[time-nuts] Phase noise at 1-100Hz

[Javier Herrero]

El 07/04/2011 10:49, Bruce Griffiths escribió:
>
> The 5372A or 5370A will only suffice if the phase noise is 
> sufficiently high.
> They are likely to be too noisy by several orders of magnitude for a 
> good crystal oscillator.
> However they may suffice for something like a noisy ring oscillator or 
> even a low Q LC oscillator.
> There's also the question of defining the bandwidth so as to avoid 
> folding high frequency phase noise into the measurement when the phase 
> sampling rate is relatively low as it will likely be with a 5370A..
>
Thanks, Bruce, it is something that I was suspecting... both the 
inherent counter noise and the aliasing of higher frequency phase noise. 
I would expect that the aliasing would not be very problematic, since 
phase noise for this oscillator seems to be quite low over 100Hz, at 
least with respect to the requirements I've.

My limits are -25dBc/Hz @ 1Hz, -54dBc/Hz @ 10Hz and -75dBc/Hz @ 100Hz, 
and really I don't need to measure the exact phase noise at this range, 
only to test that it is below the limits. Any experience of what would 
be the measurement limits to be expected with a 5372A?

At higher frequencies, I've done some preliminary test with an 8566B and 
John Miles phase noise plotting software, and I'm quite comfortably 
inside specs (both measured noise and measurement limit of the 8566B).

Best regards,

Javier


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Javier Herrero                            EMAIL: jherrero at hvsistemas.com
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