[time-nuts] Determining Allan Deviation From Interpolated Peak Frequency Readings

[Attila Kinali]

On Fri, 15 Dec 2017 10:08:29 -0700
Mark Goldberg <marklgoldberg at gmail.com> wrote:

> > The approach using FFT works, but just using the peak frequency, you throw
> > away half of the data (the phase) and also limit yourself in precision
> > to the bin width. It's not 100% clear that estimating the frequency
> > using an FFT is unbiased in this case, thus you might get worse (or better)
> > results than what the oscillator actually does.
> >
> 
> Since I do not know the exact algorithm used to interpolate peak frequency,
> I don't know the effect on precision. They do claim that the peak frequency
> determination precision is much smaller than the bin width, which seems to
> be shown by the data.
> 
> The results are good enough to discern between "bad" and "good" units under
> test, but I have no way to compare my results to any other method of
> measurement. This is all I have access to.

If all you want is to discern good and bad units, this is good enough.
 
> > [1] "Oscillator metrology with software defined radio",
> > by Sherman and Jördens, 2016
> > https://arxiv.org/abs/1605.03505
> >
> 
> I have seen this paper before. Unfortunately, it is a lot more work to
> implement than what I have already done. I am really a hardware engineer,
> with decades old education in control systems that has not been used in a
> long time. It would take getting my brain back in gear and re-studying, not
> a bad thing actually!
> 
> The other issue is the Perseus drivers have issues under Windows 10 that
> may or may not be solved. I was able to get it to work with Spectrum Lab,
> but it does not work with many other tools that would be able to implement
> this algorithm.
> 
> That said, I may look into it further in the future.

Apparently the Perseus is supported by GnuRadio[1]. Which means you can
just click your control system together (similar to LabView). According
to [2] the driver uses libusb and works on windows as well.

If you want to use GnuRadio, I suggest you go to one of the many Hackfests[3]
they have and let them jump-start you (I started this way years ago).


				Attila Kinali


[1] https://gnuradio.org/
[2] https://github.com/Microtelecom/libperseus-sdr
[3] https://www.gnuradio.org/event-type/hackfest/


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