A Model for Currents and Voltages Induced Within Long Transmission Cables by an Electromagnetic Wave

A model is presented for determining the transient currents and voltages induced within a long coaxial cable by a uniform plane traveling wave whose variation with time may be specified. The cable may be located above or within a half-space lossy dielectric with the wave incident from the half-space lossless dielectric. This results in a model for either aerial or buried cables with the source of the wave located in the atmosphere. A method is also presented for generalizing the approach to more complex cables encountered in communication systems. A demonstration of the applicability of this model is presented by analyzing the response of a 0.375-in coaxial cable for both aerial and buried situations. An incident electromagnetic wave with a rectangular time domain waveform is used to demonstrate the transient response. This waveshape is adequate to clearly indicate the transient phenomena. It is found that voltage enhancement results in both aerial and buried cables when the incident wave approaches grazing incidence. This voltage enhancement can be significant especially for aerial cables. Cable shield current enhancement also results for an aerial but not for a buried cable.     

A numerical method for transient analysis of coupled antennas

A numerical method for finding the transient response induced on coupled thin cylindrical antennas excited by an electromagnetic pulse (EMP) is introduced. Numerical examples are given for two coupled thin antenna that are broadside incident by an idealized EMP. Applications of the method are made to calculate the induced currents on corner reflector antennas, and numerical examples are given to illustrate how the transient responses are modified by coupling effects. Examples of applying the method to include the effects of the time-varying medium on the responses are also shown with an assumed time-varying air conductivity.     

Bounding EMP interaction and coupling

A technique is presented for obtaining upper bounds of the voltages and currents at terminations on a wire which is excited by an incident electromagnetic wave coupled through an aperture. The internal interaction and coupling problems are considered. Upper bounds are developed for the power waves launched on the wire structure and the termination signal levels are bound with a term included for multiple reflections. Tighter bounds are obtained by separating the incident field into individual parts typically characterized by poles in the complex frequency domain.     

Transmission Line Mode Response of a Multiconductor Cable in a Transient Electromagnetic Field

This paper describes a technique for obtaining the induced worst case currents on individual wires of a multiconductor cable as a result of a transient electromagnetic radiation field. The technique involved a development of the expression for the induced current in matrix form where the mutual coupling terms and the other cable currents are the pertinent parameters. A worst case solution results from the assumption of maximum coupling orientation of the individual wires. A short example and some test results are presented. The test results show wave shapes for inductive and capacitive coupling. The solution for the individual wire current due to a transient electromagnetic field is important, since it will greatly reduce the required number of cable measurements and will allow the development of improved shielding techniques.     

On Reducing the Lightning Transients in Buried Shielded Cables Using Follow-On Earth Wire

This paper investigates the importance of a follow-on buried bare earth wire for the lightning protection of buried shielded cables. The use of follow-on bare wires for lightning protection of communication towers was suggested as a recommendation in certain standards, without being complemented either by theory or experiments. When lightning transients couple to the cable shields, it induces large currents (depending on the type of coupling) causing transient overvoltages between the inner conductors and the shield. It is shown by simulations based on multiconductor transmission line theory that if the follow-on bare earth conductor is placed in parallel with the shielded cable with the bare earth wire connected to the shield at the current injection end, then the shield current, and thereby, the internal transient voltages of the cable are reduced considerably.     

Transient response of a microstrip line circuit excited by anexternal electromagnetic source

The transient voltages and currents induced by an external electromagnetic field along a microstrip line interconnecting active and/or passive components are studied by using a distributed-source transmission-line model. The influence of the angle of incidence as well as that of the microstrip geometrical and electrical parameters on the line response is analyzed. The instantaneous voltage and power induced on the loads by various types of pulse excitations are computed. Numerical results are obtained both for dispersive and nondispersive lines. A line feeding a transistor microwave amplifier is also considered. The results show the effects of the multiple reflections of the field inside the dielectric substrate and of the signal at the ends of the line. Indications of how to reduce the coupling between the external field and the considered structure are given     

AH-FDTD方法在工程电磁耦合效应分析中的应用

电磁脉冲可通过对地下工程中的线缆和设备产生耦合，进而产生较大的瞬变电压和电流，导致电气系统出现故障或永久损坏.文中提出采用无条件稳定连带埃尔米特时域有限差分（associated Hermite FDTD，AH-FDTD）方法来分析场对地下工程的电磁耦合问题.建立了两种不同坑道模型（圆形和矩形），采用AH-FDTD方法计算了坑道不同深度、不同被覆层岩土介质（色散和有耗）和不同斜入射角度情况下地下工程中场的分布，分析了不同坑道埋深、不同岩土介质和入射角度等条件下场对坑道工程耦合的影响.研究表明，场对地下坑道工程的耦合与坑道埋深、是否考虑岩土介质的色散性以及入射角度大小有关，而受坑道形状的影响相对较弱.所提AH-FDTD分析方法为防护工程电磁耦合效应研究提供了一种新的途径.     

Calculation and experimental validation of induced currents on coupled wires in an arbitrary shaped cavity

An efficient numerical technique is presented for the calculation of induced electric currents on coupled wires and multiconductor bundles placed in an arbitrary shaped cavity and excited by an external incident plane wave. The method is based upon the finite-difference time-domain (FD-TD) formulation. The concept of equivalent radius is used to replace wire bundles with single wires in the FD-TD model. Then, the radius of the equivalent wire is accounted by a modified FD-TD time-stepping expression (based on a Faraday's law contour-path formulation) for the looping magnetic fields adjacent to the wire. FD-TD computed fields at a virtual surface fully enclosing the equivalent wire are then obtained, permitting calculation of the currents on the wires of the original bundle using a standard electric field integral equation (EFIE). Substantial analytical and experimental validations are reported for both time-harmonic and broad-band excitations of wires in free space and in a high-Qmetal cavity.     

Characterization of a cylindrical screen for external excitations and application to shielded cables

The main purpose of this paper is to present the definition of sets of parameters, which provide an intrinsic characterization of the shielding performances of a cylindrical generalized screen submitted to an external field. As examples, we detail two implementations of this approach, for the computation of the voltages induced by an incident field on a short section of a multiconductor shielded cable. More precisely, our approach is based on an expansion of the fields which may excite the generalized screen, into a combination of "standard excitations." They are defined in such a way that the shielding performances for a given standard excitation can be characterized in a simple manner, for instance, a single scalar parameter. In the case of shielded cables of electrically small cross section, this leads us to the rigorous introduction of the parameters for the "five main types of coupling," for which some experimental results have already been published. We then establish the exact induced current and voltage on a section of cable running above a ground plane, when an incident field propagates parallel to the ground plane, in the case of a longitudinal excitation, and in the case of a transverse excitation. We use these results to provide the value of the voltages at each end of a short section of cable characterized with the parameters for the five main types of coupling.     

Response of a planar microstrip line excited by an externalelectromagnetic field

The voltages and currents induced by external electromagnetic fields on a planar microstrip line have been studied with the use of a distributed-source transmission-line model. The frequency response of the microstrip line has been analyzed by simulating the illuminating field with a plane wave arbitrarily incident on the line. The influence of the microstrip geometrical and electrical characteristics on the voltages and currents induced on the line has been examined, and indications for reducing the circuit susceptibility have been obtained. The model adopted can be used for studying the response of the line to any type of external field arbitrarily varying in space time. Numerical results show that for lines loaded with the characteristic impedance at both terminals, voltage amplitudes on the order of some millivolts and currents of some hundreds of microamperes can be induced at f=3 GHz by an incident plane wave with an electric-field intensity of 1 V/m and for various angles of incidence. The voltages and currents induced on a microstrip circuit can be reduced by using substrates of sufficiently high permittivity     

Currents induced in a wire cross by a plane wave incident at an angle

The currents induced in a thin-wire cross with equal mutually perpendicular arms by an incident plane electromagnetic wave are determined when the normal to the wave front is perpendicular to the horizontal wire and is at an anglethetawith respect to the vertical wire; the direction of the electric vector in the wave front is arbitrary. The analysis is formulated in general terms but explicit formulas are obtained only for the zero-order currents which are generally adequate to determine the scattered field of very thin wires. The relatively simple formulas consist of even and odd parts for both the vertical and horizontal wires; they include components due to mutual coupling as well as those excited directly by the incident field.     

Scattering of TE-polarized EM wave by discontinuity in groundeddielectric layer

The two-dimensional problem of EM wave interaction with a dielectric discontinuity in an infinite grounded dielectric layer is studied. An electric field integral equation (EFIE) for TE illumination has been derived based on the Green's function for the electric field produced by induced polarization currents in the discontinuity region. Impressed electric fields consist of either plane waves incident from space above the dielectric layer or surface waves supported by that layer. Method of Moments (MoM) numerical solutions for the induced electric field in the discontinuity region are implemented. The amplitudes of surface waves excited by excess discontinuity-region polarization currents are calculated, as well as the pattern of the scattered field and the associated scattering width. It is observed that the excitation of a surface-wave mode reduces the back scattered radiation for TE-polarized plane wave incidence. The accuracy of the theory is verified by comparison of numerical results with those of existing studies     

Fast and Rigorous Analysis of EMC/EMI Phenomena on Electrically Large and Complex Cable-Loaded Structures

A fast and comprehensive time-domain method for analyzing electromagnetic compatibility (EMC) and electromagnetic interference (EMI) phenomena on complex structures that involve electrically large platforms (e.g., vehicle shells) along with cable-interconnected antennas, shielding enclosures, and printed circuit boards is proposed. To efficiently simulate field interactions with such structures, three different solvers are hybridized: (1) a time-domain integral-equation (TDIE)-based field solver that computes fields on the exterior structure comprising platforms, antennas, enclosures, boards, and cable shields (external fields); (2) a modified nodal-analysis (MNA)-based circuit solver that computes currents and voltages on lumped circuits approximating cable connectors/loads; and (3) a TDIE-based transmission line solver that computes transmission line voltages and currents at cable terminations (guided fields). These three solvers are rigorously interfaced at the cable connectors/loads and along the cable shields; the resulting coupled system of equations is solved simultaneously at each time step. Computation of the external and guided fields, which constitutes the computational bottleneck of this approach, is accelerated using fast Fourier transform-based algorithms. Further acceleration is achieved by parallelizing the computation of external fields. The resulting hybrid solver permits the analysis of electrically large and geometrically intricate structures loaded with coaxial cables. The accuracy, efficiency, and versatility of the proposed solver are demonstrated by analyzing several EMC/EMI problems including interference between a log-periodic monopole array trailing an aircraft's wing and a monopole antenna mounted on its fuselage, coupling into coaxial cables connecting shielded printed circuit boards located inside a cockpit, and coupling into coaxial cables from a cell phone antenna located inside a fuselage.     

飞机雷击附着区域的划分仿真研究

为了进一步提高飞机舱内电子设备对雷电间接效应的防护能力, 依据SAE-ARP5412等相关标准的规定, 以飞机舱内电子设备所在位置的电磁环境为研究对象, 建立了雷击时飞机舱内电磁环境的仿真模型, 对仿真参数进行了设置.仿真比较了雷击飞机时不同舱室内的耦合场, 并获得了舱内电子设备所接线缆的瞬态耦合电流.仿真结果表明:同一放电通道下驾驶舱内的耦合场最强; 舱门处定义了缝隙结构以后, 舱门附近的电场和磁场强度都增大; 同轴线缆有较好的屏蔽效能, 在飞机遭受雷击时, 可以有效避免芯线产生较大的瞬时感应电流研究结果对飞机舱内电子设备的雷电防护具有一定的指导意义.     

高空核爆电磁脉冲E2部分对架空管道的影响

高空核爆电磁脉冲会通过管道的耦合作用,对各种电子设备和系统造成严重的影响和破坏.为了研究高空核爆电磁脉冲对架空管道的影响,首先通过麦克斯韦方程给出了高空核爆电磁脉冲对架空管道的耦合方程,然后应用格林函数法求解微分方程得到管道上感应电流和电压的频域表达式,再应用傅里叶反变换得到电流和电压的时域波形.最后计算了基于IEC标准波形的高空核爆电磁脉冲E₂部分作用下架空管道的感应电流和电压.     

Susceptibility analysis of wiring in a complex system combining a3-D solver and a transmission-line network simulation

This paper deals with the application of electromagnetic field-to-transmission-line coupling models for large cable systems analysis. It emphasizes the use of Agrawal's (1980) model applied here in a numerical simulation of an electromagnetic susceptibility problem up to 500 MHz. Based on the concepts of EM topology, the proposed methodology consists in calculating the incident fields with a three-dimensional (3-D) computer code and the coupling on cables with a multiconductor transmission-line network computer code. In order to validate the efficiency of this methodology in an industrial context, an experiment has been performed on a prototype wiring installed in a Renault Laguna car, stressed by an EM plane wave. Numerous validation configurations have been carried out. First, the prototype cable network under study has been tested on a ground plane to validate the coupling model but also, to validate the cable-network topology itself. Second, EM fields have been measured onto the structure and inside the structure. Then, they have been compared to 3-D calculations, performed with an FDTD code. Third, comparisons between measurements and calculations of bulk currents and voltages on 50 Ω loads on the wiring have been achieved     

Steady-state and shock currents induced by ELF electric fields in ahuman body and a nearby vehicle

Steady-state currents induced in a human body and a nearby car by 60-Hz electric field of a high-voltage power line are determined, taking into account the coupling between the body and the car. The equivalent circuits for the body and the car are constructed on the basis of their calculated open-circuit voltages and short-circuit currents. A theoretical model and a method for predicting the shock current that may flow between the body and the car are developed using their equivalent circuits. The theory is verified by existing experimental results     

Scattered EM Field Responses of Canonical Scatterers Illuminated by an Impulse-Radiating Antenna (IRA)

This paper investigates the possibility of using the impulse-radiating antenna (IRA) as both a transmitter and receiver of electromagnetic energy for the purpose of target identification. Of specific interest is estimating the induced open-circuit voltage at the IRA's source terminals, when it is illuminated by the scattered EM field from simple conducting bodies excited by an incident field from the same IRA acting as a transmitter. In this study, several different canonical scatters are considered, including thin wires, spheres, conducting boxes, and an infinite conducting plate. For a 7 kV pulse excitation of the IRA, received peak transient voltages at the antenna ranged from a few volts to about 400 volts, depending on the scatterer.     

传输线端接复杂电路的电磁耦合时域分析方法

该文基于时域有限差分(FDTD)方法和传输线方程,结合Ngspice软件,提出一种高效的时域混合算法,能够快速模拟空间电磁场作用传输线端接复杂电路的电磁耦合问题。该算法的优势在于实现了空间电磁场辐射与端接复杂电路瞬态响应的协同计算,且避免了对传输线和复杂电路结构的直接建模。首先,将复杂电路通过传输线的特性阻抗进行等效,采用FDTD方法结合传输线方程,求解得到特性阻抗上的入射电流响应。然后,在每个时间步上,将该电流引入复杂电路作为激励源,联合电路模型建立网表文件。最后,使用Ngspice软件读取网表文件,并仿真得到电路各元件上的瞬态响应。通过相应计算实例的数值模拟,与电磁场仿真软件CST的计算结果以及耗用内存和时间进行对比,验证了算法的正确性和高效性。     

Model for estimating radiated emissions from a printed circuit board with attached cables due to Voltage-driven sources

Common-mode currents induced on cables attached to printed circuit boards (PCBs) can be a significant source of unintentional radiated emissions. This paper develops a model for estimating the amount of common-mode cable current that can be induced by the signal voltage on microstrip trace structures or heatsinks on a PCB. The model employs static electric field solvers or closed-form expressions to estimate the effective self-capacitances of the board, trace, and/or heatsink. These capacitances are then used to determine the amplitude of an equivalent common-mode voltage source that drives the attached cables. The model shows that these voltage-driven common-mode cable currents are relatively independent of the cable parameters and the trace or heatsink location when the PCB is small relative to the cable length and to a wavelength.