Hi Attila, Very interesting, thanks. I found ref (2) by seems that need to pay or be to registered as a researcher to get ref (1). Is there a easier way to get a copy ? Thx, Gilles.
> Le 15 sept. 2018 à 12:26, Attila Kinali <att...@kinali.ch> a écrit : > > On Fri, 14 Sep 2018 21:42:05 +0000 > Bryan _ <bpl...@outlook.com> wrote: > >> I would be interested in hearing more of the more suitable classes of >> logic chips. I have a 20Mhz rubidium that I wanted to divide down to 10Mhz > > Any logic family works, as long as it is fast enough to handle your > input frequency. Due to the non-linear (aka digital) behaviour > of a D-Flipflop style divider, it is recommended to use the slowest > possible logic family for the task. Otherwise the harmonics of the > switching of the FF will down-mix high frequency white noise down > to the signal band (this is the reason for the 10*log(N) noise scaling > of digital divider that Egan[1] and Calosso/Rubiola[2] and a few others > mentioned). > > As a rule of thumb, I'd say that the FF should not be more than 10 to 20 > times faster than the input frequency, to limit noise down-mixing. > If your FF is too fast or you want to reduce the noise floor, capacitively > loading and/or having some additional resistance in the Vcc and GND lines > will help slow it down. But ensure that the resistance is still low enough > that the FF's supply stays within specs at all time. Similarly, the > capacitive loading should be low enough that the output current is within > reasonable bounds. > > Alternatively, using the Λ-divider approach[2] and introducing voltage > steps between 0 and 1 will also reduce down-mixing. > > If you divide by something that is not a power of 2, then it is important > that each stage produces an output waveform with a 50% duty cycle. Otherwise > flicker noise which has been up-mixed by a previous stage, will be down-mixed > into the signal band, increasing the close-in phase-noise. > > > Attila Kinali > > [1] "Modeling Phase Noise in Frequency Dividers," by Egan, 1990 > > [2] "The Sampling Theorem in Pi and Lambda Digital Frequency Dividers," > by Calosso and Rubiola 2013 > > -- > <JaberWorky> The bad part of Zurich is where the degenerates > throw DARK chocolate at you. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.