[time-nuts] Noise types and Allan Deviation

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Jan 14 21:49:03 UTC 2009


Tom Van Baak wrote:
> A number of you have asked about Allan deviation recently so
> I thought I'd share this handy one-page chart that shows both
> ADEV and MDEV for the following noise types:
>
> - white phase
> - flicker phase
> - white frequency
> - flicker frequency
> - random walk frequency
>
> http://www.leapsecond.com/notes/Exploring_Allan_Deviation.pdf
>
> It's in high resolution PDF format so if it looks blurry on your
> screen either zoom by 2x or just print it on a laser printer.
>
> /tvb
>
>
>
>   
Tom

A table indicating the dependence of the ADEV of these phase noise types
on the measurement system bandwidth would also be helpful.

There seems to be some general confusion about this.
In general, the measured ADEV, MDEV, etc., depends both on the phase
noise characteristics of the 2 oscillators being compared and on the
measurement system characteristics.

Thus without correction for the effect of the measurement system noise
bandwidth, 2 different measurement systems measuring the same oscillator
pair will produce different results even though both measurement systems
are working correctly.

Bruce




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