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1 數 (Jitter) 量 1

2 Agenda 量 來 量 量 精 度 2

3 Jitter, what is it? What is jitter? the deviation of an edge from where it should be Jitter is caused by: (among other things) Thermal noise Injected noise (EMI/RFI) Circuit instabilities Transmission Losses 3

4 理 量 參 ( 理 ) ( ) 量 量 4

5 Things you should already know: Period Jitter Cycle-to-Cycle Jitter Time Interval Error (TIE) Clock Jitter Data Jitter Clock recovery BER Three Methods of Jitter Measurement 5

6 Three Methods of Jitter Measurement 參 理 兩 量 理 量 6

7 Tj Total Jitter in a signal Estimated jitter for a large population: bits 7

8 Random Jitter (RJ) 1-sigma or RMS 7-sigma 8

9 Deterministic Jitter (DJ) Peak-to-Peak 9

10 Periodic Jitter (PJ) Peak-to-Peak 10

11 Duty Cycle Distortion (DCD) 不 降 0.0v Peak-to-Peak 11

12 Data-Dependent Jitter (DDJ or ISI) 參 數 料 率 12

13 BER Bit Error Rate Ratio of good bits to bad bits Send 1,000,000,000,000,000,000,000 bits Receive 999,999,999,999,999,999,999 bits correctly Yields a BER of 1:10-21 (1x10-21 or 1E -21 ) Requires sending as many bits as you are testing for! You must capture all bits in sequence for this test to be valid, only a BERT can do this! 13

14 Unit Interval and Bit Error Rate BER: Ratio of good bits to bad bits Generally specified at bits UI: the nominal period of one transmitted bit 14

15 度 累 率 度 數 數 例 度 度 度 1-sigma or RMS 7-sigma 15

16 Total BER pdf : Tj = Dj Rj (convolution) Pk-Pk: Tj = (N*Rj) + Dj, where N =2*Z Deterministic components Peak-to-Peak 1-sigma or RMS Random components 16

17 Statistics Theorem: Sum of Two Independent RVs(Random Variable) If two RV s are independent, the pdf of the sum is the convolution of the respective pdfs = Central Limit Theorem If N RV s are independent, the pdf of the sum is Gaussian as N infinity 17

18 Histograms vs. Eye Diagrams How open is the eye, anyway? ( depends how long you watch) Eye Opening=? 18

19 Eye Opening vs. Bit Error Rate Probability Density Function (pdf) Cumulative Distribution Function (cdf) Eye Open for BER 1:

20 BER Estimation using Eye Diagram Statistics 20

21 Bath Tub Curve Start with TIE PLL TIE Perform FFT Determine frequency and pattern rate Sum pattern related bins Sum unrelated periodic bins Measure RMS of remaining bins Estimate BER 21

22 TDSJIT3 Factory Correlation 4 BERT Correlation 0 A tool is useless if it doesn t agree with accepted standards 0 TDSJIT3 correlates to a BER Tester within 2% to 3% Results for PRBS-7 Data Pattern Raw Noise (10ps rms) Sinusoidal (100KHz) Sinusoidal (50MHz) JIT3 BERT Diff JIT3 BERT Diff JIT3 BERT Diff JIT3 BERT Diff Freq G G G G G G G G 0.0 PRBS-7 BER eye open eye open eye open eye open (127 bits) 1.00E E E E E E E RJ 3.34ps Noise/Com 22db 7.79ps Noise/Com 12db 5.93ps Noise/Com 17db 5.78ps Noise/Com 17db DJ 24.34ps Sine 27.88ps Sine 56.78ps Sine 53.86ps Sine PJ 5.23ps Freq 100K 3.96ps Freq 100K 37.90ps Freq 100K 33.31ps Freq 50M DCD 4.60ps Mag 1mv 6.10ps Mag 1mv 4.08ps Mag 150mv 4.63ps Mag 150mv DDJ 14.52ps 17.82ps 14.80ps 15.92ps difference in %UI exterpolated 22

23 領 量 路 料 來 度 量 串 料 來 23

24 來 不連 串 24

25 量 利 量 量 25

26 來 量 易 易 量 不 易 料 力 26

27 量 來 量 更 易 量 不 料 量 不 力 27

28 不 來 量 易 量 精 料 料 易 力 28

29 量 數 量 8 累 29

30 量 參數 30

31 量 數 量 累 量 參 不 P1 P2 Period = X1-T,X2-X1,X3-X2,,Xn-Xn-1 T X X X X X X X X T X X X X X X X X 31

32 量 參數 列 例 量 參數 類 參數 量 參數 32

33 量 參數 列 量 參數 料 料 類 參數 量 參數 33

34 量 參數 量 參數 列 數 參數 34

35 錄 來 錄 度 35

36 量 累 量 數 不 量 狀 36

37 量 量 量數 量 37

38 量 量 量數 量 38

39 率 易 率 39

40 累 數 率 累 數 易 40

41 量 精 度 量 精 度 量 度 量 度 度 精 度 41

42 精 度 量 參數 量 量 度 不 量 參 不 度 度 精 度 量 42

43 精 度 4 例 率 精 度 量 精 度 精 度 略不 精 度 來 43

44 44 TDSJIT3 Software Overview

45 TDSJIT3 User Interface Measurement Selection Clock Data Clk-Data General Users can select measurements from any source Channel, Math, Ref User can select the same measurement on multiple channels: Period(Ch1), Period(Ch2), Period(Ch3), Period(Math1) 45

46 TDSJIT3 Configuration Configuration Meas Params Source Autoset Gate/Qualify Ref Levels Population Limit Users configure each Source and Measurement independently Each source has its own settings Each measurement has its own settings 46

47 TDSJIT3 Autosetting Vertical Autoset Intended to maximize vertical dynamic range Each source can be set independently Horizontal Autoset Adjusts horizontal settings to ensure reliable results based on signal risetime Vert and Horiz Autoset are really fine tuning controls, I normally recommend customers set scope manually for best results 47

48 TDSJIT3 Gates and Qualifiers Gate Measurements are made only inside gated region Gate by Cursor Gate by Zoom Limits single shot population hence Rj/Dj capability Qualify Measurements are made only when Qualify input has transitions and state meets criteria 48

49 TDSJIT3 Reference Levels Sets thresholds for making measurements Each source has its own settings for rising and falling edges Autoset-Setup allows changing levels by percentage (e.g., 10-90%) Autoset All Active is a quick way to go and ensures good results 99% of the time Hysteresis is an important setting, especially in noisy environments 49

50 TDSJIT3 Population Limit Sets population limit for making measurements Measurement stops when limit reached In Run mode (continuous), acquisitions stop when population limit reach A handy and customer desired feature 50

51 TDSJIT3 Summaries Shows a summary of measurements, their configurations and reference levels Handy place to review how the software is configured 51

52 TDSJIT3 Results Views Results are displayed differently in TDSJIT3 Results are shown in different views: All Statistics Min/Max Mean/StdDev TIE Rj/Dj BER 52

53 TDSJIT3 All Statistics Each measurement is selected independently only results for one measurement are shown All statistics are shown for the selected measurement The first column is the last acquisition The second column is the accumulation of all acquisitions Clear erases all data Max +/- show the largest pos/neg change on a cycle to cycle basis for every measurement type! 53

54 TDSJIT3 TIE: Rj/Dj - BER Displays results for Rj/Dj Rj/Dj results are only available for TIE and PLL TIE measurements Rj/Dj is a two step process: make the TIE measurement; then calculate Rj/Dj Rj/Dj requires a repeating pattern, such that 100 repeats are captured in a single acquisition You must know and enter the pattern length Rj is RMS, Dj is Pk-Pk, Tj is Pk-Pk 54

55 TDSJIT3 Plot Creation Users can create up to 4 plot windows Windows can be dragged to second monitor Once created, plot and scope views are manipulated using inwindow controls or Select View pop-up Plots no longer use Ref memories 55

56 TDSJIT3 Plot Window Controls Plot windows controls Update On/Off Position Top/Bottom Select View Zoom or Cursor Mode 56

57 TDSJIT3 Data Logging Logging comes in three flavors Statistics Logging a history of each measurement result and statistics Measurement Logging a snapshot of the current measurements plus the full data array that was used Worst Waveform Logging a snapshot of the waveform that contained the worst measurement logging measurements can take huge amounts of disk space be careful what you ask for 57

58 58 Demo TDSJIT3 Software