眼图测量

Eampl(Eye)
sigma0
Zero(Eye)
Qfactor(Eye)= Eampl(Eye)/(Sigam1+Sigam2 ) SNR（Eye)=20Log（Qfactor(Eye)) BER(Eye)=0.5erfc(Qfactor(Eye)/ 2 )
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Real Time Eye (RTE):
• Is 100-1000x faster than TEP • Provides higher measurement accuracy than TEP • Trigger jitter is completely eliminated (trigger jitter = 0 ps) • CDR jitter is completely eliminated (CDR jitter = 0 ps) • Allows edge timing (jitter) measurements to be performed during eye pattern testing • Events that occur on consecutive bits are easily detected and quantified • Advanced functionality and powerful analysis are available:
Data record divided into 1 UI
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segments equal to recovered clock period
Slice 1 Slice 2 Slice 3 Slice 4 Slice 5 Slice 6 Slice 7 Slice 8 Slice 9 Slice 10 Slice 11 Slice 12
1 UI
XAUI has a bitrate of 3.125 Gb/s. Bit period = 1 UI = 1/(3.125 Gb/s) = 320 ps.
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What is an Eye Pattern?
An eye pattern is a multivalued function displayed using persistence, showing the overlay of data signal transitions. The quality of a data signal can be determined by the dimensions of the eye.
EyeBER =
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眼图形成的传统方法
同步触发＋叠加显示 同步：硬件CDR恢复பைடு நூலகம்理想时钟
Traditional Method
触发：时钟的Fo上r E升ye 沿Pat作tern为F触orm发ati源on 触发一次，叠加一个ＵＩ。
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Window
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2nd Aquisition
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3rd Aquisition
4th Aquisition
5th Aquisition
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Eye Pattern
Traditional Method For Eye Pattern Formation
(1) Eye Pattern Unfolding (Mask Violation Locator) (2) Intersymbol Interference detection and analysis (ISI plot) (3) Bit Error Rate detection and analysis (BER map) (4) Eye patterns of targeted zoom regions (math trace as SDA input) (5) Custom PLL frequency adjustment (PLL setting tab) (6) Pre-emphasized and de-emphasized bit separation (Transition eye)
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Comparing Traditional and Real Time Eye Patterns
The RTE is superior to the TEP for a multitude of reasons
Traditional Eye Pattern (TEP):
2. The eye pattern is formed from multiple acquisitions.
3. Aligning data with respect to the trigger and combining multiple acquisitions introduces instrument trigger jitter.
Continuous Bit Eye Pattern Rendering Modern Approach to Eye Pattern Test
NRZ data record acquired
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from a single trigger
Clock recovered using
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software PLL ZERO CDR JITTER
masks can be used for compliance testing
1 Unit Interval (UI) Eye patterns generally display a time window of approximately 1.25 UI
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(与触发点无关)
1
1
示波器采集 的时间窗口
0
Step 2:
每个比特被软件
恢复的时钟分离
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1
0
0
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Step 3: 把所有比特重叠得到眼
图
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Eye Pattern Displayed
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Continuous Bit Eye Pattern Rendering
Block of continuous serial data acquired
Bits are separated using software clock recovery
Overlapped bits form the eye pattern
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2. Multiple acquisitions (multiple triggers) can be used and still no trigger jitter will be introduced because data from those acquisitions are not combined using a trigger point reference.
• Is 100-1000x slower than RTE • Provides lower measurement accuracy than RTE • Introduces trigger jitter • Introduces CDR jitter (when using CDR) • Does not allow for edge timing measurements to be performed during eye pattern testing • Events that occur on consecutive bits are not detected • Provides limited functionality
Q 因子具体是由以下公式计算得到：由眼幅度（“1”电平的平均值1减去“0”电平的平均 值0） 除以“1”信号噪声有效值（1）与“0”信号噪声有效值（ 0）之和。
Q factor =
EyeBER 是通过眼图用来评估误码率的参数。 EyeBER 是计算“1”电平概率分布与“0”电平概率分布的重叠部分所占的比例，由百分比来表示 。
眼图参数
Extinction ratio: log(power(one level)/power(zero level))
One Level
Crossing Percentage
Eye Height
Eye Amplitude
Zero Level Eye Width
Q-Factor is computed by dividing the eye amplitude by the sum of standard deviations 4 of the zero and one leveLlseCroy Company Confidential
传统的眼图生成方法 ("Triggered Eye", "Single-Bit Eye"), Circa 1962 - 2002
Trigger Point
1st
Aquisition
1
同步触发＋叠加显示 同步：硬件CDR恢复出理想时钟 触发：时钟的上升沿作为触发源
触发一次，叠加一个ＵＩ
Oscilloscope Acquisition
眼图测量
So full, So fast and So powerful !
What is a Unit Interval (UI)?
A Unit Interval (UI) is the time corresponding to the period of one bit of a data signal (also the same as the reciprocal of the bitrate)
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Traditional Eye Pattern Method
Introduces Measurement Inaccuracy By Definition
1. In the traditional eye pattern, data is aligned with respect to the trigger point.
眼图参数
One(Eye) Eampl(Eye)
Zero(Eye)
3sigam1
3sigma0
Ewdth(Eye)
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眼图参数
rise
fall
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80% 20%
Q因子和眼图误码率
Q 因子是用于测量眼图信噪比的参数。 (与 OSFTP-9 标准相一致)
眼宽 眼高 眼幅度 眼交叉比 “1”电平 “0”电平 消光比 Q-factor 平均功率
眼图参数
3sigam1 One(Eye) Ehght(Eye) Eampl(Eye)
3sigma0 Zero(Eye)
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眼图参数
sigam1
One(Eye)
4. Instrument trigger jitter results in measurement inaccuracy.
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眼图形成的现代方法
同步切割＋叠加显示 示波器首先捕获一组连续比特位的信号，然后用软 件PLL方法恢复出F时or TE钟ryaed，Pitiao最tntea后rlnMF利eothrm用odat恢ion复出的时钟和 捕获到的信号按比特位切割，切割一次，叠加一次 ，最终将捕获到的一组数据的每个比特位都叠加到 了眼图上。
Segments overlayed to form
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eye pattern
ZERO TRIGGER JITTER
1. This method is immune to trigger jitter because data is aligned with the unit interval, not the trigger.
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实时眼图生成方法（Real Time Eye） ("Continuous-Bit Eye Pattern Rendering", "Single-Shot Eye"), 2002 - Presen
Step 1: 采集到一长串 连续的数据波形
眼图参数
One(Eye) 100%
Ecross(Eye)
Zero(Eye) 0%
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眼图参数
ER(Eye)=10Log(One(Eye)/Zero(Eye)
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One(Eye) Zero(Eye)