[time-nuts] Close-in phase noise question...

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Dec 15 21:59:31 UTC 2008


wa1zms at att.net wrote:
> Looking for comment here...
>
> The background:
> I'm working on a sub mm-wave LO chain for
> a ham radio application. While chasing issues
> of close-in phase (ie: within 1KHz of RF
> carrier) by peeling the "layers of the onion",
> I'm starting to question the performance of
> the MMICs that are used as buffers and amps
> following my Wenzel reference OCXOs.
>
> Question(s):
> Should any MMIC be allowed to be driven
> close to compression or into compression
> when striving for best close-in noise?
>
> I know and have seen the NF of a MMIC
> degrade while in compression, but my
> target right now is close-in noise rather
> than broadband noise.
>
> My design, in summary, takes 5MHz up to 630GHz
> via several multipliers and PLL stages.
>
> -Brian
>   
Brian

The increased nonlinearity when driven into compression will enhance the
conversion of low frequency noise to phase noise.

Bruce




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