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1、眼图及眼图在串行信号测试中的运用,DM高级应用工程师:黄腾Email:,2023/8/21,V1.0 Confidential,2,眼图分析的原始驱动,通讯技术发展的需要 SONET和SDH的在广域传输中的广泛应用以及以太网技术的爆炸式应用和发展电子系统从传统的并行总线转为串行总线 Highly Scable,Serial Interface 采用当前许多最新的通讯行业成熟应用的技术:Point to Point Interconect,Switch-based Technology,Packetlized Protocol,2023/8/21,V1.0 Confidential,3,高速串行
2、总线和传统并行总线对比,2023/8/21,V1.0 Confidential,4,高速串行总线新兴标准和数据速率,2023/8/21,V1.0 Confidential,5,眼图定义,2023/8/21,V1.0 Confidential,6,一般信号与眼图的区别,2023/8/21,V1.0 Confidential,7,眼图特征定义,2023/8/21,V1.0 Confidential,8,眼图特征定义,2023/8/21,V1.0 Confidential,9,眼图形成示意,2023/8/21,V1.0 Confidential,10,眼图在示波器上的形成,2023/8/21,V1.
3、0 Confidential,11,眼图的CLK,采样示波器的CLK通常可能是用户提供的时钟,恢复时钟,或者与数据信号本身同步的码同步信号.实时示波器通过一次触发完成所有数据的采样,不需附加的同步信号和触发信号.通常通过软件PLL方法恢复时钟.Tektronix RT-Eye软件即使用此方法.,TDS8200 ET Scope(20GHz 80E03),TDS6154C RT w.DSP,2023/8/21,V1.0 Confidential,12,眼图与CLK时钟速率提高,眼图质量下降,125M CLK,250M CLK,500M CLK,2023/8/21,V1.0 Confidentia
4、l,13,示波器上的眼图,提供串行总线数据的丰富信息:通过比较发送端和接收端的眼图质量可以分析出信号传输的问题 眼高,眼底,眼宽 上升时间 下降时间 模板测试,2023/8/21,V1.0 Confidential,14,眼图与系统速率,水平时域上关联因素 Transition(rise)time Aperture time,Timing uncertainty,skew and jitter,垂直域 幅度损耗和噪声,Unimpared bit edge,2023/8/21,V1.0 Confidential,15,眼图和传输质量,Larger eye opening means greate
5、r tolerance to amplitude and timing variationsLarger eye opening translates to simpler system design and better reliabilityWider transition region indicates greater jitter and higher bit error rateBest error rate obtained when decision point is near center of the eye,2023/8/21,V1.0 Confidential,16,P
6、 Values,PTopmean,the mean value of PTopPTopsigma,the standard dev of PTopPBasemean,mean value within aperturePBasesigma,std dev of PBase in aperturePcrossmean,vertical mean of crossing pt.,T Values,Tcrossmean,horiz mean of crossing pt.Tcrosssigma,horiz std dev of crossing pt.Tcrosspk-pk,horiz pk-pk
7、of crossing pt.,The Eye Aperture defaults to the center 20%of the interval from TCross1 to TCross2 but is settable from 0 to 100%,眼图测量特征量,2023/8/21,V1.0 Confidential,17,Jitter RMS=TCross1sigma Jitter Pk-Pk=TCross1pk-pk Extinction Ratio=PTopmean/PBasemean(ER also in dB and%)Quality Factor=(PTopmean-P
8、Basemean)/(PTopsigma+PBasesigma)Eye Height=(PTopmean-3*PTopsigma)-(PBasemean+3*PBasesigma)Eye Width=(TCross2mean-3*TCross2sigma)-(TCross1mean+3*TCross1sigma)Crossing Percent,Duty Cycle Distortion,Noisepk-pk,NoiseRMS,SNR,眼图测量特征量,2023/8/21,V1.0 Confidential,18,眼图的测量,远端,采样点,串扰 随机抖动 确定性抖动码间干扰(ISI)占空比失真(
9、DCD)正弦抖动(SJ)无关联的 幅度损耗,2023/8/21,V1.0 Confidential,19,串行总线:Basic blocks,Transmitters,Interconnects(paths),Receivers,Differential Transmitter,Dual-coax differential cable,Twisted-pair differential cable,Coupled-pair traces on circuit board(backplanes),Differential Receiver,2023/8/21,V1.0 Confidential,
10、20,高速串行总线信号线上不仅包含数据信息还包含时钟信息,path,Differential serial data is sent without any clock signal across the interconnect to the receiver,A clock is“recovered”from the incoming data at the receiver through a clock and data recovery circuit(CDR).,2023/8/21,V1.0 Confidential,21,高速串行总线数据传输过程中干扰因素增多,Transitio
11、n points often involve combinations of solder joints,circuit board vias,and connectors:these all can have substantial effect on the total link performance.,2023/8/21,V1.0 Confidential,22,高速串行总线损耗 速率越高互连距离越长,损耗越大,Reference Maxim Note HFDN-27.0(Rev.0,09/03),Clean,open,logical 1&0 at launch from transm
12、itter,Smeared edges at end of long interconnect.,Logical 1(this is often called a“closed eye”),Fast,sharp,edges at transmitter launch,2023/8/21,V1.0 Confidential,23,高速串行总线串扰,Serial data can be a single differential signal,but generally there are multiple“lanes”of serial data running side by side;the
13、se can CROSSTALK with each other.,2023/8/21,V1.0 Confidential,24,高速串行总线精度 设计者要更加精确的掌控设计,6.25Gb/s at Tx launch into backplane,6.25Gb/s at 17in(43cm)of backplane,6.25Gb/s after 34in(86cm)of backplane,Small differences in levels being measured,2023/8/21,V1.0 Confidential,25,如何获得张开的眼图,走线长度 短走线并非始终能够满足.短
14、走线意味低损耗.走线宽度 宽走线可以降低趋肤效应.减小板材的介电常数 即降低介电损耗(Dielectric Loss),但将增加成本.信号预加重和均衡处理 通过对跳变位预加重(Pre-Emphasis)处理补偿线路上因信号跳变产生的针对高频分量的损耗.其它接收端均衡处理等.,2023/8/21,V1.0 Confidential,26,眼图与BER,究竟这个眼睛有多开?(这却与你观察多久有关),?,2023/8/21,V1.0 Confidential,27,眼图与BER,pdf 1,pdf 2,cdf 2,0.5UI,1,2,A,B,C,0UI,1UI,Eye open for BER 1.
15、0E-12,-0.5UI,1.5UI,cdf 1,1,1,0,眼睛睁开度 vs 误码率,2023/8/21,V1.0 Confidential,28,眼图与BER,利用眼图分析抖动得到浴盆曲线(Bath Tub),从而进行误码率的估算。,2023/8/21,V1.0 Confidential,29,泰克提供的眼图测量方案,从数据恢复时钟(CDR),眼图模板测试硬件 CDR(PLL)软件 CDR(PLL+其它)测量绘图抖动:趋势,频谱,直方图,浴盆曲线,2023/8/21,V1.0 Confidential,30,硬件时钟恢复,TDS6000B 系列,TDS7704B 和 CSA7404B,显示
16、器,锗化硅触发 系统,放大器/衰减器,数据采集系统,Golden PLL,来自被 选中的通道,恢复时钟,Ch2,Ch3,Ch4,从1Mbit/s到 3.125Gbit/s的所有电接口和光接口速率,独有的 锗化硅触发系统,2023/8/21,V1.0 Confidential,31,硬件时钟恢复产生的眼图,TDS6804B/P7380SMADSP增强功能XAUI 超过 3.125Gb/s眼图测量和统计,2023/8/21,V1.0 Confidential,32,新型测试方法RT-Eye方法生成眼图,新兴标准要求新型工具TDS RT-Eye(选项RTE)基于泰克在软件领域的专家经验，创建了一个交
17、钥匙式的一致性测试和分析解决方案,2023/8/21,V1.0 Confidential,33,新型测试方法RT-Eye方法生成眼图,软件时钟恢复眼图全系列标准专用参数测量，包括幅度、定时和抖动多种格线图，进行补充数据分析标准专用模块作为插件提供用户可定制的波形模板、测量极限和报告功能，支持专有标准和新兴标准生成报告,2023/8/21,V1.0 Confidential,34,新型测试方法RT-Eye方法生成眼图,低抖动本底噪声在TDS6604 或 TDS7704B上为700 fs RMS单触发事件，而不是ET方法中的多触发事件支持不同的时钟恢复模型锁相环(PLL)相位内插重复取样(恒定时钟
18、,连续位)数据相关分析把跳变位与非跳变位分开码型长度检测，进行抖动分析(Rj/Dj分离)恢复高达 10Gb/s 的时钟高达 5Gb/s 的眼图高达 10Gb/s 的抖动分析0.1 UI的抖动本底噪声,2023/8/21,V1.0 Confidential,35,RT-Eye眼图示例TDS6804B和下一代标准,2.5Gb/s5Gb/s6.25Gb/s,2023/8/21,V1.0 Confidential,36,新型测试方法RT-Eye方法生成眼图分析结果,2023/8/21,V1.0 Confidential,37,新型测试方法RT-Eye方法生成眼图抖动一致性测量,T TX-EYE-MED
19、IAN-to-MAX-JITTER,TTX-EYE-MEDIAN-MAX-JITTER,2023/8/21,V1.0 Confidential,38,新型测试方法RT-Eye方法生成眼图抖动一致性测量,抖动眼图张开+总抖动=1UI,2023/8/21,V1.0 Confidential,39,采样示波器眼图生成,When a clock signal is used to trigger the equivalent-time 8200 scope the sampled DATA signals generally create EYE PATTERNS(between clock trig
20、gers the sampled DATA could be either a logical 1 or 0),Data,trigger,voltage,time,Precision variable delay,A clock trigger can be user-supplied or recovered from the data to trigger the equivalent time sampler,Clock,Eye patterns are the common result of clock-triggering in Equivalent time sampling:v
21、ectors are not drawn since adjacent samples can jump from logical 1 to 0 frequently,2023/8/21,V1.0 Confidential,40,CSA8200 with 20GHz 80E03,采样示波器比较DRT示波器有更好的信号保真度,A fast,step.,DSP ON,tR 10-90=22psaberrPkPk=0%,6.1%,tR 10-90=30.3psaberrPkPk=9.5%,7.2%,TDS6154C,DSP On.,Averaging on,2023/8/21,V1.0 Confid
22、ential,41,CSA8200 with 20GHz 80E03,采样示波器比较DRT示波器有更好的信号保真度,A fast,step.,TDS6154C,DSP On.,DSP ON,tR 10-90=21psaberrPkPk=0%,5.5%,tR 10-90=22.5psaberrPkPk=10.4%,11.3%,Averaging off,2023/8/21,V1.0 Confidential,42,TDS8200 ET Scope(20GHz 80E03),采样示波器与DRT示波器眼图对比,TDS6154C RT w.DSP,An Advantest 12Gb BERT(D318
23、6)was used to differentially drive two channels and also supplied a reference clock.LEFT:CHA-CHB on an TDS8200 with 80E03 20GHz sampler and an 82A04 Phase Reference moduleRIGHT:CH2-CH3 on a TDS6154A(TDS6154C)realtime scope;eye generated using RT-Eye.,2023/8/21,V1.0 Confidential,43,TDS8200 ET 80E04,采
24、样示波器与DRT示波器眼图对比,TDS6154C RTO,DSP On,Slow Eye Diagram(4GFC,cca.80ps edges,600mV full swing)(TDS6154 comparison is a composition),Mask Margin=80%,Mask Margin=47%,Mask_MarginCSA is about 1.7x Mask_MarginTDS,2023/8/21,V1.0 Confidential,44,应用对比选择,TDS6154CDebugTriggeringProbingSignal AcquisitionSingle sho
25、t capableNon-repetitive signalsSuperior Advanced AnalysisJitterSerial Data ApplicationsPower,etc.,TDS8200Signal FidelityBandwidthNoiseAberrationsVertical&Horizontal resolutionTDR&TDR probingFuture Extendibility(Modular)Optical Support,2023/8/21,V1.0 Confidential,45,Your Turn,Questions?Concerns?Sugge
26、stions?,Thank You For Attending!,Mobile Phone:(0)13761684620,2023/8/21,V1.0 Confidential,47,光通信基础知识介绍-性能参数,光通信眼图比较关注的性能参数 OMA(Optic Modulation Amplitude)和ER(Extinction Ratio)Q(Quality)OSNR(Optic Signal to Noise Ratio)Eye Opening/Eye Opening Penalty Bit Error Rate Reciver Sensitivity,2023/8/21,V1.0 C
27、onfidential,48,光通信基础知识介绍-性能参数,逻辑1和逻辑0:光功率高的状态是逻辑1，反之则为逻辑0.光功率常用:dBm=10log10(Power(mW)/1(mW)OMA:Optical Modulation Amplitude 逻辑1和逻辑0光功率差:OMA=P1-P0 有时也定义成:ER:Extinction Ratio,消光比,2023/8/21,V1.0 Confidential,49,光通信基础知识介绍-性能参数,另外一个重要术语就是Q.理论上系统的误码率BER是完全由光纤的信噪(Signal-to-Noise Ratio)比决定的,也就是Q.一般主要在光纤放大器和
28、接收端进行测量.,2023/8/21,V1.0 Confidential,50,光通信基础知识介绍-性能参数,OSNR:Optical Singal-to-Noise Ratio 对RZ编码传输系统,亦可定义如下:和 定义如右图示EOP:Eye Opening Penalty 测量系统的垂直方向的眼图 张开度,公式定义如下:,2023/8/21,V1.0 Confidential,51,光通信基础知识介绍-性能参数,BER:Bit Error Rate 与Q和OSNR或光功率相关,是衡量传输系统性能的最直观的特征.,当前光通信系统要求的BER一般在1E-9到1E-12之间.,2023/8/21
29、,V1.0 Confidential,52,光通信基础知识介绍-SDH/SONET,SONET:Synchronous Optical Network.北美标准.SDH:Synchronous Digtial Hierarchy.欧洲标准.中国采用SDH标准.,2023/8/21,V1.0 Confidential,53,光通信基础知识介绍-SDH/SONET,2023/8/21,V1.0 Confidential,54,光通信基础知识介绍-SDH/SONET-光速率,2023/8/21,V1.0 Confidential,55,光通信基础知识介绍-SDH/SONET 眼图模板,Rates,X
30、1,X2,Y1,STM-1OC-1&OC-3,STM-4OC-9 to OC-24,0.15,0.35,0.20,0.25,0.40,0.20,STM-1,STM-4,OC-1 to OC-24,NormalizedAmplitude,Time(UI),1+Y1,1-Y1,1,0.5,Y1,0,-Y1,2023/8/21,V1.0 Confidential,56,光通信基础知识介绍-SDH/SONET-Transmit Power Levels,2023/8/21,V1.0 Confidential,57,光通信基础知识介绍-SDH/SONET-Measuring Transmit Power
31、,Oscilloscope with OE ConverterLimited Dynamic Range(0 to-35 dBm)Accuracy adequate for some tests(error 6%,about 0.25dB)Useful for troubleshooting functionalityOptical Power MeterExtremely wide Dynamic Range(+10 dBm to-80 dBm)Very accurate(error 3%,about 0.1 dB)Calibrated for multiple wavelengthsUse
32、ful for device calibration and accurately setting power levels,2023/8/21,V1.0 Confidential,58,光通信基础知识介绍-SDH/SONET-测试连接图,Pattern Generator,Optical Switch,Optical Power Meter,O/EReference Receiver Oscilloscope,Apparatus:Transmitter Evaluation,Data Out,Clock Out,Trigger In,S,DUT,2023/8/21,V1.0 Confiden
33、tial,59,光通信基础知识介绍-SDH/SONET Extinction Ratios,2023/8/21,V1.0 Confidential,60,Optical Bandwidth(unfiltered),CSA7404B,Electrical Bandwidth,Maximum Real-time Sample Rate,Telecom/Datacom Bit Rates(max,filtered),Optical Sensitivity,Wavelength Range,Base Price(USD),2.4 GHz,4 GHz,20 GS/s,2.5 Gb/s,-17 dBm,7
34、00-1650 nm,$63,250(AP504 CN Price),光通信测量-CSA7000B,2023/8/21,V1.0 Confidential,61,光通信测量-CSA7000B,主要产品有CSA7154B,CSA7404B.目前支持的最高速率为2.5Gb/s.,2023/8/21,V1.0 Confidential,62,光通信测量-CSA7000B-ORR,2023/8/21,V1.0 Confidential,63,光通信测量-CSA7000B-ORR,四阶Bessel-Thomson Filter 频响图,CSA7000B内嵌四阶Bessel-Thomson 数字滤波器.可
35、以保证用户在不同速率之间平滑切换.而无需更换模块进行不同速率信号的测量.,2023/8/21,V1.0 Confidential,64,光通信测量-CSA7000B-ORR,对NRZ编码光通信系统即通常的10Gb/s以下低速系统在接收端通常被设计成忽略高频上的细节,因为在高频上没有描述信号的重要参数.为了保持和真实接收端的一致性,内嵌的ORR带宽为0.75倍Bit Rate即1.5倍Bit Frequency.对RZ编码而言,Bit Frequency等于Bit Rate,则根本没有ORR标准.甚至无法确定应该在什么频率上进行滤波,虽然看起来象应该高于Bit Frequency.这是由RZ编码
36、的特点决定的.,2023/8/21,V1.0 Confidential,65,光通信测量-CSA7000B-Optical/Electrical System(ORR),WaveformMemory,2023/8/21,V1.0 Confidential,66,光通信测量-CSA7000B-Digital Filters-in the Optical Reference Receiver,2023/8/21,V1.0 Confidential,67,光通信测量-CSA7000B-ORR Performance and Simplicity,Integrated Optical Referenc
37、e Receiver(ORR)Broad-wavelength,multimode O/E700 to 1650 nm,calibrated at 780,850,1310,1550 nmLibrary of ORR Digital Filters4th-Order Bessel-Thompson filtersEasily disabled to provide full-bandwidth analysis on optical signals.Eliminates the need for reconfiguring external accessories,modules or plu
38、g-insAllows easy optical/electrical Conformance Testing on a wide range of Comm standards up to 2.5 Gb/s with one instrumentInternal calibration ensures the accuracy and repeatability of results=confidence in measurements and design margins,2023/8/21,V1.0 Confidential,68,一个典型的SONET/SDH光纤传输系统收发单元示意图.
39、The receivers output interface provides regenerated data in a serialor parallel(deserialized)bit stream,along with the recovered clock.,光通信测量-CSA7000B-Clock Recovery,在系统没有主时钟有效分布时需要采用Clock Recovery.系统主时钟可以在研究室或机房等有效分配或布置.分布式系统时钟(不同地点)可以用GPS接收机或时间-码产生机(time-code generators)进行同步(网络同步)称为1层时钟(Stratum 1
40、clocks)(highest level accuracy,synchronization).Clock Recovery提供相对精度低点,低级别的同步(抖动,PLL 相关).,2023/8/21,V1.0 Confidential,69,光通信测量-CSA7000B-Clock Recovery,Clock and Data Recovery(CDR)circuit functions:First to recover the clock signal(CR)from the received data stream(input signal).Use the CR to perform
41、timing and amplitude-level decisions on the incoming signal.Regenerate the data stream(DR),with timing and amplitude characteristics,synchronized with the recovered clock(CR)or regenerated system clock.,Phase-Locked Loop(PLL)necessary for clock recovery:Fully integrated and does not require an exter
42、nal reference clock.Ensure alignment of the clock with the middle of a data word.Monitors the CR and provides a Loss-of-Lock(LOL)alarm when the PLL loses lock.for Optimized bit error rate(BER)adjust clock phase relative to the data signal.,Jitter specifications the real challenge for integrated CDRs
43、:Jitter specifications are recommended by the ITU/Bellcore e.g.The OC-48,2.488 Gb/s specs transmitter jitter-generation of 0.01 UIRMS(4 psRMS)and receiver jitter tolerance of 0.15 UIPk-Pk(60 psPk-Pk).One bit Unit-Interval(UI)=1/2.488Gb/s=400 ps.“Eye diagrams best illustrate the signal quality of a s
44、erial data stream this can be done directly(Measurements)or referenced to an eye mask“(Mask Test).,2023/8/21,V1.0 Confidential,70,光通信测量-CSA7000B-Clock Recovery,CSA7404B Built-in CR for optical and electrical serial data streams from 1.5 Mb/s to 2.5 Gb/sIntegrated CR in an oscilloscopeProvides single
45、-connection convenienceCan be used internally for trigger pick-offImproves internal jitter performanceEye diagram analysis and mask test with more confidenceJitter and pattern dependencies are not hidden by triggering on the data streamCR and DR Outputs(on CSA7000s only)Max 1.25 Gb/s CR and DR on outputsRecovered Clock Out(CR)and Regenerated Data Out(DR)from specified channel,available on SMA front-panel connectors for use with other test equipment(e.g.BER analyzers),
