensorless solutions based on increasingly predictive models of such a mechatronic actuator. To address this task, in this paper, we present an in-depth lumped parameter model of an EMVA based on a hybrid analytical--finite-element method (FEM) approach. The idea is to develop a model of EMVA embedding the well-known predictive behavior of FEM models. All FEM data are then fitted to a smooth curve that renders unknown magnetic quantities in analytical form. In this regard, we select a single-wise function that is able to describe global magnetic quantities as the flux linkage and force both for linear and saturation working regions of the materials. The model intrinsically describes all mutual effects between two magnets. The goodness of the dynamic behavior of the model is finally tested on a series of transient FEM simulations of the actuator in different working conditions.      

复合材料飞机上静电放电特性研究

针对碳纤维复合材料(介质)飞机上的静电放电(ESD)展开研究,首先给出复合材料飞机上静电放电的产生原理,并根据飞机上放电电流脉冲波形,建立数值模型,模拟静电荷在复合材料飞机上的积累以及静电荷在飞机上静电放电产生的辐射电场,最后结合有限元方法,计算出复合材料飞机的电容并估算静电放电的能量。与传统的金属飞机不同,这里强调对于静电放电产生的辐射电场,以及静电放电对机载天线的影响均在复合材料飞机环境下计算。