Hi I’m sure there is a closed form solution somewhere out there that includes noise. It is more common to do it with simulation by one method or another. You normally have a lot going on in a PLL.
Simple answer is - less gain = less bandwidth. If what you have is too wide, cut it down. If you have too much of a peak with just P, check for lag in the circuit. It is very normal to have 3db of noise peaking. It’s generally best to run through a gain / stability calculation once you go to P-I. It will not help much with the noise side of things but it will help with getting the loop to lock. It will also give you a good idea of how much gain peaking you may have with a given configuration. There are a ton of app notes and text books out there on that side of it. Gardner: https://www.amazon.com/Phaselock-Techniques-Floyd-M-Gardner/dp/0471430633 <https://www.amazon.com/Phaselock-Techniques-Floyd-M-Gardner/dp/0471430633> is an oldie but goodie in this area. Bob > On Feb 1, 2019, at 1:11 PM, Anders Wallin <[email protected]> wrote: > > Hi all, is there are rule-of-thumb or simple paper/presentation of how to > choose PLL-gains? > > I have a phase-detector that gives out a slope of roughly 1 V/rad, followed > by an op-amp circuit with proportional, integral, and double-integral gains > summed into one voltage [0, 3.3V] on the tune-pine of the OCXO ( +/- 0.6 > ppm pull-range, from datasheet). > > So far it locks with only P-gain, but the phase-noise (and ADEV) shows a > 'bump' somewhere between 10 and 100 Hz offset from the carrier. > I tried the integrator with a time-constant of 1/16Hz using R 100k C 100n, > but it wouldn't lock. > The thinking was to put the integrator time-constant about where the > free-running ADEV turns upwards from a 1/tau slope. > > So far I didn't enable the double-integrator - not sure if it's worth the > trouble or not.. > > thanks, > Anders > _______________________________________________ > 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.
