基于高阶辛算法的纳米器件本征问题仿真

研究精确和高效的数值方法是现代纳米器件建模和优化的重要目标之一,而分析大部分纳米器件特性的切入点是确定器件结构的能量本征值和能量本征态。本文提出了一种新的算法—高阶辛时域有限差分法(SFDTD(3,4): symplectic finite-difference time-domain)求解含时薛定谔方程。在时间上采用三阶辛积分格式离散,空间上采用四阶精度的同位差分格式离散,建立了求解含时薛定谔方程的高阶辛时域有限差分算法。将高阶辛算法SFDTD(3,4)用于一维量子阱中盒中粒子和谐振子的仿真中,实验结果表明SFDTD(3,4)法比传统的时域有限差分算法以及高阶时域有限差分算法更加准确,适用于对纳米器件本征问题的长时间仿真。     

时域有限差分法在天线和微波技术中的应用（上）

介绍了目前正在迅速发展和应用范围非常广泛的一种电磁理论的数值计算方法－时域有限差分法（ＦＤＴＤＭ）的基本理论：Ｙｅｅ的算法（它是将问题的解域离散化成直角立方体网格，并将直角坐标系中的Ｍａｘｗｅｌｌ旋度方程用有限差分方程来代替，然后在相应的边界和初始条件下解有限差分方程的一种新型的数值计算方法）以及在Ｙｅｅ算法基础上的很多扩展的理论方法。给出了它们在电磁理论方面的广泛应用。最后提出了ＦＤＴＤ方法对计     

电磁计算在雷达设计中的应用及需求分析

随着计算电磁学和计算机技术的迅速发展,电磁计算在雷达设计中扮演着举足轻重的角色.本文分析了电磁计算在雷达设计中的应用,包括雷达天线设计、馈线及微波网络设计、天线罩设计以及复杂电磁环境雷达天线性能评估,并介绍了有限元法（finite element method,FEM）、矩量法（method of moment,MoM）和时域有限差分（finite-difference time-domain,FDTD）法三种常用的全波电磁仿真计算方法以及高频近似算法,最后讨论了雷达技术发展对电磁计算的新需求.     

用FD—TD方法对微带天线的时域电磁仿真

本文运用时域有限差分（FD-TD）法，对微带天线的电磁特性进行时域仿真。首先是对算法的原理介绍及其在仿真软件中具体实现方法作概要说明；然后分别阐述仿真解在时域和频域中的各项应用；最后，采用该仿真技术，实例分析若干天线性能，使之成为微带天线工程设计中一种方便经济的辅助手段。     

外场作用双导线的电磁耦合时域分析方法

基于时域有限差分（finite-difference time-domain，FDTD）法和传输线方程，并结合插值技术，研究了一种高效的时域混合算法，能够快速模拟电磁波照射自由空间和屏蔽腔内双导体传输线的电磁耦合，并实现空间电磁场与双导线瞬态响应的同步计算.该算法先采用FDTD方法模拟双导线周围空间的电磁场分布，结合插值技术构建适用于双导线电磁耦合的传输线方程，再采用FDTD的中心差分格式进行离散，从而求解得到传输线和端接负载上的瞬态响应.同时，分析双导线间距对其电磁耦合的影响，掌握其耦合规律.通过相应数值算例的模拟，并与FDTD方法进行对比，验证了该时域混合算法的正确性和高效性.     

一种分析微带贴片天线的辛时域有限差分方法

文中研究了在时间上采用5级4阶差分、空间上采用4阶差分的高阶辛时域有限差9（SFDTD）数值方法。给出其三维差分公式．将吸收边界条件应用于微带天线的计算中，计算了微带贴片天线的回波损耗及输入阻抗等．计算结果证明，该方法的精确性和正确性．     

离散多频音调制中的时域均衡器的两种算法比较

对于设计一个DMT（离散多频音）系统来说，两种最关键的技术就是带宽优化算法的选择和前置时域均衡器的设计。文中就时域均衡器的设计，介绍了两种算法：基于迭代的TEQ（时域均衡器）算法和基于IDFT／DFT（离散傅里叶逆变换／离散傅里叶变换）的循环均衡算法，并且对两种算法进行了理论分析和计算机仿真，给出了仿真结果。     

基于辛算法海面与目标电磁散射研究

为了克服时域有限差分（FDTD）的缺陷我们引入辛算法理论（SFDTD）,结合辛算法的稳定性分析了海面与其上方目标的复合电磁散射特性,并分析了入射角度,风速等对复合散射特性的影响,首先给出了Weiersstrass分形海面模型,数值结果表明分维度和风速的变化都会引起海面的粗糙程度很大的变化,同时目标的存在对海面散射影响很大,它使得海面的散射能量会有相应的增加,并且风速的增大使得海面粗糙度增大,这样在其他方向上散射逐渐增强,而在镜像方向上的增强越来越不明显。     

复杂电大开口腔体的高功率微波防护分析

提出考虑传输衰减的高功率微波（HPM）激励模型,基于镀膜透明介质结构设计流程,给出了电磁透射率、反射率计算方法和厚度远低于网格尺寸的薄膜等效处理时域有限差分（FDTD）算法,设计了一种透明导电镀膜的介质屏蔽结构,建立复杂结构与电磁参数的真实三维飞机-飞行员模型,开展了电磁防护分析。仿真结果表明：采用电场幅度最值衰减和防护极限评估防护效果具有良好的工程适用性,且该屏蔽结构在一定载频范围内辐射防护效能好,防护极限高。     

金属孔阵Ku波段透波增强特性研究

用高稳定的辛时域有限差分算法(SFDTD)对金属周期孔阵在Ku波段的透波增强特性进行了研究.数值计算了金属板厚度、孔的大小、孔中填充不同折射率的介质和孔阵的周期等物理参数对孔阵透射系数的影响.得出的研究结果表明:金属周期孔阵在Ku波段的透射系数随孔的增大而增大,随孔阵周期的增大而减小,填充高折射率的介质有利于其透射.     

Envelope-finite-element (EVFE) technique - a more efficienttime-domain scheme

A novel technique, called the envelope-finite element (EVFE) method, is proposed as a more efficient full-wave time-domain modeling scheme of electromagnetic waves. The EVFE method simulates the signal envelope rather than the original signal waveform by de-embedding the signal carrier from the time-domain wave equation. The de-embedded equation is then solved in the time domain using finite-element methods based on Newmark-Beta time stepping. Compared to traditional time-domain simulation techniques such as finite difference time-domain or finite element time-domain methods, only the signal envelope needs to be sampled in EVFE simulation. This method can reduce computation time when signal envelope/carrier ratios are very small. The purpose of this paper is to introduce this new concept, by presenting the two-dimensional EVFE formulations, stability conditions, and some supporting numerical examples     

Circuit analysis of electromagnetic radiation and field couplingeffects for networks with embedded full-wave modules

With continually increasing operating frequencies, the analysis of electromagnetic interference (EMI)-related effects is becoming an important issue for high-speed designs. An algorithm is presented for fast analysis of radiation and incident field coupling effects in high-speed circuits. The proposed technique provides an efficient means for combining the solutions from full-wave field solvers such as the finite-difference time-domain (FDTD) method with circuit level simulators such as SPICE for calculating radiated/coupled fields in arbitrarily shaped interconnect structures. The technique speeds up the whole simulation process by employing a model-reduction-based approach, and also overcomes the numerical stability problems associated with the FDTD, in the presence of nonlinear terminations. In addition, the proposed algorithm provides a direct access to existing vast device libraries of SPICE in EMI analysis     

Calculation of radiated electromagnetic fields from cables usingtime-domain simulation

Radiated electromagnetic fields are produced by currents in cables or transmission lines interconnecting various circuits. An elegant method of computing the resultant electromagnetic field, produced by several radiating current elements, is given. The current in each radiating cable is first found from a time-domain simulation algorithm and this may be a steady-state or transient current. The radiated field is then calculated by assuming that a radiating transmission line can be treated as a chain of short radiating dipoles. The problems associated with the calculation of the near-zone term at low frequencies and the overall response near the radiator are clarified. The proposed technique is fully evaluated and compared with other methods     

Analysis of curved and angled surfaces on a Cartesian mesh using anovel finite-difference time-domain algorithm

The widely accepted finite-difference time-domain algorithm, based on a Cartesian mesh, is unable to rigorously model the curved surfaces which arise in many engineering applications, while more rigorous solution algorithms are inevitably considerably more computationally intensive. A nonintensive, but still rigorous, alternative to this approach has been to incorporate a priori knowledge of the behavior of the fields (their asymptotic static field solutions) into the FDTD algorithm. Unfortunately, until now, this method has often resulted in instability. In this contribution an algorithm (denoted `SFDTD' for second-order finite difference time domain) is presented which uses the static field solution technique to accurately characterize curved and angled metallic boundaries. A hitherto unpublished stability theory for this algorithm, relying on principles of energy conservation, is described and it is found that for the first time a priori knowledge of the field distribution can be incorporated into the algorithm with no possibility of instability. The accuracy of the SFDTD algorithm is compared to that of the standard FDTD method by means of two test structures for which analytic results are available     

Application of the spatial finite-difference and temporaldifferential (SFDTD) formulation to cylindrical structure problems

The recently developed spatial finite-difference and temporal differential (SFDTD) approach is extended to dielectric loaded cylindrical environments. Although the method is developed differently, its resultant formulation can be directly obtained from the corresponding finite-difference time-domain (FD-TD) method. Good agreements between the SFDTD and reference results are obtained for different configurations of dielectric loaded cylindrical structures. As a result, the SFDTD approach is shown to be generally effective and robust for resonant structures     

Finite-difference time-domain simulation of ground penetratingradar on dispersive, inhomogeneous, and conductive soils

A three-dimensional (3D) time-domain numerical scheme for simulation of ground penetrating radar (GPR) on dispersive and inhomogeneous soils with conductive loss is described. The finite-difference time-domain (FDTD) method is used to discretize the partial differential equations for time stepping of the electromagnetic fields. The soil dispersion is modeled by multiterm Lorentz and/or Debye models and incorporated into the FDTD scheme by using the piecewise-linear recursive convolution (PLRC) technique. The dispersive soil parameters are obtained by fitting the model to reported experimental data. The perfectly matched layer (PML) is extended to match dispersive media and used as an absorbing boundary condition to simulate an open space. Examples are given to verify the numerical solution and demonstrate its applications. The 3D PML-PLRC-FDTD formulation facilitates the parallelization of the code. A version of the code is written for a 32-processor system, and an almost linear speedup is observed     

Time-domain modeling of electromagnetic wave interaction with thin-wires using TLM

A method for the time-domain simulation of electromagnetic (EM) wave interaction with thin-wires is developed. The technique is based on the standard transmission-line modeling (TLM) technique augmented with systems derived from the telegrapher's equations to represent the propagation of currents in wires. Full details of the numerical algorithms are given and examples are shown to illustrate the application of the technique to typical electromagnetic compatibility (EMC) problems.     

采用粒子群算法的频率选择表面优化设计

 粒子群优化算法作为优秀的群体智能算法之一,已经被广泛应用于电磁优化问题中.通过与时域有限差分(FDTD)算法相结合,粒子群优化算法被运用于频率选择表面的优化设计.在此过程中,通过使用图形处理器(GPU)加速技术将FDTD算法速度提高近100倍,配合FDTD的宽频特性显著加速了优化过程.在此基础上,针对给定单元结构以及未知单元结构两种频率选择表面设计情况,分别采用带惯性权重的粒子群优化算法以及二进制离散粒子群优化算法进行优化.提出的两种优化流程在算例中得到验证与分析,证明了其可行性及高效性.     

利用时域散射场进行目标方位探测研究

为充分地开发电磁场时域响应数据中潜在的大量有用信息,提出一种新颖的仿真算法,将阵列信号处理技术应用到对电磁场时域响应的后处理中,可以确定目标的方位和距离,以及探测浸没在某种背景下的目标.通过时域有限差分法(FDTD)与MUSIC方法相结合,实现了具体的数值模拟,从而证明利用阵列信号处理技术能够从电磁场时域响应当中获得潜在信息,同时两者结合可以构成更为完善的数值模拟.