Quartzlock makes a couple of interesting digital PLL-modules, marketed specifically as ultra low noise cleanup loops. The datasheets contain a lot of interesting and useful information about the software architecture - not enough that *I* can recreate it, but perhaps someone more skilled than me can.
Very interesting stuff: http://quartzlock.com/product/timing-modules/digital-phase-lock-loop Does anyone know of a reference where more information about this approach can be found? I am impressed they can do all that in a PIC 16F689.. On Sat, Oct 17, 2015 at 4:48 PM, Jim Lux <jim...@earthlink.net> wrote: > On 10/17/15 6:17 AM, Alex Pummer wrote: > >> >> actually, that is a ketch 22, if the loop bandwidth is to low, you will >> have low noise , but it may will not lock at all, an other way to try to >> filter out the noise, also you may make the loop filter digital, but >> leave the the PLL analog, that could have the possibility to have the >> advantage to be able to change the loop bandwidth increase for locking, >> and reduce after the detected locking >> > > changing loop bandwidth between acquisition and tracking, or, similarly, > (effective) loop bandwidth that changes with SNR are pretty common > strategies. > > In the deep space transponder world (where you are acquiring and tracking > a very narrow carrier at -155 or -160 dBm against noise of -170dBm/Hz) you > also want to know what order filter you should be using in the tracking > loop. If there's an expectation that the frequency being tracked is > changing (e.g. Doppler), then a low order loop may not be the best choice. > > > > > _______________________________________________ > 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. > _______________________________________________ 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.