Hi There are many ways to implement just about anything. There are lots of features that can be added into any design. Multi-lock loops are something that goes back at least into the 1940’s.
> On Aug 28, 2015, at 6:37 PM, Azelio Boriani <[email protected]> wrote: > > If FLL: something that links frequencies, > PLL: something that links phases, > frequency detector: output proportional to frequency error, > phase detector: output proportional to phase error (XOR), > and the original question (about FLL) was how to implement a simple FLL, > can an FLL be made by a phase detector? No it can not with a real phase detector. The advantage of an FLL is that it can tolerate a frequency error and still be locked. That’s it’s advantage. If you have a phase detector, it will run into a limit and crash with a frequency error. If you have a system that needs tolerate a long term frequency offset, that’s one of many reasons to use an FLL. > Can a PLL be made by a > frequency detector? Again, not with a real world part. Any real detector will have a zero error. That error will be fatal if you are trying to do phase with a frequency detector. Bob > Phase_detector_XOR + RC + VCO-> FLL: equal frequencies, phase linked > to VCO odds, > in this case the frequency error is 0. > > On Fri, Aug 28, 2015 at 7:14 PM, Charles Steinmetz > <[email protected]> wrote: >> Azelio wrote: >> >>> OK: the XOR gate with an RC is a defective PLL and a defective FLL. It >>> is a simple way to have an idea of what an xLL should be but of no >>> serious use. >> >> >> No, not at all. I was suggesting that the XOR PLL you were commenting on >> had problems. >> >> First, an XOR with or without an RC is not an FLL at all, of any sort. >> Second, the XOR gate is a time-honored phase detector for PLLs, and if its >> limitations are understood and accounted for, it makes a perfectly >> serviceable PD for a PLL. There are other phase detectors that are more >> popular these days, for a variety of reasons, but the XOR works just fine in >> a proper design. >> >> See, e.g.: >> Best, Phase-Locked Loops (2007), pp. 16-18 >> Gardner, Phaselock Techniques (3rd ed) (2005), pp. 245-46 >> Wolaver, Phase-Locked Loop Circuit Design (1991) pp. 55-59 >> <https://en.wikipedia.org/wiki/Phase_detector> >> <https://jaunty-electronics.com/blog/2012/09/exclusive-or-xor-gate-based-phase-detector/> >> <http://memo.cgu.edu.tw/jtkuo/files/eelab%202014(iii)/1230_lab12_expxx_phaselockedloop.pdf> >> and many, many, many others. >> >> >> Best regards, >> >> Charles >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
