On 03/14/2012 11:22 AM, Attila Kinali wrote:
Hi,
I'm currently writing a short article on crystal oscillators and am
looking for plots of "typical" phase noise and ADEV of an OCXO.
But unfortunately, i couldnt find any, so far. Only discrete numbers
from the data sheets, or phase noise plots only from scientific papers.
Does anyone have something like this at hand?
I know I should add one to the Wikipedia Allan Deviation article. Let me
know if there is anything other which is missing in that article so I
can add to it.
What you should have is essentially a bath-tub curve with a 1/tau slope
for the white phase modulation (WPM) noise, a roughly 1/sqrt(tau) slope
from the flicker phase modulation (FPM) or white frequency modulation
(WFM) and then a flat part due to the flicker frequency modulation
(FFM). See the table in [1].
At higher tau the systematic effect of frequency drift comes in, and if
included into the Allan Deviation it rises with tau [2]. As a systematic
effect, it should not really be included into the ADEV plot, but you
usually see it in practical measurements.
[1] http://en.wikipedia.org/wiki/Allan_variance#Power-law_noise
[2] http://en.wikipedia.org/wiki/Allan_variance#Linear_response
The existence of WFM and FFM noises is due to the Leeson model.
Cheers,
Magnus
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