Teledyne LeCroy Jitter Basics Lab Using Jitter Sim page | 1 of 13

Jitter Basics Lab Using SDAIII & Jitter Sim TUTORIAL August 1, 2012

Summary

JitterSim is a math function,

enabled by the Serial Data

Analysis option, which allows

various aspects of jitter to be

simulated either singly or in

groups. It is ideal for

experimenting with how

various jitter components are

manifested in the jitter

measurement displays

available in SDAIII.

Powerful SDAIII Serial Data Analysis

Unleash the power of serial data analysis to understand and characterize

your design, prove compliance, and determine why a device or host fails

compliance. The SDAIII analysis package is the only solution that fully

integrates jitter measurements into the oscilloscope software leading to

greater confidence in jitter measurements.

Key Features

Integrated jitter and timing analysis for clock and data signals

Many plot types for jitter and eye diagram analysis including: Eye

Diagram, IsoBER, DDj Plot, Digital Pattern, DDj Histogram, Jitter

Track, PLL Track, Jitter Spectrum (with peak annotation),

Spectrum Threshold, Pj Inverse FFT, Jitter Histogram, CDF,

Bathtub, and NQ-Scale

IsoBER displays the lines of constant Bit Error Ratio

Configurable software PLL uses up to two poles for non-standard

clock requirements

Three jitter breakdown methods (Spectral Rj Direct, Spectral Rj+Dj

CDF Fit and NQ-Scale) indicate pathological jitter measurement

conditions

Teledyne LeCroy’s quick view displays the eye diagram, TIE track,

bathtub curve, jitter histogram, NQ-scale, and jitter spectrum all on

the screen at the same time

Eye diagram display and jitter measurements/analysis on up to

four lanes of serial data

Complete Data Dependent Jitter (DDj) decomposition with

histograms, plots, and InterSymbol Interference (ISI) parameters

and plots

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Complete Random Jitter (Rj) + Bounded Uncorrelated Jitter (BUj) views include Histogram, Spectrum and

Track

Complete Period Jitter (Pj) analysis with a time domain view of Pj (Pj Inverse FFT)

A new Vertical Noise and Crosstalk package that determines total noise due to interference caused by

crosstalk, and decomposes it into random and deterministic noise

The LaneScape Comparison mode and Reference Lane for aggressor on/off and other multi-scenario

comparisons

The ability to determine what the signal will look like where you cannot place the probe, while also de-

embedding or emulating up to 6 circuit elements

Equipment Required

Teledyne LeCroy WavePro/SDA/DDA 7 Zi/Zi-A, WaveMaster/SDA/DDA 8 Zi/Zi-A, LabMaster 9 Zi-A and 10 Zi

series oscilloscopes with the SDAIII Serial Data Analysis option enabled. Screen images in this tutorial were

taken from a WaveMaster 820Zi-A

Tutorial

1. Recall the default setup on the scope (File>Recall Setup>Recall Default).

2. Turn off channels 1 and 2 using the front panel 1 and 2 buttons in the vertical control group or by

accessing the C1 and C2 dialog boxes via the vertical pull down.

3. Using the Timebase Horizontal setup (Timebase > Horizontal Setup, set the WM8Zi for operation with a

sampling rate of 40 GS/s and 800kS acquisition memory (2 s Time/division).

4. Setup Math trace F1 to use the Jitter Sim function (Math> Math Setup>F1>Source C2>Operator Jitter

Sim). Turn the F1 trace on.

5. Using the Sim Signal right hand tab of the F1 dialog box setup Sim Signal to use a frequency of 2.48

GHz, a risetime of 200 ps, and NRZ data type. The screen should appear similar to Figure 1.

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Figure 1: The JitterSim setup

6. Open the SDAIII setup dialog and display (Analysis pull down > Serial Data).

7. On the Serial Data Analysis III dialog box press the Quick View button. A pop up will appear as shown in

Figure 2.

Figure 2: The Quick View Input selection pop up box

8. In the QuickView pop press the “1 Input’ button and select F1 as the data source. Press OK.

9. The oscilloscope will bring up the Quick View display consisting of the Eye diagram, PLL Track, Jitter

Spectrum, Bathtub curve, RjBUj histogram, Q scale, and RjBUj Track. This is shown in Figure 3.

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Figure 3: The SDAII Quick View Display setup

10. JitterSim allows the users to independently simulate various aspects of jitter. This includes jitter

associated with vertical noise, random horizontal jitter, sinusoidal periodic jitter, duty cycle distortion

(DCD), and Inter-Symbol Interference (ISI). Our initial measurements are made with the default jitter

separation model, Spectral Rj+Dj CDF Fit.

Record the values of the parameters Tj, Rj, and Dj from the scope display

_Tj ________________ Rj _________________ Dj ________________

11. As a first step let’s see what happens if we increase the vertical (Rn) noise on the Vertical tab in Jitter

Sim. Open the F1 dialog box (Math > Math Setup > F1 tab > Vertical right hand tab. Change the

Gaussian vertical noise level to 5 mV and record Tj, Rj, and Dj:

_Tj ________________ Rj _________________ Dj ________________

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Describe what happened to the Normalized Q-Scale, Bathtub Curve, Eye Diagram, RjBUj track, and

histograms

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Figure 4: Effect of Increasing Vertical Noise

12. You know that vertical noise maps into horizontal jitter proportional to the risetime of the data. Increase

the Risetime setting on the Sim Signal tab to 400 ps (F1 > Sim Signal right hand tab).

13. Record Tj, Rj, and Dj

_Tj ________________ Rj _________________ Dj ________________

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14. Describe what happened to the Normalized Q-Scale, Bathtub Curve, Eye Diagram, RjBUj track, and

histograms

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Figure 5: Increased vertical noise along with increased risetime

15. Restore both the Gaussian vertical noise level to 1 mV and risetime to 200 ps.

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16. Let’s add periodic jitter. Go to the Jitter right hand tab of the F1 dialog box and set the Jitter Freq setting

on the first line of the sinusoidal jitter field to 1 MHz with a Peak to Peak level of 5 ps. Record Tj, Rj, and

Dj here and on the following page.

_Tj ________________ Rj _________________ Dj ________________

Describe what happened to the Normalized Q-Scale, Bathtub Curve, Eye Diagram, RjBUj track, and

histograms

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Figure 6: The effect of adding periodic jitter

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17. Repeat this test for Peak to Peak levels of 10 ps and 20 ps.

5 ps _Tj ________________ Rj _________________ Dj ________________

10 ps _Tj ________________ Rj _________________ Dj ________________

20 ps _Tj ________________ Rj _________________ Dj ________________

18. Save and compare the Bathtub curves for each level of sinusoidal periodic jitter into memories M1-M3.

File > Save Waveform> Save To Memory> Source> Category>SDA> Source Bathtub> Destination > M1

(then M2 and M3)>

What effect does increasing Deterministic (periodic) jitter have on the bathtub curve

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Figure 7: The saved Bathtub curve for 5 ps (M1), 10 ps (M2), and 20 ps (M3) periodic jitter amplitudes

19. Turn off the memory traces. Restore the QuickView Display (Analysis > Serial Data >QuickView

 

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20. Touch or click the RjBUj Spect trace annotation box. Use the Zoom of RjBUj Spect right hand tab to

setup the zoom on the RjBUj Spectrum to show the periodic jitter component at 1 MHz as shown in

Figure 8. Turn on Show Peaks in the Jitter Spectrum tight hand tab.

Figure 8: The periodic component shown on the RjBUj spectrum display

21. Restore the Peak to Peak level of the sinusoidal component in JitterSim to 0 ps

22. We will now see the effect of Duty Cycle Distortion (DCD) on jitter levels.

Set the DCD under the Vertical tab to 40 ps. Record Tj, Rj, and Dj

_Tj ____________ Rj _________________ Dj ________________ DCD ______________

Describe what happened to the Normalized Q-Scale, Bathtub Curve, Eye Diagram, RjBUj track, and

histograms

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23. Restore the DCD to 0 ps.

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Figure 9: Investigating the effects of DCD

24. We will now see the effect of Intersymbol Interference (ISI) on jitter levels. We will use a low pass filter to

create ISI. On the Sim Signal tab set the Cutoff Frequency to 1.8 GHz and Order to 3. Check the box

labeled BWL (Band width limit ) On.

Record Tj, Rj, and Dj

_Tj ________________ Rj _________________ Dj ________________ ISI_________________

Describe what happened to the Normalized Q-Scale, Bathtub Curve, Eye Diagram, RjBUj track, and histograms

_________________________________________________________________________________________

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Figure 10: How ISI affects jitter levels

25. Open the Math trace F1 dialog box. Set the jitter simulation parameters as follows:

F1 Tab Function Values

Jitter Sinusoidal Jitter Jitter frequency 1 MHz, Pk-Pk 5 ps

Vertical Rn (Gaussian) 5 mV

Sim Signal Riwetime 200 ps

BWL On

CutOff 1.8 GHz

Order 2

Vertical DCD 40 ps

26. Record Tj, Rj, and Dj

_Tj ________________ Rj _________________ Dj ________________

The display should appear similar to Figure 11.

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Figure 11: The Spectral Rj+Dj CDF Fit measurement

27. Open the SDA dialog box (Analysis>Serial Data). Click on the Jitter tab. Change the Dual-Dirac Model

from Spectral Rj+Dj CDF Fit to NQ-Scale. The display should be similar to Figure 12.

28. Record Tj, Rj, and Dj

_Tj ________________ Rj _________________ Dj ________________

Figure 12: The NQ-Scale measurement

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29. Change the Dual-Dirac Model from NQ-Scale to Spectral Rj Direct. The display should be similar to

Figure 13.

30. Record Tj, Rj, and Dj

_Tj ________________ Rj _________________ Dj ________________

Figure 11: Spectral Rj Direct model

Note that the jitter measurements using the three models are similar, but they can be quite different depending on

the type of jitter present. For example, when there is crosstalk, the two Spectral methods will report high values

of Rj due to the rise in the noise floor of the jitter spectrum. Variations of this magnitude among the model

responses, in the absence of crosstalk, can be expected and are explained in the Teledyne LeCroy White Paper:

“Understanding SDAlIl Jitter Calculation Methods”

This completes the tutorial.