Hi > On Oct 4, 2017, at 12:49 PM, Attila Kinali <[email protected]> wrote: > > On Wed, 4 Oct 2017 11:01:31 -0400 > Bob kb8tq <[email protected]> wrote: > >> This gets into the “other side” of the whole comparator / squaring circuit >> test process. What matters for ADEV and what matters for phase noise at >> 100KHz offset likely are not the same thing. A lot of circuits do quite well >> inside 100 Hz, but not so well above that offset. > > Yes. Definitely something one should consider. > > For completeness: > > * For cycle-to-cycle jitter what matters is the white noise floor. > Ie everything above 100Hz-1kHz, as this is the largest contributor > of "short" tau jitter. This is the component that limits e.g. the > single shot resolution of time-interval counters. > > * For ADEV/TDEV at "long" taus >1-100s what matters is the close-in, 1/f^a, > flicker noise. As white noise averages out with sqrt(n), with n > being the number of samples taken, but 1/f^a noise does not. > > When the transistion to from short to long taus happens depends as much > on the noise as on the rate of measurement. If we measure a 1PPS, the > the ADEV at tau=1s will be dominated by white noise and at tau=10s it > could be still a significant portion of the noise seen. On the other > hand, if we measure a 1kHz signal (at that rate), the tau=1s will be > (most likely) dominated by the flicker noise. > > >> Driving a 5V powered CMOS gate with 5.5V p-p does a pretty good job …. > > If you have this much signal, yes. Not everyone has the luxury of an > steady +19dBm input signal. Part of the reason why I am looking into > this is because I wanted a squaring circuit that can work down to +2dBm, > where, so I have been told, CMOS gates do not work well anymore. >
You don’t need 19 DBM to put 5.5V into a gate. A broadband transformer or a matching network and 0 DBM will do just fine. Neither one is terribly hard to come by. Neither one takes up much board space. Bob > > Attila Kinali > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > _______________________________________________ > 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.
