How many samples of the Loran input signal in that 1/6th of the period? On Wed, Oct 10, 2018 at 5:22 PM Poul-Henning Kamp <[email protected]> wrote: > > -------- > In message <[email protected]>, Attila Kinali > w > rites: > > >> >"A Physical Sine-to-Square Converter Noise Model," > >> > by Kinali, 2018 > >> > >[...] > >Hence the first gain stage already aliases the noise from its whole > >bandwidth, which can be a lot of noise if the BW is large. > > Some years ago I spent a lot of time trying to find a way to > "oversample" single-shots of the 3rd zero-crossing of Loran-C > signals. > > My finding was that of all the technologies available, the simple > comparator was the worst, because it only "looks" at a very tiny > time-slice around the actual zero-crossing, and thus is needlessly > sensitive to noise. > > To make matters worse, the window is always late, it cannot be > symmetric, because at least some electrons have to move in the > opposite direction before the comparator changes state. HP has > interesting info about this in an old app-note on TI counters. > > If the incoming curve-shape is unknown, that is the only thing one > can do, but when the curve-shape is known to be a sine or a loran-C, > better results can be had with a wider time window. > > The final version of my code (This was SDR with an ADC directly on > the antenna) found the optimal least-square match between the sampled > signal and the theoretical signal for a configurable time-window, > produced the zero crossing from the theoretical signal. > > Best performance was around 1/6-th period, which I'm sure there was > a reason for, but I gave up looking for it. > > I have not found a way to implement it in the analog domain. > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [email protected] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > > _______________________________________________ > 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.
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