“单端—差分”微带线串扰仿真分析

运用电磁场仿真软件分析"单端-差分"微带线结构的串扰问题。结果表明:增加单端干扰线和被干扰差分对的间距,可以同时减弱差分对的近端串扰和远端串扰;单端线和差分对间添加防护线可大幅减少远端串扰,且近、远端串扰均低于40 dB;改变防护线与单端干扰线及被干扰差分对的间距,差分对的近、远端串扰变化不大。     

平行差分线对间的串扰分析

在高速互连电子设备中,模块之间大多采用差分走线来进行信号传输。然而,不同差分线对之间的串扰会影响到电路性能。本文提出采用多导体传输线理论(MTL)分析差分线对间的串扰,推导了串扰的具体表达式,并结合实际的差分线对模型,将理论分析与CST PCB STUDIO仿真结果进行对比,验证了MTL理论应用于差分线对串扰分析的有效性。     

防护线对“单端-差分”微带线结构串扰的影响

分析了使用防护线减小"单端-差分"微带线结构串扰的方法,并运用Ansoft Designer进行仿真分析,设计了两端开路、两端端接匹配电阻、两端接地、分布多个短路过孔等4种不同类型的防护线。仿真结果表明:防护线两端开路在受扰线上产生的串扰是最大的,防护线上每隔λ/10处加入接地过孔,可以非常有效地减小线间串扰。     

高密度封装中互连结构差分串扰建模与分析

针对传统模型存在较大分析误差的问题,提出高密度封装中互连结构差分串扰建模与分析.在对互连结构差分传输线耦合关系分析的基础上,建立了四线差分结构串扰模型.运用该模型对互连结构差分串扰中的电阻、电容以及电感进行等效分析,解决高密度封装中互连结构差分串扰问题.经试验证明,此次建立模型平均误差为0.042,满足抑制高密度封装中...     

基于高频高速PCB应用的新型差分线结构

本文通过分析高频高速PCB上串扰产生的机理,以两条传输线之间的耦合电容和耦合电感等作为优化的参量,提出了一种改善信号串扰的差分线结构———T型差分传输线,采用正交实验方法研究 T型差分传输线结构的多个参数对远端串扰的影响,得出了改善信号远端串扰的最优组合方案,确定了这些参数对改善串扰的重要程度及主次顺序,利用HFSS对T型差分传输线和Tabbed Line进行仿真对比分析,仿真结果表明 T型差分传输线改善串扰的效果明显优于Tabbed Line。     

防护布线的结构对PCB板级差分对之间串扰的影响

差分传输线具有低辐射和抑制共模噪声的优势,得到了越来越广泛的应用。但是传统的差分线结构不能有效的降低邻近差分对之间的串扰噪声,这将影响到高速系统的信号完整性。文中针对使用防护布线的方法,讨论了三种不同结构的防护砸线,从场的角度对比了它们的电磁屏蔽效果,利用混模S参数分析了它们对于减小串扰噪声的作用。     

PCB板级双绞互连结构减小感性和容性串扰噪声

非屏蔽双绞线已经被广泛的运用于网络的互联中,双绞的结构能够提高对串扰和辐射发射的抵抗能力。在高速数字电路的PCB板上差分信号变得越来越多。随着上升时间的加快,差分信号的信号完整性问题变得越来越重要。最近,一种新的双绞差分传输线被引入到布线中。文章通过理论和仿真分析了这种双绞差分线结构如何减小串扰和辐射发射。     

使用双绞差分结构减小印刷电路板上的串扰和辐射发射

随着发展的需要,高速数字电路PCB板上信号速度越来越快,由于差分信号有较强的抗干扰能力,因此用的得越来越普遍。但是,随着上升时间的进一步减小,差分信号的信号完整性问题也变得越来越重要。由于双绞的结构在一定程度上使得干扰相互抵消,从而提高系统对串扰和辐射发射的抵抗能力,因此,近两年来有一种新的双绞差分传输线被引入到布线中。本文从理论上分析了双绞差分线结构减小串扰和辐射发射的机理,并且通过建模仿真验证了其正确性．     

IC中多余物缺陷对信号串扰的定量研究

该文研究了铜互连线中的多余物缺陷对两根相邻的互连线间信号的串扰,提出了互连线之间的多余物缺陷和互连线之间的互容、互感模型,用于定量的计算缺陷对串扰的影响。提出了把缺陷部分单独看作一段RLC电路模型,通过提出的模型研究了不同互连线参数条件下的信号串扰,主要研究了铜互连线的远端串扰和近端串扰,论文最后提出了一些改进串扰的建议。实验结果证明该文提出的信号串扰模型可用于实际的电路设计中,能够对设计人员设计满足串扰要求的电路提供指导。     

使用防护布线减小差分传输线间的高频串扰噪声

随着高速电路的不断发展,差分传输线得到了越来越广泛的应用。它具有低辐射和较好的抗共模噪声能力。但是传统的差分线结构不能有效的降低邻近差分对之间的串扰噪声,这将影响到高速系统的信号完整性。文章针对使用防护布线的方法,讨论了三种不同结构的防护布线,在全波电磁仿真软件HFSS中建立了三维物理模型,利用混模S参数分析了它们对于减小串扰噪声的作用,从场的角度对比了它们的电磁屏蔽效果,并对如何使用防护布线提出了一些建议。     

On The Problem of Using Guard Traces for High Frequency Differential Lines Crosstalk Reduction

In this paper, the problem of using guard traces for reducing crosstalk between differential transmission line pairs is investigated, both experimentally and by full-wave electromagnetic (EM) simulations. Different cases of differential lines crosstalk are treated with and without guard trace separation between the differential line pairs. Coated microstrip printed circuit board test structures including thru-reflect-line calibration standards are designed and fabricated on a high frequency laminate material, allowing direct measurement of crosstalk between adjacent differential line pairs in the absence and in the presence of guard traces stitched with vias of regular spacing. The test structures are characterized with mixed-mode scattering parameters using a physical layer test system. Different configurations (of differential line pairs) without guard trace, with floating guard traces (which are terminated and nonterminated) and with a solid guard trace separation are investigated using a High Frequency Structure Simulator (a commercial full-wave 3-D EM simulation tool). The experimental data are compared with the simulation results, and some conclusions and guidelines on the effect of guard traces for alleviating crosstalk between differential transmission lines are presented     

Twisted differential line structure on high-speed printed circuit boards to reduce crosstalk and radiated emission

Differential signaling has become a popular choice for high-speed digital interconnection schemes on printed circuit boards (PCBs), offering superior immunity to crosstalk and external noise. However, conventional differential lines on PCBs still have unsolved problems, such as crosstalk and radiated emission. When more than two differential pairs run in parallel, a line is coupled to the line adjacent to it because all the lines are parallel in a fixed order. Accordingly, the two lines that constitute a differential pair are subject to the differential-mode crosstalk that cannot be canceled out by virtue of the differential signaling. To overcome this, we propose a twisted differential line (TDL) structure on a high-speed multilayer PCB by using a concept similar to a twisted pair in a cable interconnection. It has been successfully demonstrated by measurement and simulation that the TDL is subject to much lower crosstalk and achieves a 13-dB suppression of radiated emission, even when supporting a 3-Gb/s data rate.     

Optimal Positions of Twists in Global On-Chip Differential Interconnects

Crosstalk limits the achievable data rate of global on-chip interconnects on large CMOS ICs. This is especially the case, if low-swing signaling is used to reduce power consumption. Differential interconnects provide a solution for most crosstalk and noise sources, but not for neighbor-to-neighbor crosstalk in a data bus. This neighbor-to-neighbor crosstalk can be reduced with twists in the differential interconnect pairs. To reduce via resistance and metal layer use, we use as few twists as possible by placing only one twist in every even interconnect pair and only two twists in every odd interconnect pair. Analysis shows that there are optimal positions for the twists, which depend on the termination impedances of the interconnects. Theory and measurements on a 10-mm-long bus in 0.13-mum CMOS show that only one twist at 50% of the even interconnect pairs, two twists at 30% and 70% of the odd interconnect pairs, and both a low-ohmic source and a low-ohmic load impedance are very effective in mitigating the crosstalk     

Broad Signal Constraints for the Management of the Spectrum in Telephone Loop Cables: Identical Constraint on All Pairs

A previous paper showed that constraining the total energy transmitted on all pairs in a cable during any time interval of a specified duration limits the maximum instantaneous near-end crosstalk voltage on any pair. This paper determines a constraint on the energy that is the same for each pair and that guarantees the same limit on near-end crosstalk. While the new constraint permits less variation of transmitted power among the pairs, it permits greater average power per pair. Thus, the constraint developed herein would be particularly useful when a cable is used principally for one type of capability, e.g., ISDN basic access.     

Multichannel signal processing for data communications in thepresence of crosstalk

Transceiver designs for multiple coupled channels typically treat the crosstalk between adjacent twisted pairs as random noise uncorrelated with the transmitted signal. The authors propose a transmitter/receiver pair that compensates for crosstalk by treating an entire bundle of twisted pairs as a single multi-input/multi-output channel with a (slowly varying) matrix transfer function. The proposed transceiver uses multichannel adaptive FIR filters to cancel near- and far-end crosstalk, and to pre- and postprocess the input/output of the channel. Linear pre- and postprocessors that minimize mean squared error between the received and transmitted signal in the presence of both near- and far-end crosstalk are derived. The performance of an adaptive near-end crosstalk canceller using the stochastic gradient (least-mean-square) transversal algorithm is illustrated by numerical simulation. Plots of mean squared error versus time and eye diagrams are presented, assuming a standard transmission line model for the channel. A signal design algorithm that maps a vector input bit stream to a stream of channel symbol vectors is also presented and illustrated explicitly for s simple model of two coupled channels     

On-chip crosstalk mitigation for densely packed differential striplines using via fence enclosures

The measured crosstalk characteristics for close-packed via fence enclosed differential stripline structures in a standard digital CMOS process are reported. The transmission lines achieve a packing pitch of 16 /spl mu/m of interconnect width per differential pair. The nearest neighbour far-end differential crosstalk is measured to be better than -43 dB and the near-end differential crosstalk is better than -37 dB below the drive signal at frequencies up to 20 GHz for 600 /spl mu/m lines. This is sufficient for use in high-density, high-speed analogue and digital integrated circuits.     

Prediction of Crosstalk Involving Twisted Pairs of Wires-Part II: A Simplified Low-Frequency Prediction Model

In a companion paper [1],a transmission-line simulation model for predicting crosstalk involving twisted-wire pairs was developed. In this paper, a simplified model valid for low frequencies is developed. The total coupling is separated into inductive and capacitive coupling contributions. The capacitive coupling contribution is shown to provide a "floor" which limits the effect of reducing the inductive coupling achieved by twisting a wire pair for the unbalanced case and is zero for the balanced case.     

A frequency-domain approach to crosstalk identification in xDSLsystems

Crosstalk between multiple services transmitting through the same telephone cable is the primary limitation to digital subscriber line services. From a spectrum management point of view, it is important to have an accurate map of all the services that generate crosstalk into a given pair. If crosstalk is measured via modem-based methods, i.e., while a digital subscriber line (DSL) system is running, what is measured is the crosstalk in the bandwidth of the considered DSL system. For this reason, DSL services running on adjacent pairs may not be detected if their bandwidth is not significantly overlapping with the bandwidth of the disturbed system. This is a major drawback of modem-based system identification techniques since, from a spectrum management point of view, it is important to be able to identify all crosstalkers. We address the important problem of crosstalk identification when the pair under test does not bear DSL services, i.e., via a non-modem-based approach. Crosstalk sources are identified in the frequency domain by finding the maximum correlation with a “basis set” of representative measured crosstalk couplings. The effectiveness of the proposed technique is also verified on the basis of real crosstalk measurements performed on actual cables. Finally, new techniques based on multiple regression and best basis selection are also discussed