FEXT cancellation for twisted-pair transmission

This paper discusses a far-end crosstalk (FEXT) canceller for twisted-pair transmission. Many twisted-pair systems such as fiber-to-the-curb, very high-speed digital subscriber line, and high-speed LAN systems, use frequency-division duplexing (FDD) for duplex transmission. It is shown that the maximum reach of FDD twisted-pair system is limited by the performance of its upstream channel, which is assumed to be located at higher frequencies than the downstream channel. In order to improve the performance of such an FDD transceiver, FEXT cancellation is introduced for the channel at higher frequencies. A system arrangement and its blind startup procedure are studied when the FEXT canceller and equalizer are jointly adapted to combat channel intersymbol interference, FEXT, and other additive noise. We investigate the initial convergence and the steady-state behavior of the proposed twisted-pair system without requiring transmission of an ideal training sequence. Measured characteristics as well as analytical model of the FEXT channel are used to estimate the time span needed for the FEXT canceller. It is also shown that the memory span for the FEXT canceller is almost independent of the channel, thus making our results useful for the twisted-pair system over all different channels     

Estimation of the transfer function of a subscriber loop by meansof a one-port scattering parameter measurement at the centraloffice

In order to qualify a subscriber loop for xDSL transmission, the channel capacity has to be estimated, which depends on the transfer function of the network. A method is provided to estimate the transfer function of the subscriber loop only measuring the one-port scattering parameter at the central office. We consider three types of networks according to their topology: a single line, a homogeneous network with a bridged tap, and a cascade of two line sections. For each type of network a parametric model is derived of its one-port scattering parameter and transfer function based on the physical line model VUB0. The model for the scattering parameter is used to identify the network based on the corresponding measurements by means of a maximum-likelihood estimator. The estimated parameters are substituted in the transfer function model, which is needed for the capacity estimation. The proposed models and estimators are validated by measurements and simulations. For the measurements, which were performed with a network analyzer, three types of twisted-pair cables were used: British Telecom (BT), Deutsch Telekom (FT), and Belgacom     

High-frequency characterization of twisted-pair cables

A wave propagation method model is proposed for the extraction of propagation parameters of high-bit rate digital subscriber twisted-pair cables. The model is derived from the scattering parameters of a transmission line. The frequency dependence and the skin effect are studied. Experimental simulations are performed to evaluate the accuracy of the extracted parameters. Good agreement is found in the cases studied     

双绞线BCI 等效替代强场电磁辐射实验研究

针对低频线缆耦合通道中最常见的双绞线电缆,以比较典型的互连线缆双绞线为研究对象,针对互连系统单端为非线性受试设备的电磁辐射敏感度进行实验研究。对连续波电磁辐射条件下双绞线传输线负载响应进行了理论推导,分析了典型互连系统辐射与注入的等效以及在高场强下的外推条件。对双绞线耦合通道大电流注入法(BCI)等效替代强场连续波电磁辐射的实验结果进行了分析,验证了BCI 等效替代强场连续波电磁辐射实验方法的准确性。     

高可靠性远程数据传输系统设计

摘要：针对数据在远距离高速传输系统中存在的可靠性低的问题,提出了一种基于LVDS长线传输和8b/10b编码的解决方案。该设计以LVDS为数据传输接口,在硬件电路上加入均衡设计,补偿长线传输的损耗;在逻辑设计上加入8b/10编码,实现传输中的直流平衡,提高数据传输的可靠性。经验证,该系统工作稳定,串行数据以400Mb/s的速率,可实现在百米双绞电缆传输线或2km光纤传输线上的零误码传输。     

155.52 Mb/s data transmission on category 5 cable plant

The authors report on the emission characteristics of category 5 cable plant in some typical situations, and offer an assessment of receiver performance and complexity, comparing the NRZ, MLT3, BPR1, and BPR4 line codes for 155 Mb/s transmission on category 5 unshielded twisted-pair cable (UTP)     

Sub-millimeter-Wave Equivalent Circuit Model for External Parasitics in Double-Finger HEMT Topologies

We present a novel distributed equivalent circuit that incorporates a three-way-coupled transmission line to accurately capture the external parasitics of double-finger high electron mobility transistor (HEMT) topologies up to 750 GHz. A six-step systematic parameter extraction procedure is used to determine the equivalent circuit elements for a representative device layout. The accuracy of the proposed approach is validated in the 90–750 GHz band through comparisons between measured data (via non-contact probing) and full-wave simulations, as well as the equivalent circuit response. Subsequently, a semi-distributed active device model is incorporated into the proposed parasitic circuit to demonstrate that the three-way-coupled transmission line model effectively predicts the adverse effect of parasitic components on the sub-mmW performance in an amplifier setting.     

基于M28945和M28927的传输单元的设计

介绍了美国敏讯(Mindspeed)公司开发的M28945与M28927芯片组的结构和特性。给出了采用该芯片组的G.SHDSL多速率传输单元的软硬件设计。该传输单元能够完成对业务信息的有线传输,可通过外部监控设置线路传输参数。芯片组参数可以用单片机或RS232调试口配置,使系统具有很强的扩展性。数字信号可以通过该系统利用双绞线进行远距离传输,传输距离可达4km。     

Predicting the Magnetic Fields from a Twisted-Pair Cable

A theory that predicts the magnitude of low-frequency magnetic fields near a current-carrying twisted-pair cable is developed. By asymptotically expressing the theoretical results, it is shown that the magnetic fields from a twisted-pair cable of pitch distance p decrease exponentially with the radial distance from the center of the cable. The asymptotically expressed result is verified experimentally for a radial distance as large as (3/2)p. At such a distance, the maximum fields from the cable are shown to be 50 dB below that from a two-wire line (two parallel wires), even though both the cable and the wire line are carrying the same amount of current.     

Performance analysis of Viterbi detection of class IV partialresponse for data transmission over multipair cables

Partial response class-IV signaling combined with Viterbi decoding to perform maximum-likelihood sequence detection is considered for high-speed data transmission over twisted-pair cables. In order to establish which data rates and distances can be achieved by this method, a performance evaluation is conducted. Binary and quaternary modulations are considered, and disturbance of the received signal by near-end and far-end crosstalk and additive white Gaussian noise is taken into account. A benchmark comparison with rigorously optimized symbol-by-symbol detection systems using AMI and HDB3 line coding is presented     

微型局域网可靠性分析

微型局域网是使用一根数据线与一根返回线实现数据通信的主从式网络。最大的特点是在一对双绞线上除了实现数据、地址、控制三种信息流的传输外,还由主机通过这对双绞线集中给各分机馈送电源。这是一种低开销的数字局域网解决方案。微型局域网是器件、电缆和线路连接的复杂组合。因此,用户有时会发现虽然系统工作在技术要求的范围内,但所建立的网络却无法工作。有时还会发现已经设计好的,并在单一阿络经过测试的一个特定总线主机对其它布局却不适用。针对上述存在的问题,本文就微型局域网中对可靠性产生影响的因素进行初步探讨。     

Joint signaling strategies for approaching the capacity oftwisted-pair channels

A technique is presented for jointly optimizing the signaling in the two directions of transmission on a twisted-pair communications channel. It is then applied to twisted-pair channel models with monotonic channel response and crosstalk transfer functions. While the signaling strategy presented in this paper can achieve only a lower bound on the true channel capacity, it is a significant improvement over existing signaling schemes. In particular, in contrast with existing schemes, the maximum information rate for the joint signaling strategy increases without bound as the signal-to-noise ratio (SNR) approaches infinity. It is also shown through numerical results that the proposed signaling strategy generalizes naturally to more practical nonmonotonic twisted-pair channel models incorporating bridge taps and other nonidealities. Finally, the form of the optimal signaling strategy suggests a relatively straightforward implementation using multicarrier modulation     

An efficient numerical approach for modeling microstrip-typeantennas

An efficient numerical approach to model antennas that include a microstrip element radiating in the presence of material layers is developed. The class of antennas considered is fed through the ground plane by a coaxial transmission line. The reaction integral equation is formulated by treating the coaxial aperture as part of the antenna. The substrate thickness can be arbitrary, making this numerical technique suitable for high-frequency applications. The effects of the substrate are also included in the analysis. Numerical results are obtained for the current distribution and input impedance. The algorithm is validated with experimental results     

A multirate transceiver IC for four-wire full-duplex datatransmission

A CMOS IC transceiver for full-duplex data transmission at 14 data rates is described. At the highest rate of 72 kb/s, two of these chips communicate on a four-wire twisted-pair telephone loop with loss at 36 kHz of up to 48 dB. The chip performs all line driving, timing recovery, and data recovery functions with only 11 passive external line interface components. The transceiver can converge on all digital data service (DDS) lines. sending and receiving unscrambled data without the need for a training sequence. The chip was fabricated in a 2-μm, double-polysilicon, double-metal process with an area of 49 mm² . Power consumption is 200 mW from the single 5-V supply     

On the frequency-dependent line admittance of VLSI interconnect lines on silicon-based semiconductor substrates

In this paper, a method for analysis and modelling of transmission interconnect lines with zero- or non-zero thickness on Si–SiO₂ substrate is presented. The analysis is based on semi-analytical expressions for the frequency-dependent transmission line admittances. The electromagnetic concept of free charge density is applied. It allows us to obtain integral equations between electric scalar potential and charge density distributions. These equations are solved by the Galerkin procedure of the method of moments. This new model represents narrow and thick line interconnect behaviour over a wide range of frequencies up to 20 GHz. The accuracy of the developed method in this work is validated by comparing with the rigorous simulation data obtained by full-wave electromagnetic solver and CAD-oriented equivalent-circuit modelling approach. The response of the proposed model is shown to be in good agreement with the frequency-dependent capacitance and conductance characteristics of general coupled multiconductor on-chip interconnects.     

A wideband crosstalk canceller for xDSL using common-mode information

This letter uses the twisted-pair common-mode signal as the input of an adaptive canceller to remove some wideband crosstalk in a digital subscriber line (xDSL) differential signal. Simulations using simple crosstalk and line balance models show the potential benefits of the canceller to improve the signal-to-noise ratio of an xDSL channel.     

双绞线及其制作综述

双绞线是综合布线工程中最常用的传输介质。网络连接电缆的质量对于保证网络的整体性能至关重要。对双绞线及其制作方法逐一进行介绍。     

On the capacity of a twisted-wire pair: Gaussian model

The performance of a twisted-pair channel is assumed to be dominated by near-end crosstalk (NEXT) from other pairs in the same cable. Both intrabuilding local and central office loop channels can be modeled as NEXT-dominated channels. The capacity of this type of channel is found, using a Gaussian model. It is shown that the capacity is independent of the transmitted power spectral density. The results also indicate that present systems operate far below theoretical capacity. The capacity of a twisted-pair channel with both NEXT and white Gaussian noise present is also addressed     

A ray-tracing approach for indoor/outdoor propagation throughwindow structures

A ray-tracing approach for indoor/outdoor propagation through windows is proposed. Using both the finite-difference time-domain (FDTD) method and a ray-tracing algorithm, several cases of indoor/outdoor propagation through windows were investigated. It is shown that wave transmission through windows cannot generally be accounted for through a single transmission coefficient parameter. Instead, a full diffraction pattern needs to be accounted for and multiple-ray representation is therefore required. It is also shown that a single window model may be used to calculate transmission through set of windows in a typical building structure as a building block. Results from the implementation of a multiple-ray representation and FDTD simulations showed good agreement. Results were validated for both normal and oblique incident cases. The developed ray-tracing approach, therefore, facilitates the use of the developed window model in available ray-tracing algorithms often used for propagation characterization of urban environments. Simulation results were further validated by conducting measurements on scaled models at 30 GHz. The experimental results agreed well with the simulation data, thus validating the accuracy of the developed ray-tracing model for transmission through windows     

建筑外窗保温性能检测装置测控系统的设计与实现

以建筑节能为目的,介绍了一种建筑外窗保温性能检测装置测控系统的设计与实现。依照现场总线的技术要求,系统硬件采用通用微型计算机为主机,各种测控仪表为从机,双绞线为传输介质,按照RS-232／RS-485串行总线标准及接口技术实现主从机之间的信息交换。讨论了在Visual C＋＋开发平台下,利用串口类CSerialPort实现多串口通信,以及多线程、数据库、打印等功能的实现。实现了根据国家标准GB／T8484-2002的要求完成的测控功能。