Continuous Bit Eye Pattern Rendering Modern Approach to Eye Pattern Test
NRZ data record acquired
1
from a single trigger
Clock recovered using
2
software PLL ZERO CDR JITTER
Block of continuous serial data acquired
Bits are separated using software clock recovery
Overlapped bits form the eye pattern
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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):
Window
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0
1
0
1
1
2nd Aquisition
1
0Leabharlann 1011
0
3rd Aquisition
4th Aquisition
5th Aquisition
13
1
0
0
1
0
0
0
1
0
0
0
0
0
1
1
1
0
1
1
0
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Eye Pattern
Traditional Method For Eye Pattern Formation
(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
1
1
0
0
1
1
0
1
1
Step 3: 把所有比特重叠得到眼
图
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0
Eye Pattern Displayed
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Continuous Bit Eye Pattern Rendering
• 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
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)
(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)
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恢复出理想时钟
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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Segments overlayed to form
4
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
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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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.
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。
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)
Data record divided into 1 UI
3
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
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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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.