Hi In general the way you go from 1 to 10 to 100 seconds is to decimate ( = throw away) the data to get a phase record at the tau you are after. Any averaging that you do will filter out some noise. Since ADEV is a measure of noise, getting rid of it is not a real good idea. You can indeed make your results look *very* good by doing this. What those results would actually represent …. who knows ….
Bob > On May 2, 2020, at 8:24 AM, Simon Lewis <[email protected]> wrote: > > Hi all, > > I have a fairly newbie question on averaging of phase data, prior to ADEV. > > In a paper by Sherman and Jordens (https://arxiv.org/pdf/1605.03505.pdf) on > oscillator metrology using SDR (Ettus N210), for long term measurements (1 > tau up) the group estimates an average phase to reduce the data volume. > They use both a novel lower-bound variance estimate, and what I assume was > a rectangular average of N samples per second (original data rate was > 1Msamples/s). Both apparently provided similar results. > > From what I've read/tried to understand, pre-averaging phase isn't > practically a good idea, considering the ADEV natively does this, and you > end up with a lower estimate than reality. They state that time interval > counters effectively do this for frequency measurements. > > I know that one can do this with caveats, and in essence this is what MDEV > does (I believe?), but is it not more 'real' to just downsample the phase > data? That is, drop N-1 samples per second (not decimating which would > filter the higher order components), and then ADEV the downsampled data. > I'm sure I'm missing some understanding here! > > Thanks, > Simon > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
