复杂非均匀介质中多偶极层激励的位场分析

本文利用半解析－半数值混合地复杂非均匀介质中单个和多个偶极层所激励的位场进行高效数值求解，并与有限元法结果及实验数据进行了对比验证，获得了满意的一致。该方法已被用于自然电位响应问题的精细建模与求解。     

单轴各向异性分层介质的二维空域格林函数

通过采用２－Ｄ全波离散镜像技术得到了单轴各向异性分层介质结构的空域Ｇｒｅｅｎ函数的解析形式。重点了应用了全小离散镜像技术到２－Ｄ问题中的难点。通过比较,揭示了２－Ｄ问题中极点抽取的必要性。对于近谱变化剧烈的单轴各向异性介质的谱域Ｇｒｅｅｎ函数,采用了矩阵束方法进行拟合。最终结果与数据积分的结果吻合很好。     

各向异性板中激光激发Lamb波的数值模拟

基于谱有限元法和模态展开法,针对各向异性薄板,建立激光激发Lamb波的数值模型,得到各向异性薄板中Lamb波沿不同方向传播的色散曲线及Lamb波的传播特性。数值模拟结果表明,谱有限元法能快速有效地计算各向异性板中导波的相速度、群速度,结合模态展开法能够得到任何方向激光激发的Lamb波;Lamb波沿不同方向传播的速度及色散特性与材料的各向异性性质相关。数值模拟为更好地理解复杂介质中导波的传播、指导激励信号的选择及识别检测信号的模态提供了理论依据。     

基于矢量有限元法的谐振腔通用模拟器设计

开发了基于矢量有限元法的谐振腔通用计算模拟器。该模拟器包括前处理、有限元求解和后处理三部分。首先在前处理中进行三维实体建模和网格剖分,然后采用有限元方法生成矩阵并求解该矩阵,在后处理中计算谐振腔的任意本征频率,Q值及电磁场分布。通过分别对几种不同介质包括各向异性介质加载下的谐振腔进行仿真求解,并将计算结果与商业电磁仿真软件HFSS进行对比,验证了模拟器的可行性以及仿真谐振腔的通用性。     

含电磁双各向异性介质衬底的FSS特性分析

运用谱域Galerkin法对含电磁双各向异性介质衬底的频率选择表面(FSS)进行了分析,概述了算法的基本实现过程,直接以Maxwell方程为基础,逐步推导出该周期结构中的谱域格林函数.文中在衬底介质参数的变动下,对一系列FSS反射系数进行了有效计算,计算结果表明了介质衬底的电磁各向异性特性对FSS频率选择特性的影响.     

FDTD应用于各向异性介质及半空间散射问题

介绍FDTD方法应用于各向异性介质散射分析及其并行计算.基于并矢表面阻抗给出金属表面各向异性介质涂层的等效介质参数公式.讨论铁氧体基片偏置磁场对微带天线辐射方向图的影响,模拟研究了板状各向异性材料介质参数的反演途径.将半空间FDTD应用于金属平板上孔缝散射计算和光学材料表面微缺陷散射近场和散射振幅分析,以及介质光栅Floquet模和传输功率的计算.     

双各向异性Meta材料矩形波导中的导波模分析

将开口谐振环(SRR)作为加载单元,分析了含有Meta材料矩形波导的新型传输特性.由于SRR所引起的双各向异性效应,横电波将出现传播常数随频率增高而减小的异常TEm0模式以及单模传输频带范围增大的TE0n 模式.特别地,当Meta材料成为单轴双各向异性介质时,横电波和横磁波在此新型介质波导中的相速度能够减慢,甚至达到零速度传播.     

双各向异性色散介质电磁波传播Z-时域有限差分分析

基于一种改进的Z变换-时域有限差分(Z-Finite-Difference Time-Domain,Z-FDTD)方法,即将双各向异性色散介质的频域本构方程先转化到Z域中,再利用Z变换的性质将其转换到时域,得到离散时域的FDTD迭代式,分析了双各向异性色散介质电磁波传播特性.由于Omega媒质是一种典型的双各向异性色散介质,以此为例编程计算了垂直入射在Omega介质板情形下产生的同极化和交叉极化电磁波的反射和透射情况,并通过算例和解析解对比验证了算法的正确性,最后对其电磁散射特性进行了分析.     

各向异性衬底上的高温超导(HTS)微带天线

分析了各向异性衬底上的高温超导微带天线特性.选取两种典型的高温超导各向异性介质--GaNdAlO3和SrLaAlO4作为高温超导微带天线的衬底,采用各向异性媒质中的谱域矩量法,对微带天线的输入阻抗和辐射效率进行了计算.计算和分析结果表明,高温超导衬底的各向异性特性会影响高温超导微带天线的性能,而且这种影响因衬底而异,同时,衬底特性随温度的变化也将影响天线的性能.     

屏蔽类带状耦合微带线准静态特性分析的一个新方法

本文利用傅氏级数展开结合样条函数插值和变分技术对屏蔽类带状耦合微带线(两层介质厚度不同)的准TEM模特性进行了分析。首先,使用博氏级数将问题用公式表示,然后应用样条插值和变分技术获得实际解。它与有限元法十分相似,但它具有不必进行单元剖分,矩阵方程阶数低,解答精度高等优点。数值计算结果与文献值吻合很好。该方法还可推广应用于多层介质(n>2)填充的屏蔽耦合微带线的准TEM模特性分析,同时也可考虑导带厚度的效应。     

A partial variational analysis of planar dielectric antennas

The reflection and radiation characteristics of a planar dielectric antenna with arbitrary geometrical configuration are analyzed numerically. A variational equation is first established based on the partial variational principle (PVP), and then solved by the finite element method coupled with the frontal solution technique. The radiation and boundary conditions are incorporated by combining the modal expansion method and the Green's function approach for exterior field representation. The reflection coefficients, the radiation patterns, and the directive and power gains of several antennas with linearized structures are studied and compared     

非Yee网格的FDTD法分析复杂媒质PBG结构的带阻特性

采用电、磁场各分量均位于网格中心的高阶时域有限差分法计算PBG结构的色散特性。对简单媒质问题的计算结果与采用Yee网格时域有限差分法所得一致，但更适合于分析含复杂媒质的问题。计算了三类磁各向异性PBG结构的色散特性曲线，指出：磁各向异性媒质都可明显增宽第一阻带；对称型磁各向异性还增多色散特性曲线中的阻带数，但旋磁型各向异性则不影响阻带数。     

Variational reaction formulation of scattering problem for anisotropic dielectric cylinders

The variational reaction theory is applied to obtain the (E_{Z}, H_{z})formulation for the scattering problem when a plane wave is obliquely incident upon an inhomogeneous and anisotropic dielectric cylinder. The variational equation is then solved by the finite element method together with the frontal solution technique. Numerical results for scattering cross sections of anisotropic LiNbO³cylinders are included to discuss the influence due to material anisotropy and oblique incidence. Also depicted is the guiding characteristics of the cylinder when the inhomogeneous wave is considered, in addition, the formulas of scattering cross sections at low frequencies are derived and compared with the numerical results.     

Hybrid numerical method for harmonic 3-D Maxwell equations:scattering by a mixed conducting and inhomogeneous anisotropicdielectric medium

This article deals with a hybrid numerical method for solving harmonic Maxwell equations in the classical electrodynamic context. This formulation can be used with any body of arbitrary three-dimensional geometry, of perfectly conducting material or dielectric, with locally inhomogeneous and anisotropic behavior laws, and with or without dielectric losses. The mathematical formulation is presented along with applications validating it. The exterior problem is treated by the integral equation method while local equations are used for the dielectric parts of the body. A global variational formulation of the coupled problem is developed for use in discretization by the finite element method. Boundary finite elements are used for integral operators connected with the exterior problem. Localized finite elements are used for the interior problem. Difficulties of irregular frequencies, also called resonant frequencies in the perfectly conducting case, arising from the integral formulation are analyzed in detail and an efficient solution is developed     

各向异性媒质中光子带隙结构色散特性的时域伪谱法分析

本文采用时域伪谱(PSTD)法分析复杂媒质中的光子带隙(PBG)结构,建立了电磁波色散特性的统一数学模型,经数值计算绘出色散曲线.在各向同性媒质情况下所得的曲线,与时域有限差分法及平面波展开法的结果相一致.在各向异性媒质情况下,能展宽原各向同性媒质PBG结构的第一阻带、并增多阻带条数.     

Variational principles compete with numerical iterative methods for analyzing distributed electromagnetic structures

An explicit variational principle (Evp) for the propagation constant of em waves is compared with four numerical tools: the Newton-Raphson algorithm solving a transcendental equation, the spectral domain approach (Sda) applied to the Galerkin method, the 3-D simulatorHfss fromHp, and the finite element method (Fem). Each tool analyses a different planar topology: a lossy dielectric slab supporting surface waves, a planar slotline modelled by transmission line parameters (Tlp), a multilayered high-loss co-planar waveguide, and a shielded microstrip line. For these various structures, the evp is more efficient than previous tools yielding the propagation constant; its explicit form and variational nature yield a drastic reduction of the number of iterations.     

Transversely anisotropic curved optical fibers: variationalanalysis of a nonstandard eigenproblem

A novel variational functional is introduced for the analysis of curved open and closed waveguides. The theory is based on the variational principle for nonstandard eigenvalue problems. The present method is valid for the arbitrary waveguide cross section and arbitrary radius of curvature for closed waveguides; for open guides, the radius should be sufficiently large, because the method predicts the real part of the propagation constant, not the imaginary part, which gives the attenuation in curved open structures. The dielectric medium can be homogeneous or nonhomogeneous with transverse and/or longitudinal anisotropy. As an example of the method, curved isotropic and anisotropic single-mode fibers with two different kinds of anisotropy models are studied. The analysis includes field distributions, changes in the dispersion curves due to reformed geometry, and birefringence characteristics in curved anisotropic fibres     

复合材料结构等效电磁参数均匀化方法

依据周期结构复合材料等效电磁参数的均匀化方法,推导了此类结构等效电磁参数的有限元计算公式;并对介质框和介质方柱周期结构复合材料的等效介电常数进行了有限元求解,给出了这两类周期结构等效电磁参数的高精度拟合公式。数值算例表明这种有限元均匀化方法是可靠高效的,能够为周期结构复合材料的等效电磁参数预测和设计提供均匀化计算方法。     

Periodic bandgap and effective dielectric materials in electromagnetics: characterization and applications in nanocavities and waveguides

The main objectives of this paper are to characterize and develop insight into the performance of photonic bandgap (PBG) periodic dielectric materials and to integrate the results into some novel applications. A powerful computational engine utilizing the finite-difference time-domain technique with periodic boundary conditions/perfectly matched layers integrated with Prony's method is applied to provide an in-depth look at the physics of PBG/periodic bandgap structures. Next, the results are incorporated into two classes of applications in the areas of nanocavity lasers and guidance of electromagnetic (EM) waves in sharp bends. A two-dimensional PBG structure with finite thickness is presented to strongly localize the EM waves in three directions and design a high-Q nanocavity laser. It is shown that the periodic PBG/total internal reflections remarkably trap the EM waves inside the defect region. The effect of the number of periodic cells and defect's dielectric constant on the Q of structure is investigated. It has been found that a seven-layer PBG with a dielectric impurity defect can be used in the design of a laser with a Q as high as 1050. Additionally, potential applications of the PBG structures for guiding the EM waves in sharp bends, namely, 90/spl deg/ and 60/spl deg/ channels are demonstrated. It is shown that shaping the bend by introducing small holes can noticeably improve the guidance of the waves at the bends and channel the EM waves with great efficiency. A comparative study between PBG and effective dielectric materials in controlling the EM waves is also provided and it is observed that the novel characteristics of the PBG cannot be modeled using the effective material for the frequencies within the bandgap.