Ok. I understand now what you suggest. Thanks for the explanation. Luis Cupido. ct1dmk.
Bruce Griffiths wrote: > Luis Cupido wrote: >> Bruce, >> >> > No analog filtering of the D flipflop output is required. >> >> Now you got me lost. >> >> We were talking about a GPSDO, that is locking >> an VCXO on the GPS time (1pps or else) >> So by the end of it you need an analog >> signal to control the voltage input of the VCXO. Right ? >> >> Where you get that from ? >> If not by filtering your flip-flop output >> what else you have in between the 1pps and the VCXO ? >> CPU's DAC's ???? >> > Some software, including a sigma delta DAC, the effect of which is no > different, in principle, than the filtering etc required by any of your > phase detector implementations. > The 1 bit phase error samples are processed in software (or hardware > depending on one's inclinations, expertise, etc) in a similar way that > samples from an N (>1) phase detector samples are, to produce a digital > output for a DAC which drives the OCXO EFC input. The only difference is > that a sigma delta DAC is used instead of a conventional DAC. > >> if so how does your complexity arguments still apply ? >> >> >> > The interpretation of "complexity " depends on ones background and > experience. > The originator of the thread indicated that they had some microprocessor > software experience. >> Luis Cupido >> > I was trying to tailor the design to the stated strengths of the > originator of the thread. > > If one is trying to "squeeze" the ultimate in performance when using a > GPS receiver to discipline an OCXO, then carrier phase measurements > potentially offer much higher performance than can be achieved by using > the PPS output of a typical GPS timing receiver. > However only a few commercially available GPS receivers are suitable for > this application. > The GPS receiver oscillators all have to be phase locked to the OCXO > being disciplined. > This approach has been used in at least one commercially available GPSDOCXO. > In principle a GPS receiver has all the required measurement hardware, > so all that is required are suitable algorithms implemented in either > software running on a DSP, microprocessor, etc, or implemented in > hardware (CPLD etc). > > Bruce > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
