Measuring components of jitter

• US 20060251200A1
• Filed: 02/24/2006
• Published: 11/09/2006
• Est. Priority Date: 02/25/2005
• Status: Active Grant

• Current Assignee: Teledyne LeCroy, Inc. (Teledyne Technologies Incorporated)
• Original Assignee: Lecroy Corporation (Teledyne Technologies Incorporated)
• Inventors: Miller, Martin Thomas
• Granted Patent: US 7,516,030 B2
• Time in Patent Office: Days
• US Class Current: 375/371
• CPC Class Codes: G01R 29/26 Measuring noise figure; Measuring signal-to-noise ratio
• CPC Class Codes: G01R 31/31709 Jitter measurements; Jitter generators measuring jitter, noise figure or signal-to-noise ratio per se G01R29/26; analysis of tester signals G01R31/31901
• CPC Class Codes: H04L 1/205 jitter monitoring

Abstract

Apparatus and associated systems, methods and computer program products relate to isolating horizontal jitter component(s) from vertical jitter component(s). In preferred embodiments, at least one horizontal component of jitter is distinguished from at least one component of vertical jitter by fitting a curve to a digitally acquired waveform, determining the curve slope and statistical variance about the fitted curve over at least one time period, identifying a functional relationship between the variance and slope, and determining therefrom at least one horizontal component of jitter and at least one vertical component of jitter. Random and deterministic jitter components may be aggregated, in certain embodiments, so as to identify a vertical jitter component that reflects both deterministic and random jitter. In preferred implementations, the isolated vertical jitter component is subtracted from a total jitter measurement so as to better approximate actual signal jitter.

Claims

1. A digital oscilloscope comprising:

a channel to receive a signal having a repeating pattern that includes a sequence of transitions, said signal having jitter;

an acquisition module to acquire a plurality of digital samples of the signal over a plurality of occurrences of said repeating pattern;

a processor;

a first plurality of memory locations to store the acquired samples; and

a second plurality of memory locations coupled to the processor to store executable instructions that, when executed by the processor, cause operations to be performed on the digital samples stored in the first plurality of memory locations to resolve the jitter into a plurality of components, said operations comprising;

i) determining at least one horizontal component of said jitter; and

ii) determining at least one vertical component of said jitter, said vertical component being distinct from said horizontal component.

2. The apparatus of claim 1, said operations further comprising determining a total signal jitter.

3. The apparatus of claim 2, wherein the total signal jitter consists essentially of a horizontal component and a vertical component.

4. The apparatus of claim 1, wherein said operations further comprise identifying a single vertical component of said jitter.

5. The apparatus of claim 1, wherein said signal is periodic.

6. The apparatus of claim 1, wherein said operations further comprise identifying an amount of intrinsic jitter added by the channel.

7. The apparatus of claim 6, wherein said operations further comprise determining a signal jitter by quadrature subtraction of the intrinsic jitter from a measured total jitter.

8. The apparatus of claim 7, wherein the signal jitter corresponds substantially to horizontal jitter and the intrinsic jitter corresponds substantially to vertical jitter.

9. The apparatus of claim 8, wherein the intrinsic jitter comprises thermal noise.

10. The apparatus of claim 1, wherein said operations further comprise generating an eye diagram from the sampled patterns.

11. The apparatus of claim 1, wherein said operations further comprise generating a probability distribution function upon processing the processing the digital samples.

12. The apparatus of claim 1, wherein said operations further comprise fitting a curve to the acquired samples.

13. The apparatus of claim 12, wherein said operations further comprise determining a slope of the fitted curve.

14. The apparatus of claim 12, wherein said operations further comprise determining a variance of a residual of the fitted curve.

15. The apparatus of claim 12, wherein said operations further comprise identifying a plurality of periods in the repeating pattern and associating the acquired samples with a phase in one of the identified periods.

16. The apparatus of claim 12, wherein said operations further comprise interleaving the associated samples with each of the identified periods.

17. The apparatus of claim 15, further comprising a trigger module to receive a synchronization signal generated synchronously with the signal received in the channel, said trigger module providing timing information to identify the plurality of periods.

18. The apparatus of claim 1, wherein the signal received in the channel comprises a data signal.

19. The apparatus of claim 1, wherein the signal received in the channel comprises a clock signal.

20. The apparatus of claim 1, further comprising a display device for displaying a representation of the determined at least one horizontal component of said jitter and the isolated at least one vertical component of said jitter.

21. A method of measuring jitter with an oscilloscope, the method comprising:

receiving on a channel of a digital oscilloscope a signal having a repeating pattern that includes a sequence of transitions, said signal having jitter;

acquiring a plurality of digital samples of the signal over a plurality of occurrences of said repeating pattern; and

processing the digital samples to resolve the jitter into a plurality of components, said processing comprising;

i) determining at least one horizontal component of said jitter; and

ii) isolating at least one vertical component of said jitter from said horizontal component.

22. The method of claim 21, further comprising determining a total signal jitter.

23. The method of claim 22, further comprising identifying an amount of intrinsic jitter added by the channel.

24. The method of claim 23, further comprising determining a signal jitter by quadrature subtraction of the intrinsic jitter from a measured total jitter.

25. The method of claim 21, further comprising fitting a curve to the acquired samples.

26. The method of claim 25, further comprising determining a slope of the fitted curve.

27. The method of claim 25, further comprising determining a variance of a residual of the fitted curve.

28. The method of claim 21, further comprising generating an eye diagram from the sampled patterns.

29. The method of claim 21, further comprising generating a probability distribution function upon processing the digital samples.

30. The method of claim 21, further comprising generating a bathtub curve from the sampled patterns.

31. The method of claim 21, further comprising determining a deterministic jitter.

32. The method of claim 31, wherein the determined deterministic jitter is associated with the jitter on the received signal.

33. The apparatus of claim 21, wherein said operations further comprise determining a random jitter.

34. The method of claim 33, wherein the determined random jitter is associated with the jitter on the received signal.

35. The method of claim 21, wherein said processing further comprises determining at least one component of the horizontal component that comprises horizontal jitter introduced by the digital oscilloscope.

36. The method of claim 21, wherein said processing further comprises determining at least one component of the vertical component that comprises vertical jitter present in the received periodic signal.

37. The method of claim 21, further comprising identifying a bit error rate specification and determining the variance associated with the specified bit error rate.

38. The method of claim 21, further comprising acquiring the waveform using coherent interleaved sampling.

39. The method of claim 21, further comprising triggering the samples based on a clock signal synchronized to the received waveform.

40. The method of claim 21, further comprising post-processing the received waveform to identify periods.

41. The method of claim 28, wherein generating the eye diagram comprises synchronizing and overlaying the periods.

42. The method of claim 21, wherein the processing is performed without receiving information extrinsic to the received signal itself about the frequency of the received signal.

43. The method of claim 21, wherein the processing is performed without receiving information extrinsic to the received signal itself about the pattern of the received signal.

44. The method of claim 21, wherein the processing is performed without receiving information extrinsic to the received signal itself about the coding of the received signal.

45. The method of claim 21, wherein the processing is performed without receiving information extrinsic to the received signal itself about the encryption of the received signal.