From: Dr Bruce Griffiths <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Ultra low phase noise floor measurement system for RF devices. Date: Sun, 01 Apr 2007 16:30:31 +1200 Message-ID: <[EMAIL PROTECTED]>
> Magnus Danielson wrote: > > In the article that was recently referred to, it was not a measurement rig > > for > > oscillators but for transfer components, such as gain-stages, phase shifters > > etc. and the approach is different then, since you do have the signal prior > > to > > being dirtyfied. Thus, the interferometer approach makes sense. The > > refinement > > was certainly interesting. > > > > Cheers, > > Magnus > > > Hej Magnus > > What about a 3 source version of the following with the oscillator under > test common to both channels together with using the cross spectrum to > isolate the noise due to the oscillator under test. (of course phase > locking the 2 other oscillators to the reference using a very low > bandwidth loop may also be required). Naturally Now, this would indeed improve the 1/f noise measurement floor of a cross- correlator setup, but for a fairly low price (thr addition of two hybrid couplers. It is really clever in its simplicity, since what you want to measure goes in arm A (non-flickered amplification) and what you demodulate with goes in arm B (flickered amplification - but won't demodulate unless you have _strong_ sidebands and then this technique is of no interest anyway - a spectrum analyzer does the job then). My concerns is rather about the hybrid coupler and frequency range. This work was on 9.9 GHz but what if I would like a more moderate frequency but a wider range (1 MHz to 1 GHz or so)? Ah well, this comment only discloses that I don't mess around enought in analog RF too much. I've learned a few new usefull things from the recent discussion on Rubiola (hey! Welcome!) papers! This little two-pagers should have come first up thought, since it in its simplicity contains one of the basic ideas which the more elaborate papers builds upon. Cheers, Magnus _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
