On 5 June 2010 19:07, Bruce Griffiths <[email protected]> wrote: > Wrong again.
No, I'm not wrong Bruce. > The integration/averaging referred to occurs when one counts the output > transitions of the VFC for a fixed time interval. > This process needs to be replicated using the sampled EFC data if one is to > measure ADEV. This process is exactly replicated by oversampling the EFC and determining the average for a fixed time period. If you can't see that this performs exactly the same function, I don't know what will convince you. Steve > Bruce > > Steve Rooke wrote: >> >> I think I have found the source of the "integration" issue. I've spent >> some considerable time ploughing through as many sources of >> descriptions on ADEV, AVAR and the tight-PLL method. I've even tried >> looking for the infamous "finite time interval integrator" which seems >> to be highly notable by it's complete absence on Google. Well, >> eventually the answer struck me directly in the eye, the source of the >> integrate issue comes directly down to the original paper that Warren >> posted a link for:- >> >> D. Tight phase lock loop method >> >> The second type of phase lock loop method (shown in figure 1.7) is >> essentially the same as the first in figure 1.6 except that in this >> case the loop is in a tight phase lock condition; i.e., the response >> time of the loop is much shorter than the sample times of >> interest--typically a few milliseconds. In such a case, the phase >> fluctuations are being integrated so that the voltage output is >> proportional to the frequency fluctuations between the two oscillators >> and is no longer proportional to the phase fluctuations (for sample >> times longer than the response time of the loop). A bias box is used >> to adjust the voltage on the varicap to a tuning point that is fairly >> linear and of a reasonable value. The voltage fluctuations prior to >> the bias box (biased slightly away from zero) may be fed to a voltage >> to frequency converter which in turn is fed to a frequency counter >> where one may read out the frequency fluctuations with great >> amplification of the instabilities between this pair of oscillators. >> The frequency counter data are logged with a data logging device. The >> coefficient of the varicap and the coefficient of the voltage to >> frequency converter are used to determine the fractional frequency >> fluctuations, yi, between the oscillators, where i denotes the ith >> measurement as shown in figure 1.7. It is not difficult to achieve a >> sensitivity of a part in 1014 per Hz resolution of the frequency >> counter, so one has excellent precision capabilities with this system. >> >> http://tf.nist.gov/phase/Properties/one.htm >> >> The relevant section here is "the response time of the loop is much >> shorter than the sample times of interest--typically a few >> milliseconds. In such a case, the phase fluctuations are being >> integrated so that the voltage output is proportional to the frequency >> fluctuations". So what this says is that by incorporating a PLL-loop >> filter that has a B/W much wider than the sample time, the phase >> fluctuations are integrated into the reference oscillator such that >> the control voltage of the tight-PLL now reads frequency which is >> unlike the loose-PLL which directly records the phase relationship >> between the oscillators. So the term "integrated" here is used a verb >> and not a noun, therefore it is an intrinsic function of the design >> not a separate process. >> >> Steve >> -- >> Steve Rooke - ZL3TUV& G8KVD >> The only reason for time is so that everything doesn't happen at once. >> - Einstein >> >> _______________________________________________ >> 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. > -- Steve Rooke - ZL3TUV & G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein _______________________________________________ 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.
