A Brief History of Work in Transmission Lines for EMC Applications

A brief chronology of the application of transmission line theory to electromagnetic compatibility (EMC) applications is presented. Transmission line studies in EMC began in the 1950s and 1960s with the frequency-domain analysis of crosstalk in cables. Nuclear electromagnetic pulse (EMP) concerns in the 1970s caused an increasing emphasis on the study of incident field excitation of the lines. The advent of digital technology in the 1980s moved the research emphasis toward the analysis of the transmission lines in the time domain. Early work concentrated on lossless lines whose solutions are very simple. After the 1980s, the impact of high-speed digital technology has driven much of the research toward the study of ways to incorporate line losses (particularly, frequency-dependent losses as with skin effect) into the solutions. In addition, the increasingly complex digital systems have resulted in the study of how to optimize the representation and solution of large interconnected networks of transmission lines. This paper attempts to put the historical evolution of the study of transmission lines in EMC in a chronological perspective.     

Sensitivity analysis of multiconductor transmission lines andoptimization for high-speed interconnect circuit design

Sensitivity analysis of multiconductor transmission lines is derived from a new, all-purpose multi-conductor transmission line model in both frequency domain and time domain. Computer implementation of this new model as well as the sensitivity analysis has been completed. It enables efficient, accurate simulations of interconnect circuit responses as well as sensitivity analysis with respect to both electrical and physical transmission line parameters. By applying sensitivity analysis to high-speed interconnect circuit design, design variables are optimized to achieve simultaneous minimization of crosstalk, delays and reflections at desired nodes in the circuit without violating any indispensable design rules. Numerical examples are presented to demonstrate the validity of the proposed sensitivity analysis and illustrate its application to the optimization of high-speed interconnect circuit design     

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。     

Modal technique for the time domain analysis of crosstalk betweencoaxial cables

A study of current dominant coupling in a system comprising a large number of mutually coupled braided coaxial transmission lines is presented. An efficient model for the crosstalk is developed in the frequency domain using distributed circuit parameters and the concept of transfer impedance. The lines are assumed to be lossy and to have frequency-dependent per-unit-length parameters, and further losses due to the braided nature of the outer conductors are account for in the analysis. The validity of the coupling model is tested against measurements in the frequency domain before using fast Fourier transforms to evaluate the time domain responses     

Analysis of transients in nonuniform and uniform multiconductortransmission lines

The author presents an effective method for computation of the transient response of multiple nonuniform transmission lines. This time-domain analysis technique can predict reflections and crosstalk. The proposed spectral technique is used to transform partial differential equations describing a system of transmission lines into a set of linear ordinary differential equations, which can be solved with one of the many well-developed integration techniques. Numerical experiments performed with the prototype program showed that the method can solve specific problems (lossless, uniform lines) just as fast as less general methods based on modal analysis exploiting the particular properties of lines     

Analysis and modeling of multilevel parallel and crossing interconnection lines

Analytical and numerical techniques to study the pulse propagation characteristics such as delay, distortion, and crosstalk in multilevel interconnections associated with high-speed digital IC's including VLSI chips are presented. The parallel and crossing interconnections at various levels are modeled as lossy coupled lumped distributed parameter systems, which are analyzed for their time domain characteristics. The characterizing electrical parameters of the structures are computed by utilizing the network analog method that has been formulated to solve for the lossy line constants and parasitic coupling associated with a three-dimensional multiconductor system in a layered lossy medium. It is shown that the time domain response of the multiport structures can be computed by using standard CAD programs such as SPICE by utilizing compatible circuit models developed from the solution of such systems. Examples of the step and pulse response of typical systems are included to demonstrate the versatility, usefulness, and accuracy of the techniques presented in the paper.     

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     

Characterization of picosecond pulse crosstalk between coupledmicrostrip lines with arbitrary conductor width

The propagation and crosstalk properties of picosecond electrical pulses along coupled microstrip lines with arbitrary strip widths are investigated. The current distributions and propagation constants of the dominant c- and π-modes in these asymmetric coupled striplines are calculated using the spectral domain approach; and the full-wave analysis results obtained are incorporated into a fast Fourier transform (FFT) algorithm to simulate pulse distortion and crosstalk in the coupled transmission lines. Several samples of asymmetric coupled microstrip lines are fabricated and their characteristics are measured. The results of experiments are found to be in good agreement with those of computer simulations. For the first time, rigorous results of picosecond pulse distortion and crosstalk in asymmetric coupled transmission lines are provided     

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     

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。     

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。     

Altered phase velocity lines for low crosstalk microstrip interconnection of high-speed digital circuits: design and experimental validation

Altered phase velocity lines are a novel kind of parallel microstrip lines for high-speed interconnection of digital circuits, on which the crosstalk is reduced by the different phase velocities of propagation on the adjacent lines. In this paper, a design method is proposed to optimize the geometry sizes of the altered phase velocity lines. The measured results of a prototype altered phase velocity pair designed by the proposed method are presented to validate the design method. And the effects of the process variation are simulated to analyze the robustness of the prototype in fabrication. The altered phase velocity lines outperform the symmetric parallel microstrip lines in terms of the lower far-end crosstalk (FrdCtk) and the lower dielectric loss. This technique reduces the FrdCtk in the pair of the microstrip transmission lines and does not significantly improve the near-end crosstalk. The prototype works at the speed of 2 Gbps for low crosstalk digital signal transmission, while it can transmit the high-speed clock signal at 10.5 GHz, so the altered phase velocity lines are a useful supplementary to the existing low crosstalk interconnection concepts in the scenario that the parallel microstrips have to be placed closely on printed circuit board.     

Estimation of Crosstalk in Three-Conductor Transmission Lines

A simple method for sketching the frequency response of crosstalk in three-conductor transmission lines is presented. The line is composed of three perfect conductors immersed in a lossless homogeneous medium. The method allows one to obtain a logarithmic asymptote plot (Bode plot) common to automatic control and electric circuit problems. In addition, it is shown that the maximum crosstalk may occur for frequencies where the line is electrically short. The magnitude of this maximum crosstalk can be estimated from the plot.     

Defining upstream power backoff for VDSL

Very high-speed digital subscriber line (VDSL) upstream data transmission in a distributed environment will suffer from relatively strong far-end crosstalk generated by the shorter lines in the binder. This effect can dramatically reduce the upstream capacity on longer lines. To secure the capacity on lines of all lengths, shorter lines will be required to systematically reduce their transmit power. This power reduction is known as (upstream) power backoff (PBO or UPBO). This paper reviews the problem and summarizes a number of PBO techniques and results that may not be readily available in the published literature. Next, a general formulation is presented in terms of a "reference PSD" and a method is proposed to determine the optimal value of the reference PSD. This paper is mainly based on work that was done in VDSL standardization. It is an extended version of work that was previously published     

对垂直交叉线中串扰的分析

用修正后的传输线方程对垂直的导体间的串扰进行了频域模拟，通过反傅立叶变换得到时域信号。模拟表明，虽然垂直放置可使串扰幅度大幅度降低，但交叉线中仍有较强的干扰，串扰幅度与各端接入的负载有很大关系，对干扰的原因进行分析。为了证明结果的正确性，对平行导体间的串扰用时域有限差分法和本方法进行模拟，得到一致的结果。该文对实际应用有参考价值。     

Finite Word Length Effects on Transmission Rate in Zero Forcing Linear Precoding for Multichannel DSL

Crosstalk interference is the limiting factor in transmission over copper lines. Crosstalk cancellation techniques show great potential for enabling the next leap in DSL transmission rates. An important issue when implementing crosstalk cancelation techniques in hardware is the effect of finite word length on performance. In this paper, we provide an analysis of the performance of linear zero-forcing precoders, used for crosstalk compensation, in the presence of finite word length errors. We quantify analytically the tradeoff between precoder word length and transmission rate degradation. More specifically, we prove a simple formula for the transmission-rate loss as a function of the number of bits used for precoding, the signal-to-noise ratio, and the standard line parameters. We demonstrate, through simulations on real lines, the accuracy of our estimates. Moreover, our results are stable in the presence of channel estimation errors. Lastly, we show how to use these estimates as a design tool for DSL linear crosstalk precoders. For example, we show that for standard VDSL2 precoded systems, 14 bit representation of the precoder entries results in capacity loss below 1% for lines over 300 m.      

Minimization of delay and crosstalk in high-speed VLSIinterconnects

Design optimization of time responses of high-speed VLSI interconnects modeled by distributed coupled transmission line networks is presented. The problem of simultaneous minimization of crosstalk, delay and reflection is formulated into minimax optimization. Design variables include physical/geometrical parameters of the interconnects and parameters in terminating/matching networks. A recently published simulation and sensitivity analysis technique for multiconductor transmission lines is expanded to directly address the VLSI interconnect environment. The new approach permits efficient physical/geometrical oriented interconnect design using exact gradient based minimax optimization. Examples of interconnect optimization demonstrate significant reductions of crosstalk, delay, distortion and reflection at all vital connection ports. The technique developed is an important step towards optimal design of circuit interconnects for high-speed digital computers and communication systems     

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。