Didier Juges wrote: > > > >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] On Behalf Of Bruce Griffiths >> Sent: Sunday, May 04, 2008 7:27 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Fast frequency counting question >> >> John Miles wrote: >> >>> If you go nuts with sampling >>> precision, aren't you just going to get more information than the >>> underlying process is capable of generating? (I'm probably not >>> phrasing that very well, but you get the idea, hopefully.) >>> >>> >>> >> No, the device is an oscillator, everything of interest can >> be obtained from the times at which zero crossings occur. >> In effect one is measuring the phase deviations of the >> oscillator during startup. >> With a suitable measurement bandwidth, a measurement system >> noise of a few tens of femtosec or less is possible. >> In most cases the oscillator zero crossing jitter will be >> somewhat larger. >> The real problem lies in verifying the measurement system noise level. >> >> All one is attempting is to extend the phase noise >> measurement range down to averaging times of a few tens of microsec. >> >> Bruce >> >> >> > > I think the potential problem John is pointing out is that if the > performance down to that level is driven by process variations rather than > by circuit design (and therefore assumed to be randomly variable from unit > to unit), how useful is it going to be to measure the heck out of one or a > few unit if you cannot statistically extrapolate the results to the entire > population and be able to predict yield? > > Didier KO4BB > > Didier
To come to valid conclusions on that, one needs to develop a model for the effect and calibrate it against the process variables etc. Its always possible that previos models had similar effects bu it hadn't been noticed. 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.
