On Wed, 4 Oct 2017 11:01:31 -0400 Bob kb8tq <kb...@n1k.org> 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. 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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.