Method for performing joint jitter and amplitude noise analysis on a real time oscilloscope

Patent metadata

Field	Value
Publication number	US-9294237-B2
Application number	US-201414552265-A
Country	US
Kind code	B2
Filing date	Nov 24, 2014
Priority date	Jul 30, 2014
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

A method for determining jitter and noise of an input signal. The method includes acquiring one or more uncorrelated waveform records by an acquisition unit of a test and measurement instrument, determining a correlated waveform from the acquired waveform(s), dividing the correlated waveform into unit intervals, dividing an uncorrelated waveform into unit intervals, measuring a timing displacement (t 1 ) between the correlated waveform and the uncorrelated waveform for each unit interval to form an apparent-jitter array ([t 1 ]), measuring a voltage displacement (V 1 ) between the correlated waveform and the uncorrelated waveform for reach unit interval to form an apparent-noise array ([V 1 ]), calculating a horizontal shift (t s ) between the correlated waveform and the uncorrelated waveform for each unit interval to form a compensated edge time array ([t s ]), and calculating a vertical shift (V s ) between the correlated waveform and the uncorrelated waveform for each unit interval to form a compensated amplitude voltage array ([V s ]).

First claim

What is claimed is:

1. A method for determining jitter and noise of an input signal, comprising:
acquiring at least one uncorrelated waveform record by an acquisition unit of the test and measurement instrument;
determining a correlated waveform based on the at least one uncorrelated waveform;
dividing the correlated waveform into unit intervals;
dividing the at least one uncorrelated waveform into unit intervals;
measuring a timing displacement (t 1 ) between the correlated waveform and the uncorrelated waveform for each unit interval to form an apparent-jitter array ([t 1 ]);
measuring a voltage displacement (V 1 ) between the correlated waveform and the uncorrelated waveform for each unit interval to form an apparent-noise array ([V 1 ]);
calculating a horizontal shift (t s ) between the correlated waveform and the uncorrelated waveform for each unit interval to form a compensated edge time array ([t s ]); and
calculating a vertical shift (V s ) between the correlated waveform and the uncorrelated waveform for each unit interval to form a compensated amplitude voltage array ([V s ]),
wherein the horizontal shift and the vertical shift are calculated for each unit interval using the following equations:
t s =( V 1 +SR V *t 1 )/(SR V −SR H ), and

V s =V 1 +SR H *t s ,

wherein SR V represents a slew rate of the uncorrelated waveform on a vertical portion of the uncorrelated waveform and SR H represents the slew rate of the uncorrelated waveform on a horizontal position of the uncorrelated waveform.

2. The method of claim 1 , wherein the horizontal shift is calculated for each transition bit unit interval and set to 0 for each non-transition bit unit interval.

3. The method of claim 1 , wherein the horizontal shift is calculated for each transition bit unit interval using the equation for t s and the horizontal shift is calculated for each non-transition bit unit interval using nearby preceding and subsequent unit interval horizontal shifts by interpolation.

4. The method of claim 1 , further comprising filtering, using a low-pass filter, the timing displacement and the voltage displacement prior to calculating the horizontal shift and the vertical shift.

5. The method of claim 1 , wherein the equation for t s is calculated a plurality of times, using a plurality of slew rates, and the method further includes selecting one of the plurality of calculated t s values for each unit interval based on a resultant jitter estimate.

6. The method of claim 1 , further comprising generating a two-dimensional probability density function of uncorrelated noise using the apparent-jitter array, the apparent noise array, the compensated edge time array, and the compensated amplitude voltage array.

7. The method of claim 6 , further comprising generating a bit error rate diagram based on the generated two-dimensional probability density function.

8. The method of claim 1 , further comprising generating a bit error rate diagram based on the apparent-jitter array, the apparent-noise array, the compensated edge time array, and the compensated amplitude voltage array.

9. The method of claim 1 , wherein the test and measurement instrument is a real-time oscilloscope.

10. A test and measurement instrument, comprising
acquisition means configured to receive at least one uncorrelated waveform record; and
processing means for:
determining a correlated waveform based on the at least one uncorrelated waveform;
dividing the correlated waveform into unit intervals;
dividing the uncorrelated waveform into unit intervals;
measuring a timing displacement (t 1 ) between the correlated waveform and the uncorrelated waveform for each unit interval to form an apparent-jitter array ([t 1 ]);
measuring a voltage displacement (V 1 ) between the correlated waveform and the uncorrelated waveform for each unit interval to form an apparent-noise array ([V 1 ]);
calculating a horizontal shift (t s ) between the correlated waveform and the uncorrelated waveform for each unit interval to form a compensated edge time array ([t s ]); and
calculating a vertical shift (V s ) between the correlated waveform and the uncorrelated waveform for each unit interval to form a compensated amplitude voltage array ([V s ]),
wherein the horizontal shift and the vertical shift are calculated for each unit interval using the following equations:
t s =( V 1 +SR V *t 1 )/(SR V −SR H ), and

V s =V 1 +SR H *t s ,

wherein SR V represents a slew rate of the uncorrelated waveform on a vertical portion of the uncorrelated waveform and SR H represents the slew rate of the uncorrelated waveform on a horizontal position of the uncorrelated waveform.

11. The method of claim 10 , wherein the processing means is further configured to generate a two-dimensional probability density function of uncorrelated noise using the apparent-jitter array, the apparent noise array, the compensated edge time array, and the compensated amplitude voltage array.

12. The method of claim 11 , wherein the processing means is further configured to generate a bit error rate diagram based on the generated two-dimensional probability density function.

13. The method of claim 10 , wherein the processing means is configured to generate a bit error rate diagram based on the apparent-jitter array, the apparent-noise array, the compensated edge time array, and the compensated amplitude voltage array.

Assignees

• Tektronix Inc

Inventors

• Guenther Mark L
• Tan Kan

Classifications

• H04L1/205 Primary

  jitter monitoring · CPC title

• G01R31/31709

  Jitter measurements; Jitter generators (measuring jitter, noise figure or signal-to-noise ratio per se G01R29/26; analysis of tester signals G01R31/31901) · CPC title

• G01R31/31711

  Evaluation methods, e.g. shmoo plots · CPC title

• G01R13/0272

  for sampling · CPC title

• G01R29/26

  Measuring noise figure; Measuring signal-to-noise ratio · CPC title