Transport delay and jitter measurements
First Claim
1. A method of measurements comprising the steps of:
- acquiring waveforms at two test points of a system under test;
running constant clock recovery on both waveforms to obtain respective offset values;
computing a time offset between the respective offset values;
filtering jitter from the two test points;
computing a mean-removed cross-correlation coefficient between the filtered jitter from the two test points; and
computing a transport delay by summing the time offset and mean-removed cross-correlation coefficient.
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Abstract
A method of measuring transport delay and jitter with a realtime oscilloscope using cross-correlation acquires waveforms from two test points in a system under test. Clock recovery is run on both waveforms to obtain respective rates and offsets. A time offset between the two waveforms is computed. The jitter from the two test points is filtered and a mean-removed cross-correlation coefficient is computed from the filtered jitters. A fractional delay is computed using interpolation based on LMS error, and the respective computational components are summed to compute a transport delay between the two test points. The transport delay may be used to adjust clock edges from one waveform for comparison with data transition edges of the other waveform to measure jitter.
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Citations
5 Claims
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1. A method of measurements comprising the steps of:
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acquiring waveforms at two test points of a system under test; running constant clock recovery on both waveforms to obtain respective offset values; computing a time offset between the respective offset values; filtering jitter from the two test points; computing a mean-removed cross-correlation coefficient between the filtered jitter from the two test points; and computing a transport delay by summing the time offset and mean-removed cross-correlation coefficient. - View Dependent Claims (2, 3, 4, 5)
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Specification