[time-nuts] Close-in phase noise measurements

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Mar 31 00:54:44 EDT 2008


Richard (Rick) Karlquist wrote:
> The relationship between phase noise and Allan variance is
> a complex one and was described in papers at FCS in 1976
> and 1978 by my previous manager Mike Fischer (then of HP).
> I think these papers come closest to answering your question.
>
> Rick Karlquist
>
>   
Essentially the mapping from phase noise to Allan variance isnt 1 to 1.

AVAR formula

Whilst it is possible to calculate the Allan variance from the phase 
noise spectrum using the above formula or a variant thereof,
the reverse isnt an unambiguous process as it is possible for different 
phase noise spectra to have the same Allan variance.
In practice the Allan Variance low pass filter frequency response isnt 
necessarily rectangular as assumed in the above formula.

Bruce



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