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.     

Perturbations impulsionnelles créées par des câbles ďénergie sur des câbles de transmission de données

This paper presents the study of coupling between multiconductor cables from the multiconductor lines theory and the assumption of perfectly conducting ground. The cables can be excited by generators of arbitrary waveforms and terminated by arbitrary impedances. The medium surrounding the conductors can be homogeneous or inhomogeneous and the conductors can have finite conductivity. Once the used assumptions indicated, we formulate the complete solutions of induced currents and voltages at the ends of the multiconductor line, by using the state variable theory. We give numerous comparisons of numerical results, obtained by our numerical code, with literature (microstrip lines) and experimental results (shielded cables, unshielded RNIS bus).     

Deterministic modeling of the (shielded) outdoor power line channel based on the multiconductor transmission line equations

In this paper, a complete methodology is proposed for the deterministic modeling of the channel transfer functions associated with underground power line access networks, in the light of the Multiconductor Transmission Line Theory. Some multiconductor power line cables are analyzed in detail, and their fundamental propagation characteristics (definition of eigenmodes, phase velocity, characteristic impedance, lineic attenuation) are related to the geometry of the conductors and the material properties. A multidimensional scattering matrix formalism is then introduced to perform an accurate analysis of the global power line network including multiconductor cable segments, derivation points, and termination loads. An illustrative example of a power line access network with three types of cables (with different numbers of conductors), 20 derivations, and five remote terminals, is finally proposed.     

Admittance calculation of a slot in the shield of a multiconductortransmission line

The admittance calculation for a narrow slot in the conducting shield of a multiconductor transmission line (MTL) is presented. An approximate calculation is given for the admittance seen looking into a slot in the shield of a multiconductor transmission line when a uniform magnetic current is placed over the slot. The calculation presented is approximate in that only the transmission line mode is used in the calculation. All higher-order waveguide modes are neglected. This allows the magnetic current to be replaced by a point voltage source at the slot location. The admittance calculation then corresponds to calculating the driving point admittance of a point voltage source located in the shield of an MTL     

Coupled-mode formulation of multilayered and multiconductortransmission lines

A novel coupled-mode formulation for multilayered and multiconductor transmission lines is developed. In this formulation, the solutions to the original multiconductor system are approximated by a linear combination of eigenmode solutions associated with the isolated single conductor line located in an appropriate reference dielectric medium. The reciprocity theorem is used to derive the coupled-mode equations. The coupling coefficients are expressed in terms of the simple overlap integrals between the eigenmode fields and currents of the individual conductor lines. As a basic application, the dispersion characteristics of two identical coupled-microstrip lines are analyzed using the proposed coupled-mode theory. It is shown that the results are in very close agreement with those obtained by the direct Galerkin's moment method over a broad range of weak to strong coupling     

Isolation effects in single- and dual-plane VLSI interconnects

The issue of interline coupling in high-speed VLSI interconnects is addressed. A full-wave-based technique is used to numerically solve for the modes and hence the line voltages and currents for multiconductor microstrip. The accuracy of these results is compared with time-domain experimental data. Isolation lines placed between signal lines and grounded at both ends are considered as a means of significantly reducing crosstalk. It is shown that the performance of such lines depends on several factors such as relative mode velocities, signal rise and fall times, and line length. These points are illuminated by considering the effects of isolation lines in two geometries of interest in high-speed integrated circuits. On the basis of these results one can determine the usefulness of isolation lines for a given geometry     

Prediction of Crosstalk in Ribbon Cables: Comparison of Model Predictions and Experimental Results

The prediction of crosstalk in ribbon cables is investigated. Experimental results are obtained for a 20-wire ribbon cable and compared to the predictions of the multiconductor transmission line (MTL) model. Based on the experimental configuration tested, it would appear that accurate predictions of crosstalk can be achieved in these controlled-characteristic cables. The prediction accuracies are typically within ±1 dB for frequencies such that the line is electrically short and ±6 dB for frequencies such that the line is electrically long. It was found that the parasitic wires in the cable can have a significant effect (as much as 40 dB) on the coupling between a generator circuit and a receptor circuit in the cable. Therefore, to achieve accurate predictions in ribbon cables, one must consider the interactions between all wires in the cable. The wire insulation evidently cannot be ignored for frequencies such that the line is electrically long. The impedance of the reference wire cannot be ignored for low frequencies where the common-impedance coupling dominates the electromagnetic-field coupling.     

Computation of Crosstalk in a Multiconductor Transmission Line

Closed-form solutions for the terminal currents of a multiconductor transmission line are obtained. The results allow a numerically efficient computation of the crosstalk associated with an (n + 1)-conductor line when a large number of frequencies are of interest and bypass the usual requirement for the repeated solution of n simultaneous equations at each frequency. The results show the effect of parasitic circuits in the line on the coupling between any two circuits. It is also shown that the usual low-frequency notion of superimposing inductive and capacitive coupling which has been used for lines with only two circuits is valid, for an electrically short line and a sufficiently low frequency, for a multiconductor line containing any number of coupled circuits. Some additional qualitative details concerning the crosstalk are evident in this formulation.     

多芯片组件带网孔接地板多导体互连线结构的电磁特性分析

本文给出一基于准静态场的直线法,来分析多芯片组件（ＭＣＭ）带有网孔接地板的多层多导体互连线结构的分析方法,以此提取等效传输线的特性参数。最后给出几个实例的计算结果。     

Analysis of Lossy Transmission Lines with Arbitrary Nonlinear Terminal Networks

A novel method for transient analysis of Iossy transmission lines with arbitrary nonlinear terminal networks is presented. The uniqueness of this approach is that we develop time-domain Green's functions for the multiport transmission-line systems by terminating the ports in quasi-matched loads. This ensures Green's functions of a short duration. Hence, the amount of frequency-domain data necessary to obtain time-domain Green's functions is modest. These Green's functions are then convolved with the line port voltages. With this technique one can analyze responses of multiconductor transmission lines with arbitrary nonlinear loads (even with memory) as we have at any instant of time Thévenin's equivalent of the linear portion of the system. An example is presented to illustrate the application of this technique to multiconductor nonlinearly loaded transmission lines.     

Coupled mode analysis of forward and backward coupling in multiconductor transmission lines

The nonorthogonal coupled mode theory is extended to the analysis of multiconductor transmission lines by including backward coupling. Coupling coefficients are expressed as overlap integrals of the eigenfields and currents belonging to individual lines. These eigenmode solutions are calculated using the finite-difference time-domain method, which can provide a broadband solution through a single simulation. General termination conditions are given, and scattering parameters of a multiconductor transmission line can be obtained directly by solving the coupled mode equations subject to these termination conditions. As illustrative examples, several configurations of coupled microstrip lines are analyzed, and numerical results are presented. It is observed that both the forward and backward coupling results agree fairly well with results from Advanced Design System Momentum software.     

圆柱腔内多导体传输线的瞬态电磁响应

为提高系统抗强电磁脉冲毁伤能力,采用时域有限差分法(Finite Difference Tim e Domain,FDTD)和通用电路仿真器(SPICE)相结合的协同仿真方法,以圆柱腔内由单导线、 双绞线、普通双线和同轴线组成的线束为研究对象,重点研究了导线类型、导线间距、捆扎 和RC滤波电路对耦合特性的影响。结果表明：耦合系数受腔体和传输线的双重影响,同轴线 耦合系数较其他两类线缆降低约40 dB;线间相互屏蔽是捆扎降低耦合系数的主要原因 ;随着导线间距增大,耦合系数幅值增大;RC滤波电路是降低电磁耦合的有效手段。所得结 论对电子系统进行抗电磁脉冲加固具有重要意义。     

Modeling of magnetic-field coupling with cable bundle harnesses

A field-to-line coupling model is developed for cable bundle harnesses in terms of the scattering currents and total line voltages. The equivalent distributed sources representing the effects of electromagnetic coupling are expressed as a function of the incident magnetic-field components. Such a formulation is particularly suitable to be used for the analysis of multiconductor transmission lines excited by a transient field, when data for the incident electric field are either inaccurate or not available. This model allows the accurate calculation of the induced voltages and currents on complex cable bundles. The effects on the induced voltages and currents due to ground losses and to the presence of the dielectric sheath in shielded and unshielded cables is discussed, considering bundles excited by either slow or fast transient fields. Numerical applications demonstrate the validity of the proposed procedure.     

An electromagnetic model for multiconductor connectors

An electromagnetic model for the response of multiconductor connectors is presented. The model is based on the canonical problem of the electromagnetic response of a thin circumferential slot in the shield of a cylindrical multiconductor transmission line (MTL). The problem is formulated for a shielded MTL of arbitrary cross section with impressed sources driving the interior of the MTL. The problem of interior-to-exterior coupling is solved by treating the slot as a thick aperture in the shield. The equivalence principle is used to divide the original problem into three separate parts. Two coupled integral equations are obtained for the equivalent surface magnetic currents, which are solved by the method of moments, and equivalent networks are presented. The equivalent networks consist of three generalized admittances, one of which is interpreted in terms of a connector admittance     

Time-domain analysis of lossy multiconductor transmission lines based on the Lax–Wendroff technique

Taking advantage of the hyperbolic characteristics of the telegrapher equations, this paper applies the Lax–Wendroff technique, usually used in fluid dynamics, to transmission line analysis. A second-order-accurate Lax–Wendroff difference scheme for the telegrapher equations for both uniform and nonuniform transmission lines is derived. Based on this scheme, a new method for analyzing lossy multiconductor transmission lines which do not need to be decoupled is presented by combining with matrix operations. Using numerical experiments, the proposed method is compared with the characteristic method, the fast Fourier transform (FFT) approach, and the Lax–Friedrichs technique. With the presented method, a circuit including lossy multiconductor transmission lines is analyzed and the results are consistent with those of PSPICE. The nonlinear circuit including nonuniform lossy multiconductor transmission lines is also computed and the results are verified by HSPICE. The proposed method can be conveniently applied to either linear or nonlinear circuits which include general transmission lines, and is proved to be efficient.     

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.     

Experimental Characterization of Multiconductor Transmission Lines in the Frequency Domain

Although a number of papers have been published on the experimental characterization of multiconductor transmission lines, they are limited to the time domain for lossless multiconductor lines in homogeneous media. This paper presents a method for the characterization of multiconductor transmission lines in inhomogeneous media. The experimental technique for the measurement of multiconductor line parameters is presented and the appropriate multiconductor line equations are solved to obtain these parameters. The experimental method involves only the short-and open-circuit impedance measurements for different configurations. The experimental results for a four-conductor line are found to be in good agreement with computed results and a low-frequency lumped model.     

端接非线性负载的不等长传输线瞬态分析

对时域有限差分(FDTD)法应用于不等长多导体传输线端接非线性负载的情况进行了介绍.首先给出了多导体传输线电报方程和差分公式;然后介绍了不等长传输线的仿真模型;在此基础上,最后通过建立端接非线性负载的不等长多导体传输线模型,对该情况下传输线两端的电压响应进行了分析.数值仿真结果说明了FDTD法解决此类问题的正确性和有效性,为不等长传输线瞬态分析的进一步研究打下了基础.     

Perturbations induites par une onde de foudre sur un réseau de câbles blindés aériens

In this work we study the coupling of a lightning wave with an overhead shielded cables network. The study is led directly in the time domain with hold in account of the loads nonlinear character, and the effect of a finite conductivity of the shield and soil. After discretization by the method so-called FDTD (Finite Difference Time Domain) of the lines equations excited by a lightning wave and the application in every node of the network of the Kirchhoff’s laws in current and voltage, we deduct a equations system linear or no, of which the resolution permits us to deduct the induced electric quantities in every node of the network. In this study we propose a concept for the coupling analysis of a lightning wave with a shielded cable without use of the least FFT; the shielded cables are treated in a single stage. In this work we also put in evidence the disadvantages of the coupling analysis in the frequency domain.     

多导体传输线互耦实验研究

对多导体传输线的参数进行了测量,分析了误差的原因,并对多导体传播输线的瞬态响应进行了实验研究,讨论了负载与传输线瞬态响应的关系。