Hi Interesting question ….
> On Aug 29, 2015, at 5:24 AM, Neville Michie <[email protected]> wrote: > > > A PLL locks on to the nearest cycle, > is a Time Locked Loop different? At the most basic level, no. Phase is already commonly looked at in units of time. Yes that’s a bit odd at first. ADEV (for example) is a phase based measure that uses units of time. > If the decoded time from a GPS system is used discipline > an oscillator then leap seconds would have to have > a frequency transient to maintain lock. Which creates all sorts of issues in the loop. GPS time rather than UTC (with leap seconds ) is used in every GPSDO system I’ve seen for this reason. > If you use the output to say drive a radio telescope monitoring > a distant object you would want Earth’s rotation to be phase or > sidereal Time locked. I realise that for such a task far more complex > computation would be required. > So is a time locked loop a valid concept? Because you *always* get into application specific details, sure. As a more general concept: Time locked loop -> has a static time error in a gain only loop. In your example of leap seconds, that’s going to require something a bit different than a classic PLL. In the non-leap second case (GPS time) it’s effectively what is done in a GPSDO. There it is commonly referred to as phase lock. Since some of the details there are a bit weird, maybe a new term is called for. Bob > > Cheers, > Neville Michie > _______________________________________________ > 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.
