[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[ghf at hoffmann-hochfrequenz.de]

Am 2022-04-05 22:09, schrieb Mike Monett:
> Joseph,
> 
> You will find it difficult to get below -170 dBc/Hz. However, you can 
> use
> cross-correlation to get as low as -220 dBc/Hz.

Yes, it is not impossible to get these numbers. But it is cheaper to 
throw dice.

U.Rohde is 30 dB more modest:

"...amplifier certainly has a higher noise figure, as it is driven with 
more power and there is no
improvement possible. There is an optimum condition and some of the 
measurements showing
‐190dBc/Hz do not seem to match the theoretical calculations. The 
correlation allows us to look
below KT, but the noise contribution below KT is as useful as finding 
one gold atom in your body’s
blood. This gold atom has no contribution to your system."

taken from the conclusion of "Phase Noise Measurements and its 
Limitations – Sent to MWJ – for publication in April 2013 issue"

Gerhard




> 
> Rubiola is a wealth of information on cross-correlation. You can 
> download
> his papers at
> 
>   http://rubiola.org/index.html
> 
> See "The cross-spectrum experimental method, February 2010"
> 
> See also measurements by John Ackerman:
> 
>   http://www.febo.com/pages/cross-correlation/
> 
> MRM
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