[time-nuts] ensemble oscillators for better stability
Tom Van Baak
tvb at LeapSecond.com
Sun Dec 30 04:16:32 UTC 2012
>> 1) This was a topic some years back -- for internal use, hp tightly
>> combined multiple 10811 oscillators so that the net phase noise or
>> short-term performance was significantly better than any one of the
>> constituent oscillators.
> Care to share a reference on that? It would be interesting to see how
> they did it and how well they where doing it.
Yes, it came up in a long thread called "GPS noise reduction" back in April 2008. I'll mention it again -- when I visited the HP facility in Santa Clara years ago I saw or was told about a special low noise 10 MHz reference that was used to measure the phase noise of shipping 10811 oscillators. The reference itself was a set of several hand-picked 10811's that were combined in some clever way so that they all steered themselves creating a coherent single output with significantly lower noise than any one individual 10811. I don't have further details but assume the RF and PLL experts here on the list can figure out what is meant by this and propose a paper design. It was probably more than 2 oscillators, but I don't remember now if it was 3 or 6 or more. Rick Karlquist may also know about this system; either when/how it was built or what level of performance it delivered.
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