Bruce- OK... So, linear operation does therefore seem to be the preferred way to operate these MMICs rather than operation into compression. That's what I seem to be observing if only because my final RF frequency is so high and RX bandwidth so low.
Having said that, if my frequency synthesis scheme involves a mixer does the same effect of low frequency noise to phase noise conversion still take place? After all, the mixer element is typically into compression if it's a FET based mixer. I assume a diode mixer is more immune to similar effects? I'm trying to grow my intuitive understanding of the subtle sources of noise. But I don't recall Maas giving much info on this topic in his otherwise excellent text. As always, thanks for your sagely advice. -Brian -----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Bruce Griffiths Sent: Monday, December 15, 2008 5:00 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Close-in phase noise question... [email protected] 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
