Yes, it can be done based on a PPS only timing. You must design a PI (maybe PID) regulator: the EFC must stay steady when the phase difference between the two PPSes is zero (integral action). Then you must move the EFC (when there is a difference) proportionally with the difference itself and only a small part of the difference drives the integrator to increment/decrement the new steady EFC level. When the difference is again zero the proportinal part is gone and remains the small amount of correction for the integral part. There is a gain for the integral action (samll) and a gain for the porportional action (should be large, but to be evaluated).
On Fri, Dec 30, 2011 at 6:26 PM, Chris Albertson <[email protected]>wrote: > On Thu, Dec 29, 2011 at 8:24 PM, Mark Spencer <[email protected]> > wrote: > > One of the designs using the 10 kHz output from a Jupiter gps engine and > a simple PLL to discipline an ocxo might be good starting point if suitable > gps engines are still available. There won't be much to tweak but the > performance could be quite good. > > I just finished reading about that one. It requires no longer > available GPS reciever. Maybe I should r-phrase the question: > > "What is the simplest design for a GPSDO that uses only the PPS signal > from a modern GPS?" > > Half of the reason for the question is academic. Then if a simple > enough design presented itself it would be fun to try it. > > The simplest design I can think of now is based on a flip-flop. The > PPS "sets' the FF and the next raising edge of the local oscillator > "resets" it. (The local oscillator might need to be divided down or > a slower 1Mhz oscillator used so the FF remains "on" for a reasonable > time.) > > Next the FF gates a current source to a capacitor. The voltage in > the cap is amplified and controls the local oscillator frequency via a > low pas filter. Likely the "low pass filter" would be an active > device that we call an "integrator" > > You need to discharge the cap for the next cycle. One could rig a > one-shoot timer to discharge the cap. Actually there are about four > states that need to be cycled every second. > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > 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.
