John,
On 08/31/2015 12:37 AM, John Miles wrote:
The is a publication by the NPL that talks about a similar technique, but
comes to a somewhat different conclusion.
http://publications.npl.co.uk/npl_web/pdf/mgpg68.pdf
Bottom line: it holds that the phase noise of all three sources can be
determined if they are taken two at a time; one as ref and the other as
the DUT.
Yes, that's the three-cornered hat technique. The document is a bit dated in
that respect -- it was published in 2004, just as Timing Solutions was starting
to work on cross-correlated direct digital measurements.
The dual-reference method always converges on the DUT noise if set up properly,
but it doesn't give you any insight into the two independent sources being used
as references. You have to swap the DUT with each of the references and repeat
the measurement if you want to characterize all three sources, while the
N-cornered hat returns separated variances for all sources at once (at least
ideally.)
Indeed.
On that note, did you look more closely on the NIST analysis of
cross-correlation and a possible cancellation and thus overly optimistic
results? Did it have any consequence on your code? What did you take
away from it?
Cheers,
Magnus
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