Fast Analysis of External Field Coupling to Orthogonal Interconnections in High-Speed Multilayer MMICs

Microstrip transmission lines in the proximity of each other are not always in parallel directions. In this paper, a fast method is proposed to determine the coupling of the external incident fields on the terminals of orthogonal interconnections embedded in multilayered media in the 1- 20 GHz frequency range. Because of the weak coupling between the lines, the effect of the incident plane wave is studied by applying standard Baum-Liu-Tesche equations separately for each interconnection. Later, the coupling between the lines is applied to terminal voltages by the use of a predetermined capacitance circuit model of the cross region. The experimental validation is also presented to verify the obtained results.     

高速电路PCB中串扰的仿真分析与抑制对策

针对串扰在高速电路印刷电路板(PCB)设计中造成严重的信号完整性问题,介绍一种可尽早发现串扰引起的问题的方法。首先利用信号完整性仿真软件HyperLynx,建立两条攻击线夹一条受害线的三线平行耦合串扰仿真模型;然后通过仿真分析传输线平行耦合长度、平行耦合间距、传输线类型、信号层与地平面层之间的介质厚度等因素对串扰噪声的影响;最后综合这些影响因素,并根据PCB设计顺序,给出抑制串扰的详细措施。实践表明,这些措施对高速PCB的设计,具有实用、可靠和提高设计效率的意义。     

Evaluation of closed-form crosstalk models of coupled transmissionlines

Closed-form crosstalk models used for the estimation of near and far end crosstalk voltages between two parallel transmission lines are evaluated. The quantitative validity ranges, in terms of transmission line length and coupling strength, of the crosstalk models are presented. It is shown that the accuracy of the commonly used closed-form crosstalk models deteriorates as the increase of the coupling strength and the line length     

Symbolic solution of the multiconductor transmission-line equationsfor lines containing shielded wires

The multiconductor transmission line equations that characterize crosstalk in a multiconductor transmission line containing a shielded wire are solved in symbolic form, that is, the resulting crosstalk voltages are determined in terms of symbols rather than numerical values. The resulting solutions show the frequency range for which the widely used, low-frequency, inductive-capacitive coupling model is a valid representation. The solution shows that the inductive-capacitive coupling model is an adequate characterization of crosstalk for lines that are electrically short and whose termination impedances do not differ substantially from the characteristic impedances of the lines that are involved. For lines whose termination impedances differ drastically from the line characteristic impedances, the inductive-capacitive coupling model is valid only for frequencies where the line is extremely short, electrically. For higher frequencies of excitation, the model may give predictions that are substantially below the true crosstalk even for frequencies where the line is electrically short     

Analysis of crosstalk between finite-length microstrip lines: FDTDapproach and circuit-concept modeling

Two approaches, one based on the circuit concept and the other based on field theory, are used to model the crosstalk between two microstrip lines of finite length and arbitrary orientation. In the circuit-concept modeling, a set of equations for the line voltages and currents has been derived from a modified telegrapher's equation. A four-port network expression is resultantly obtained by solving the equations, thus the crosstalk can be predicted by applying terminal conditions to the network expression. On the other hand, the extended finite-difference time-domain (FDTD) method has been used to model the terminal resistors and the feeding resistive voltage source in the crosstalk analysis. Several physical models have been fabricated and experiments performed. The calculated results are compared to measurements. In our experiment, for microstrip lines of finite length and arbitrary orientation, there are short line-sections or vias at each of the four ports, which should be incorporated into the crosstalk analysis. This effect has been investigated numerically and experimentally     

串扰耦合的低频分析有效性及阻抗特性研究

从传输线模型出发，分析了二平行直导线间串扰的低频模型有效性，得出允许3dB误差的条件下，低频模型在工程计算串扰中的电学短线和频率足够小的具体限值；同时分析了端接阻抗大小对串扰耦合的影响。对电磁兼容性中的串扰耦合的工程应用有实际指导和参考意义。     

非均匀传输线间的串扰研究

应用时域有限差分法对非均匀传输线间的串扰耦合进行分析。基于细线散射的时域有限差分法分析非均匀结构时,采用阶梯式均匀传输线模型,对非均匀传输线进行分段逼近。针对不等长、线径变化、非平行线和交叉线4种情况分析其参数变化对串扰的影响。研究表明：不等长电缆超出部分长度对串扰耦合幅度影响较小,对谐振频率影响较大;电缆线径的变化对其串扰耦合影响较小;非平行线和交叉线的角度对电缆间串扰的影响较大。     

高速数字电路PCB中串扰问题的研究与仿真

针对高速数字电路PCB中传输线间串扰的严重性,从精确分析PCB中串扰噪声的角度出发,在传统的双线耦合模型的基础上,采用了一种三线串扰耦合模型。该模型由两条攻击线和一条受害线组成,两条攻击线位于受害线的两侧,线间采取平行耦合的方式。利用信号完整性仿真软件Hyperlynx对受害线上的近端串扰噪声和远端串扰噪声进行了仿真。仿真结果表明,不同的传输模式和传输线类型、信号层与地平面的距离、耦合长度、传输线间距和信号上升/下降沿等因素会对受害线上的近端串扰和远端串扰产生较大的影响。在分析仿真结果的基础上,总结出了高速PCB设计中抑制串扰的有效措施,对高速数字电路设计有一定的指导意义。     

Finite element method applied to modeling crosstalk problems onprinted circuit boards

In modeling crosstalk on printed circuit boards, the distributed parameter transmission line model is applied to include the effects of electromagnetic coupling between tracks. Starting with a finite element approach, a computer model for predicting crosstalk voltages and currents in a general n+1 multiconductor configuration is outlined. After the currents on each track are calculated by using the finite element method and modal analysis, a simple radiation model is used to calculate the radiated field produced by the printed circuit boards for a frequency range of 30-1000 MHz. The algorithm presented was implemented in a series of Fortran programs, and the results obtained using this procedure compare very well with available theoretical and experimental data     

Calculation of the characteristics of two-wire lines in multiconductor cables

A rigorous method is proposed for calculating the parameters of two-wire lines (twisted pairs) surrounded by a single metal shield and the mutual coupling between these lines. It is shown that coupling between the lines in multiconductor cables results in electromagnetic interference (crosstalk) in communications channels and that inphase currents in the lines are caused by the asymmetry of excitation and loads. The stray voltages induced across the impedances placed at the beginning and the end of an adjacent line are determined at a given power in the main line. The effect produced by the loads placed between the wires and the shield is considered. The proposed method allows generalization of the obtained results to the case of lossy multiconductor cables.     

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.     

并行传输线共模泄漏的等效场-线耦合数值模型

针对并行传输线间感性和容性耦合计算问题,该文提出并行传输线等效场-线耦合亚网格时域有限差分(FDTD)数值模型,模型更适合非均匀介质等复杂情形的耦合串扰求解,且具有更为简洁的数值计算形式。利用该等效场-线耦合数值模型,对并行传输线间共模电磁信息泄漏进行模拟仿真和实验测试,时域模拟和频域实验结果均表明,该模型可以有效刻画并行传输线共模电磁信息泄漏发射特性。     

Analysis of crosstalk interference in CMOS integrated circuits

The authors show how crosstalk coupling between transmission lines inside CMOS integrated circuits can provoke faulty behavior by affecting the propagation delay of the logic and analog cells. A simplified model for the evaluation of parasitic capacitive coupling effects is proposed, and the influence of crosstalk on the behavior of basic functions such as logic gates, latches, RAM memory, and analog-to-digital converters is evaluated     

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.     

Simulation and modeling-simulating crosstalk and field to wirecoupling with a SPICE simulator

The simulation of two electromagnetic compatibility (EMC) problems, namely crosstalk and field-to-wire coupling, using SPICE are described. These modeling techniques for simulation of EMC of multiconductor transmission lines allow calculation in the time domain, as well as the frequency domain. Nonlinearities, protective devices, and even complex circuitry can be included at both ends of the transmission line. Disturbing voltages can also be studied at any node in a susceptor network. The techniques also offer the possibility of including arbitrary sources of radiated disturbances, which could allow the simulation of aperture coupling in an enclosure     

双阻带红外频率选择表面的设计

为实现在中、远红外两个大气窗口的低透过率,设计了一种基于六边形环状结构的双屏红外频率选择表面（FSS）,利用CST电磁软件进行仿真分析,发现该FSS在3~5 m和8~14 m两个波段内的平均透过率低于2.5%,实现了红外波段的双阻带;采用表面电流模式分析法和有效介质理论分析了该FSS的滤波机理,发现不同谐振点处由于屏间耦合或屏内单元间的耦合在谐振单元表面感应出对称分布的电流从而使散射总场增强,形成增强型反射,即比较理想的红外光阻带;最后研究了电磁波的极化方式、入射角度、介质属性以及结构参数对FSS传输特性的影响。结果表明该FSS具有良好的偏振稳定性和角度稳定性,介质属性和结构参数对其传输特性有较大影响。     

耦合传输线信道传输矩阵建模及串扰抵消效果分析

针对高速互连系统中传输线上的串扰问题,基于电磁耦合理论,研究了耦合传输线信道传输矩阵的性质,建立了以下两种情况的耦合传输线信道传输矩阵模型及其矩阵分解形式,分别是：（1）考虑受扰线两边各一条相邻微带线对受扰线的串扰;（2）考虑受扰线两边各两条相邻微带线对受扰线的串扰.给出了上述两种情况下基于耦合传输线信道传输矩阵分解形式的串扰抵消方案,并利用仿真工具ADS对其进行了验证.结果表明：信号抖动和失真大幅下降,串扰抵消效果良好,并且第二种情况下的串扰抵消效果优于第一种情况.该结果说明了在基于耦合传输线信道传输矩阵进行串扰抵消时,考虑两边各两条相邻微带线的串扰效果较好,对保持高速信号完整性具有一定的实际应用价值.     

An efficient algorithm for the calculation of parasitic couplingbetween lines in MIC's

A new algorithm is developed to calculate parasitic coupling between transmission lines in an efficient manner. The algorithm works by using the currents and voltages on the lines in the absence of parasitics to calculate independent voltage and current sources which then give the approximate coupling strength between the various lines. These sources are easy to place in a CAD circuit program. The algorithm is demonstrated on a double-stub filter structure. The observed splitting of the resonance, for this particular example, is modeled by using dependent sources, as calculated from the independent sources     

Scattering induced crosstalk in active directional couplers

Scattering from defects in an integrated optical device causes phase randomization and depolarization. Scattered light can be recaptured by the waveguides of the device and perturbs modal fields. This leads to crosstalk in directional coupler switches. A defect-scattering-induced crosstalk model is developed and crosstalk in one-, two-, and three-electrode directional couplers is investigated with the model. The number of independent electrode voltages needed to tune out crosstalk is studied. Simulations show that scattering-induced crosstalk can be tuned out completely in active directional couplers with two independent electrode voltages. When modal differential loss and unequal taper coupling are taken into account, two independent electrode voltages are insufficient to tune out the crosstalk, whereas three independent electrode voltages are sufficient. This agrees with the conclusion from previous three-electrode directional coupler experiments