Sampling unsychronized signals with a DFF is problematic, since if setup and hold times are not met the output could oscillate and maybe settle to some noise driven value. I can't help thinking that if you are sampling the 10MHz signal at 1Hz the only way to get reasonable resolution is to sample the 10MHz sinewave signal's fastest part with tight analog sample & hold. Looking at the result wih a slow, low-cost 24-bit A to D chip would give tremendous resolution - if the drift was low enough. Use the ADC over a sub-range and add a small micro for noise filtering and averaging and one can achieve measurements result in the 10s of femtoseconds.
________________________________ From: David <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Sent: Fri, February 10, 2012 8:10:56 PM Subject: Re: [time-nuts] GPS lock of the FE5680. Current experiment and question All you need for this is the flip-flop. Clock the flip-flop with the 1 PPS signal and capture whether the oscillator is leading or lagging. This requires the 10 MHz oscillator to be within 1 Hz but if you divide it down before the comparison, you can extend this range as needed to handle wider initial oscillator frequencies and larger amounts of PPS jitter. The simple GPSDO design in QST a couple years ago did something like this. _______________________________________________ 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.
