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DSO80204B Jitter Measurement

Question asked by igouzouasis on Apr 17, 2013
Latest reply on Apr 18, 2013 by algoss

I have a DSO80204B 40Gsa/s Infiniium and want to measure jitter of an oscillator. The scope has no jitter-specific measurement functions, so thought to try an histogram. Consider attached image. I placed a 52MHz wave uniformly above and below zero (removed dc offset) and used high memory depth. Jitter looks random with a gaussian like shape. I have two things to ask.

1) It's commonly said that rms jitter is the standard deviation of the histogram. However, if I'm not mistaken, RMS Jitter is the rms deviation from the ideal transition, meaning having zero mean. Histogram's mean is not zero (see attached) and also by definition, standard deviation is computed from the squares of the *difference* of each point from the mean (Xi-mean)^2. In other words, it should be that rms jitter is the standard deviation when the mean is zero, and consequently stdev of the histogram is *not* the rms jitter. Am I loosing something?

2) The histogram measurement is subjected to the scope's trigger jitter, meaning the ability of the scope to be triggered and acquire data point very quickly. To what extent the trigger jitter affects the measurement-what are the limits? Am I assured that a 200fs measurement is accurate?