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Measurements >> Phase Noise and Jitter Measurements >> deducing phase noise of XTAL oscillators
https://designers-guide.org/forum/YaBB.pl?num=1177068420

Message started by vivkr on Apr 20^th, 2007, 4:26am

Title: deducing phase noise of XTAL oscillators
Post by vivkr on Apr 20^th, 2007, 4:26am

Hi,

I am trying to choose a low-jitter XTAL oscillator for my ADC measurement. However, the
problem is that XTAL vendors ask for specs such as RMS jitter for an observation interval
of 1 sec, whereas my measurement span is more like 10 ms.

I assume that the variance (RMS jitter)^2 = 2*D*T (where D is some const., T the observation interval), and that
the noise of a high purity XTAL is a random walk.

Example: if the XTAL has a measured RMS jitter of say 1 ps in T = 1s, then over T=10ms, I can expect 100 fs RMS jitter,
or less, since the profile of phase noise goes up faster than 1/f^2 in reality.

Is my understanding correct? Can I use these criteria to compute the phase noise and RMS jitter specs for a XTAL osc,
and give these to the vendor. In this case, I asked Wenzel because they are known to make really good oscillators.

Thanks
Vivek