What about the application and the trigger circuit In a message dated 9/15/2018 6:27:50 AM Eastern Standard Time, [email protected] writes:
On Fri, 14 Sep 2018 21:42:05 +0000 Bryan _ <[email protected]> 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 -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
