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。     

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。     

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.     

防护线减小微带线间串扰的FDTD分析

随着信号转换速度日益提高,高速电路设计中的串扰问题也日趋严重。该文分析了使用防护线减小PCB微带线间串扰的效果,并运用FDTD对长耦合微带线进行了仿真验证。仿真结果表明,只要:(1) 添加有接地过孔的防护线并使过孔间距小于信号在RT/2(RT:传输信号的上升时间)时段内的传输距离;(2) 在满足线间距布线规则的前提下,将防护线适当加宽而又维持三条线(防护线和两条微带线)中两两之间的中心距不变,就能够有效减小线间的远端和近端串扰。     

基于串扰与干扰源相位同步的减小串扰研究

基于串扰信号相位改变与干扰源信号相位改变具有同步的特性,提出了一种在干扰线中点利用信号反相来减小串扰的方法。n条总线系统中,在编号为奇数(或者偶数)的传输线中点插入反相器,使每条传输线在前二分之一耦合长度和后二分之一耦合长度上获得的远端串扰信号幅度相等、相位相反,前后两部分耦合长度所产生的串扰信号经过自动叠加后,传输线上的远端串扰就会被抵消。仿真结果表明:所提出的方法能够明显抵消串扰。     

多攻击线引起的串扰时延故障的TPG

探讨了一种串扰时延最大化算法,并且利用被修改的FAN算法,生成测试矢量.对于一条敏化通路,利用被修改的FAN算法适当地激活相应的攻击线和受害线,使电路在最恶劣情况下引起最大通路时延,从而实现更有效的时延测试.利用了FAN算法的多路回退和回溯等主要特色,提高了测试生成算法的效率.实验结果表明,沿着任何临界通路传播的受害线相耦合的攻击线被适当地激活,并且可以对一定规模的电路的串扰时延故障进行测试矢量生成.     

基于Hyper Lynx的高速PCB板级仿真

随着系统时钟频率大幅攀升,保证高速电路的正常工作成为设计的首要任务。PCB板作为信号载体,高速数字信号的完整传输是其设计的重要指标。文中从电磁场理论出发,分析串扰的成因和解决方案,并利用Hyperlynx 软件对某型PCB进行全局和串扰仿真验证。通过不同端接方案仿真对比,选择最佳方案将串扰减小到合理范围。     

高速PCB中传输线串扰的研究与仿真

文章分析传输线串扰形成机理,使用Hyperlynx仿真软件构建串扰模型,分析影响近端串扰和远端串扰饱和的因素。仿真结果表明,传输线类型及耦合长度、线间距、攻击线数目、信号上升/下降时间、介质厚度、介电常数等因素对近端串扰和远端串扰均产生较大影响。最后在理论及仿真结果的基础上,总结出高速PCB设计中抑制串扰噪声的实用措施,具有一定的工程指导意义。     

高速数字系统的串扰问题分析

在高速数字电路设计中,信号完整性问题越来越突出,已经成为高速电路设计工程师不可避免的问题.串扰问题是信号完整性问题中的重要内容.分析串扰产生的机理,讨论各种影响串扰的因素,建立了两线串扰模型并采用Mentor Graphic公司的信号完整性分析软件Hyperlynx进行了仿真实验.仿真结果表明:耦合长度、线距、信号的上升时间以及介质层对两线之间的串扰都有直接影响,在仿真研究的基础上针对以上因素的影响提出减小串扰的有效措施.     

基于Hyperlynx的变电站状态监测无线节点信号完整性仿真分析

在变电站状态监测系统无线节点PCB设计过程中,由于存在高速电路,所以不可避免的会遇到信号完整信问题.借助IBIS模型和HyperLynx仿真软件对无线节点中的关键信号进行了反射和串扰的仿真研究.在未进行任何抑制措施时,反射和串扰对信号的影响较大,上冲和下冲幅值远大于200 mV,串扰幅值最大为370 mV.通过串联端接和加大传输线间距、减小耦合长度,反射和串扰对信号的影响明显减小,满足了信号完整性要求.     

Modelling of coupled interconnect lines for integrated circuits

A coupled interconnect model is developed using even mode and odd mode capacitance analysis. Signal coupling is presented in terms of interconnect width, substrate thickness, interconnect line spacing, and frequency. Picosecond photoconductor based measurements of coupled transmission lines on the integrated circuit support the even and odd mode signal transmission simulation results. SPICE circuit simulation is used to demonstrate the model utility and explore the sensitivity of the self- and mutual capacitances and inductances in signal crosstalk.     

非平行微带线间的串扰抵消研究

非平行微带线是印刷电路板(PCB)上不可避免的互连结构。针对PCB 上非平行微带线间的串扰问题,用平行微带线近似非平行微带线,把平行耦合微带线间的串扰抵消方法应用到非平行耦合微带线中,提出了利用耦合传输线信道传输矩阵方法来进行远端串扰抵消,在对非平行耦合传输线信道传输矩阵进行特征值分解的基础上构建串扰抵消电路。仿真了非平行微带线间夹角分别为q=3°、5°、10°时的串扰,结果表明,该方法可以有效改善非平行微带线上信号眼图的质量,串扰抵消效果良好。     

Analytical and Experimental Study on Suppression of Electromagnetic Interference on High Speed Printed Circuit Board for Wireless Communication Systems

In this paper, a novel routing topology is proposed to reduce crosstalk between parallel links used for high data rate application. Generally, microstrip lines are used in high frequency RF printed circuit boards for propagating high speed signals in wireless communication. Since RF front end modules in wireless system supports a wide ultra wide band frequency range from 700 MHz to 12 GHz, package density parasitic effects have been a major issue which degrades system performance. The close proximity of signal transmission lines with a high packing density results signal integrity problems such as crosstalk and timing jitter. A modified coupled microstrip line is proposed to reduce crosstalk by means of increasing capacitive coupling ratio. Our proposed structure reduced far end crosstalk by 4 dB and near end crosstalk by 4 dB than existing structures. The proposed microstrip line increased the maximum data rate from 1 to 3.3 Gb/s and reduced timing jitter by 51 ps at 3.3 Gb/s.     

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     

Analytical models and algorithms for the efficient signal integrity verification of inductance-effect-prominent multicoupled VLSI circuit interconnects

Novel signal integrity verification models and algorithms for inductance-effect- prominent RLC interconnect lines are developed by using a traveling-wave-based waveform approximation (TWA) technique. The multicoupled line responses are decoupled into the eigenmodes of the system in order to exploit the TWA technique. Then, the response signals are mathematically represented by the linear combination of each eigenmode response based on TWA, followed by reporting the signal integrity models and algorithms for the multicoupled lines. The signal integrity of VLSI circuit interconnects is complicatedly correlated with input signal switching-patterns, layout geometry, and termination conditions. It is shown that the technique can be efficiently employed for complicated multicoupled interconnect lines with various termination conditions and the signal transients based on the technique have excellent agreement with SPICE simulations. Thus, with the proposed technique, the switching-dependent signal delay, crosstalk, ringing, and glitches of the inductance-effect-prominent RLC interconnect lines can be accurately as well as efficiently determined.     

Crosstalk between microstrip transmission lines

Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk     

A termination scheme for high-speed pulse propagation on a systemof tightly coupled coplanar strips

A realistic termination scheme is proposed for closely coupled N-conductor microstrips. The design aims to achieve satisfactorily low signal reflection and good fabrication feasibility for the planar MMIC (Monolithic Microwave Integrated Circuit) process. The matched termination network (MTN) for a lossless three-line coupled microstrip structure is presented. High-speed pulse transmission along terminated tightly coupled microstrip lines is analyzed using modal analysis in the frequency domain. Theoretical results for the propagating and reflected waveforms are obtained by applying the inverse discrete Fourier transform (IDFT) to the system responses. These responses are obtained by applying the theory of multiconductor transmission lines to a dispersive database which has been computed using the spectral-domain approach (SDA). The response of a six-line closely coupled microstrip circuit terminated by the proposed termination scheme is measured using the HP8510B network analyzer. The measured results show that the reflected signal is below -30 dB and the results are in good agreement with the theoretical waveforms     

Dynamic Power Model of CMOS Gates Driving Transmission Lines Based on Fourier Analysis

This paper presents an analytical dynamic power model of CMOS gates driving transmission lines with distributed RLC parameters. It is shown that at high signal frequency, where the output voltage at the termination of a transmission line may not reach the steady state during a signal period, the charge and voltage at the end of the period become the initial conditions of the following periods and have a significant effect on dynamic power consumption. The proposed model takes these initial conditions into account, since it is based on Fourier series analysis. In this model, the dynamic power consumption is approximated by the summation of the first several Fourier-series-based terms. The accuracy of the model increases with the number of series terms, and arbitrary accuracy can be obtained by including appropriate number of the terms in the model. The model is much faster than simulation program with integrated circuit emphasis (SPICE), and its computational complexity is linear with the number of terms included. The model is also extended to CMOS gates driving distributed RLC trees and coupled multiconductor transmission lines.