Measuring jitter of high-speed data channels
First Claim
1. A method of measuring jitter of a signal having a repetitive signal pattern, comprising the steps of:
- a. deriving a trigger from the signal;
b. comparing the signal with a threshold at a plurality of times relative to the trigger during multiple repetitions of the signal pattern to produce measurement samples indicative of signal level relative to the threshold;
c. determining from the measurement samples the probability of signal edge states as a function of time for the multiple repetitions; and
d. determining from the probability of signal edge states an edge probability density as a function of time for the multiple repetitions.
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Abstract
A jitter measurement technique utilizing a high-bandwidth undersampling voltage measurement instrument is presented. A trigger is derived from the a signal having a repetitive signal pattern. The signal is compared with a threshold at a plurality of times relative to the trigger during multiple repetitions of the signal pattern to produce measurement samples indicative of signal level relative to the threshold. The measurement samples are used to determine the probability of signal edge states as a function of time for the multiple repetitions. The probability of signal edge states are used to determine an edge probability density as a function of time. A histogram of signal state transition times can be prepared from the edge probability density. Mean deviation of edge transitions of the signal can be estimates, and standard deviation of edge transitions of the signal can be estimated to give the root-mean-square (rms) jitter of the signal.
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Citations
20 Claims
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1. A method of measuring jitter of a signal having a repetitive signal pattern, comprising the steps of:
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a. deriving a trigger from the signal;
b. comparing the signal with a threshold at a plurality of times relative to the trigger during multiple repetitions of the signal pattern to produce measurement samples indicative of signal level relative to the threshold;
c. determining from the measurement samples the probability of signal edge states as a function of time for the multiple repetitions; and
d. determining from the probability of signal edge states an edge probability density as a function of time for the multiple repetitions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. Apparatus for measuring jitter of a signal having a repetitive signal pattern, comprising:
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a. a sample probe (740) for deriving a trigger from the signal;
b. a sampler (715) having a timing generator (745) and sample probe (735) for comparing the signal with a threshold at a plurality of times relative to the trigger during multiple repetitions of the signal pattern to produce measurement samples indicative of signal level relative to the threshold; and
c. a processor (760) for determining from the measurement samples the probability of signal edge states as a function of time for the multiple repetitions, and for determining from the probability of signal edge states an edge probability density as a function of time for the multiple repetitions.
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Specification