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

Grant Hodgson grant at ghengineering.co.uk
Tue Dec 16 10:05:24 UTC 2008


Brian

Could you give some more details?  I think alternative solutions to 
MMICs at 5 and 10MHz would give much lower phase noise.

Bruce's web pages have a number of designs that will get the 5MHz 
reference up to 20MHz in 2 stages :-

http://www.ko4bb.com/~bruce/FrequencyMultipliers.html

Another approach would be to use op-amps instead of MMICs, op-amps with 
a low flicker corner frequency should give lower close in noise than a 
MMIC, but probably won't be as good as a discrete solution.

regards

Grant

> 	
> 
> 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




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