任意方向细导线的FDTD算法

给出了计算任意方向细导线问题的一种FDTD算法.该算法通过电报方程对细导线建模,将细导线和三维场分离,再利用插值处理细导线和场的互耦问题.通过数值例子,对该算法的有效性进行了分析讨论.     

贯通导线端接负载对腔体电磁耦合影响分析

为研究贯通导线端接负载对金属腔体电磁耦合的影响,基于时域有限积分方法建立了平面波辐射条件下含贯通导线金属腔体的耦合计算模型,通过腔内屏蔽效能变化研究了端接负载及连接方式等对腔内电磁耦合的影响,分析了耦合机理,提出了基于吉赫横电磁波传输室建立含贯通导线腔体电磁耦合实验的新方法,对计算结果进行了实验验证.研究表明:腔内贯通导线负载为纯电阻及容性阻抗时,负载接腔体或腔体接地能降低腔内的电磁耦合,且电阻值及电容值大小对腔内耦合有显著影响;电阻及加载电容后发现,负载开路且腔体不接地时,腔体的低频电磁耦合效果基本不变,负载短路且腔体接地时,负载变化对腔内高频耦合影响不大.负载连接腔体对腔内电磁耦合的谐振频率有一定影响.     

贯通导线端接负载对腔体电磁耦合影响分析

为研究贯通导线端接负载对金属腔体电磁耦合的影响, 基于时域有限积分方法建立了平面波辐射条件下含贯通导线金属腔体的耦合计算模型, 通过腔内屏蔽效能变化研究了端接负载及连接方式等对腔内电磁耦合的影响, 分析了耦合机理, 提出了基于吉赫横电磁波传输室建立含贯通导线腔体电磁耦合实验的新方法, 对计算结果进行了实验验证.研究表明:腔内贯通导线负载为纯电阻及容性阻抗时, 负载接腔体或腔体接地能降低腔内的电磁耦合, 且电阻值及电容值大小对腔内耦合有显著影响; 电阻及加载电容后发现,负载开路且腔体不接地时, 腔体的低频电磁耦合效果基本不变, 负载短路且腔体接地时, 负载变化对腔内高频耦合影响不大.负载连接腔体对腔内电磁耦合的谐振频率有一定影响.       

基于光纤光栅温度传感器的导线负载检测系统

在电流回路中,当通过导线的电流过高时,会导致线路高温,严重时可能引起火灾。因此实时监测电流线路的温度,对预防线路过载以及火灾的发生具有重要的意义。在理论分析光纤光栅温度传感机理的基础上,设计了用于导线负载检测的传感系统。在0~5 A范围内,实验研究了光纤光栅温度传感器中心波长变化与导线负载之间的关系,验证了导线负载检测的可行性,为导线负载的实时监测,以及断路、短路故障的判断提供了一种新的方法。     

考虑时间因素的不同基本门故障概率计算

在门级电路的可靠性概率评估方法中,基本门的故障概率p一般人为设定或以常数形式出现.考虑到不同基本门的故障概率具有随时间变化的特性并结合其输入导线,本文构建了考虑输入负载的随时间变化的不同基本门的故障概率模型.理论分析与实验结果表明,基于弱链接模型的双峰对数正态分布更适合用来表示输入导线故障概率的时间分布.用本文方法、美国军用标准MIK-HDBK-217及Monte Carlo方法计算了ISCAS85基准电路的可靠度并进行了比较,还通过了行业标准的检验,结果验证了本文所构建模型的合理性.     

平面波照射下贯通导线电磁干扰快速算法

提出了一种基于BLT（Baum-Liu-Tesche）方程的平面波辐照下金属腔贯通导线电磁干扰分析的快速计算方法.首先采用电磁拓扑理论将整个问题进行拓扑分解,根据场线耦合理论获得场线耦合节点的传输函数,进而采用广义BLT方程获得外界电磁波与贯通导线相互作用时金属腔内终端负载上的干扰电流.将该算法用于贯通单导线、贯通双导线和贯通传输线网络电磁干扰问题分析,计算获得的终端负载上感应电流结果与全波分析方法结果吻合较好,证明了该快速算法的有效性.该快速算法计算时间仅为全波分析法的万分之一,且所占内存相比全波分析法缩小了几十倍.     

对象存储系统中基于监控的动态负载均衡方法

负载均衡在存储系统领域一直是研究的热点,但在分布式的对象存储系统中的应用与实现方面仍存在缺陷.针对对象存储系统中负载均衡方法大都依靠经验或有限的动态配置指导自适应算法进行、在负载再平衡过程中无法控制迁移节奏,算法实现复杂,未充分考虑存储节点实时负载状况等不足,提出了一种基于监控的动态负载均衡方法.该方法将监控系统引入对象存储系统,完成对各存储节点负载状况的实时感知;根据节点负荷、异构性等因素进行综合估计来触发迁移算法,避免了依靠经验及预设值指导算法执行;利用监控系统灵活的自定义事件触发机制和故障自动化处理机制,设计负载迁移策略,动态完成节点间的负载再平衡,降低算法实现复杂难度;使用监控系统动作执行过程中的多步操作顺序流控制完成一次一迁移,有效掌控负载迁移节奏.将该方法应用到自主研发的对象存储系统CSCloud进行验证的结果表明,该方法能及时获取集群中各节点的负载信息,并实现及时、准确的动态负载平衡,为对象存储系统和其他分布式存储系统实现负载均衡提供了新思路.     

飞机开关负载传导干扰的测量方法

开关负载在飞机交流电网的导线上产生的干扰主要是传导干扰.对使用射频电流探头和线性阻抗稳定网络测量开关负载传导干扰的方法进行了介绍,并用matlab对线性阻抗稳定网络测量方法进行了仿真.这两种方法能够容易地测出共模与差模干扰.     

微带线匹配负载的FDTD建模

提出了一种有效的微带线端接匹配负载的FDTD模型.该模型将微带线的有效阻抗作为匹配负载电阻,然后按适当的比例分布到端接面的网格中.和传统的FDTD方法相比, 该模型可以有效地减少负载的反射,改善负载的匹配特性,并且通过一次FDTD计算就可以得到电路的S-参数.     

恒带宽窄带集总跳频滤波器的理论计算与实现

为了快速准确地设计并制作恒带宽窄带集总跳频滤波器,提出了一种随频率变化而变化的负载结构.通过对这种结构模型的分析,得到了其关于频率和相对带宽的精确变换公式,利用麦夸特优化法对其进行优化计算,快速得到该负载结构各部件的最优值.最后利用该方法设计并制作了一个二阶集总带通滤波器.实验结果表明,该方法实现滤波器比传统手调快几倍...     

一种分析异向介质中导线阵列宏观效应的新方法

本文根据异向介质中细导线阵列的电磁效应,利用均匀介质与均匀传输线的等效关系,建立起电磁波在导线阵列中传播时的等效电路,以此为依据从宏观上推导出异向介质中非均匀导线阵列的有效介电常数模型,在呈现出非常清晰的物理图景的同时,为人们从宏观物理学的角度理解导线阵列的等效负介电常数效应、从实质上揭示异向介质的构成理论向前跨进了一步.数值仿真结果表明,该模型具有足够的精度.本文所得到的结论对理解异向介质的构成提供了更加清晰的描述方法,为异向介质在微波电路领域的应用提供了一套分析方法.     

The near field of annular antennas

The circular loop antenna has been investigated by many authors beginning as early as 1897 with Pocklington's study of the thin wire loop excited by a plane wave. Later, both Hallen and Storer considered the case of driven antennas. All of these authors used a Fourier series expansion for the loop current, and the latter two found numerical difficulties with the approach. These difficulties, as pointed out by Wu, can be avoided by integration of the free-space Green's function over the toroidal surface of the wire. The theory developed here is an improvement on previous works because it specifically takes into account the finite dimension of the wire. Consequently, the range of validity for our solution extends to fatter wires than previously considered. Furthermore, some detail of the loop current around the cross section of the wire is revealed. The theory, if applied to thin wire loops, gives radiation admittances in excellent agreement with results obtained by previous investigators. The computations of the electromagnetic fields near resonant loops show that the electric field strength is larger by a factor of ten than previously published values. Experimental results validate the theory presented in the following sections.     

Analysis of the coupling of an incident wave with a wire inside a cavity using an FEM in frequency and time domains

This paper presents a numerical method based on finite elements in both the frequency and time domains for modeling the coupling of an incident wave with a conducting wire placed inside a metallic cavity having a small aperture. The method uses edge elements on tetrahedra for the electric field representation. The formulation can take into account thin wires as well as lumped elements. In the time-domain approach, the time derivatives are discretized by the Newmark method, which allows obtaining an unconditionally-stable scheme with second-order accuracy. Numerical results are provided to validate the presented method.     

An accurate thin-wire model for 3-D TLM simulations

Accurate modeling of thin wires in large-scale numerical electromagnetic simulations is very time consuming if fine meshing is adopted. Special treatments of such wires to allow their incorporation into relatively coarse meshes have lead to the development of thin-wire nodes for the transmission-line matrix (TLM) method. Previous models require the use of empirical factors. A novel thin-wire node is presented that is derived from rigorous field theory, requires no empirical factors and is shown to be highly effective. Moreover, virtually no computational overhead is incurred in the use of the new wire node.     

A novel delta gap source model for center fed cylindrical dipoles

A novel delta gap source model is presented which improves the convergence of the numerical solution of the electric field integral equation (EFIE) using thin wire theory. This delta source model yields a stable solution for the current at the source location, both computed and measured current distributions and input admittances for cylindrical monopole antennas are presented     

Modeling low-frequency electrode-type resistivity tools in invadedthin beds

The authors formulate and implement a numerical mode-matching (NMM) method to model electrode-type resistivity tools in invaded thin beds. The authors derive the low-frequency approximation of the Maxwell's equations to obtain the partial differential equation for the potential field. The new NMM program is validated by comparing the numerical results with those obtained from other dc programs. It is found that this new program is much faster than the program using the finite-element method (FEM), and hence is useful for routine interpretation of resistivity logs and for inversion     

The perfectly conducting wire grating: Computation of the diffracted field from Maxwell's equations and Hamilton's canonical system

A theoretical and numerical study of the perfectly conducting wire grating is presented. For both fundamental cases of polarization, we solve the Helmholtz equation rigorously without any physical simplifying assumption. The only approximations are due to the use of numerical techniques in the integration of a differential system. The wire cross section is to a large extent arbitrary. The interest of Hamilton's canonical equations in the numerical treatment of certain practical problems is shown. No doubt, certain ideas contained herein could be adapted for solving many other problems in electromagnetic theory.     

Aperture Excitation of a Wire in a Rectangular Cavity

The problem of determining the currents excited on a wire enclosed within a rectangular cavity is considered. The wire and cavity interior are excited by electromagnetic sources exterior to the cavity which couple to the cavity interior through a small aperture in the cavity wall. It is assumed that the wire is thin, straight, and oriented perpendicular to one of the cavity walls. An integral equation is formulated for the problem in the frequency domain using equivalent dipole moments to approximate the effects of the aperture. This integral equation is then solved numerically by the method of moments. The dyadic Green's function for this problem are difficult to compute numerically; consequently, extensive numerical analysis is necessary to render the solution tractable. SampIe numerical results are presented for representative configurations of cavity, wire, and aperture.     

有界波模拟器中线缆耦合测量与仿真的对比验证

为了分析电缆受外界电磁脉冲作用产生的感应电流,开展了屏蔽电缆表面电流辐照测量实验,并进行了理论计算.实验测量系统采用椭圆弧形过渡段有界波模拟器,通过对电流探头进行标定以及探头引入干扰的消除,得到了较好的测试数据.然后利用时域有限差分方法（Finite Difference Time Domain,FDTD)细线模型进行了数值仿真,该模型计算量小、简单易行.对比仿真结果和实测结果,二者吻合较好,证明了辐照测试方法的有效性.     

Root-mean-square measure of nonlinear effects to the transient response of thin wires

A root-mean-square (rms) measure of effect of nonlinear loading on the transient response of thin wires is proposed. The transient behavior of nonlinearly loaded wires is analyzed directly in the time domain. The problem is formulated via the space-time Hallen integral equation. The equation is solved by the space-time Galerkin Bubnov boundary element procedure. Numerical results for the transient response of a thin wire computed by a time domain code based on this method are compared with results obtained from a frequency domain code. Some illustrative numerical results for the spatial distribution of the rms values of time varying currents are also presented.