In my opinion you fall in the case of disciplining with holdover... this is more like a disciplined oscillator (like a GPSDO) problem than a PLL.
On Wed, Sep 19, 2012 at 1:45 AM, Jim Lux <[email protected]> wrote: > On 9/18/12 9:48 AM, Raj wrote: > >> If you break the DC control chain of the PLL with a A2D and a controller >> and back with a D2A .. you would program the control with any kind of >> behavior you want. Just a thought! >> >> That is exactly what we do... the PLL is actually implemented digitally > (DAC driving the VCO).. > > But what I'm looking for is a theoretical treatment of the output > statistics (Allan Dev, mostly) in terms of the interrupted reference input. > > For context.. we do precision ranging of spacecraft in deep space by > sending a hydrogen maser derived signal TO the spacecraft which locks a > local VCXO to that signal, and then uses the VCXO to generate a return > signal with a constant ratio (e.g. 880/741) to the input. > > By measuring the time it takes for the round trip (essentially counting > phase cycles on the return signal (against our hydrogen maser, again), we > measure Range and Doppler, which is then used to determine the position of > the spacecraft. > > Typical performance is sub-meter and sub cm/sec. (A very high performance > would be that the transponder adds 4E-15 Allan Dev over 1000 sec... 1E-11 > or 1E-12 over 10-100 secs is more usual) > > What we want to know is "what happens if the receiver and transmitter > can't run at the same time"? Obviously, we have less information coming > into the system (we see the uplink half the time, so right there, we have a > 2:1 hit) and the ground end only sees the transmit signal half the time > (another 2:1 hit), so, from an information theory standpoint we've already > put ourselves in a hole, but, what does the statistics really look like for > the turnaround loop.. > > Full Duplex full power turnaround is expensive in power, mass, etc. (for > instance, you have to have good filters to make sure that your receiver > isn't corrupted by the transmitter) > > > > > ______________________________**_________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<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.
