Am 29.11.19 um 11:45 schrieb Jan-Derk Bakker:
In general: as much as I like having it in my toolbox, I don't see how
using an FFT would be the best tool for the job in a zero-crossing detector
for a DMTD, let alone this particular sampling DMTD. For one, this 8-bit
processor doesn't have the spare cycles to run FFTs on the 32-bit data I
get from my CIC^2 decimator; besides that, I would only be interested in a
single bin (the beat frequency), where it would be more efficient to simply
I/Q-demodulate the samples in software (O(N) vs O(N log N)). While I admit
that in the latter case windowing would help, at this point I/Q
demodulating (effectively calculating only a single bin of the DFT) does
not appear to have advantages over least squares fitting the arcsine of the
incoming samples. Am I missing something here?
I admit that I did not follow this thread closely, but the Goerzel filter
is the single output line DFT , with O(n).
<
https://www.mathworks.com/help/signal/ref/goertzel.html;jsessionid=8816f77eb76ad7dd1913c7021698
>
< https://en.wikipedia.org/wiki/Goertzel_algorithm >
If you need to simulate floats, fractional integers are easiest.
I/Q demodulation probably requires to recreate a clean carrier if you want
absolute phase and not only relative jumps. That sounds more like FPGA
than 8051, or whatever the 8 bit processor of the day may be.
regards, Gerhard
OK, in a previous life I did build a system for geophysics, where they fed
dangerous amounts of AC into the soil and measured the potential at
some 50 nodes. Rubber boots required.
Each node had a 8951 to control some switches and communicate setups.
They were most exited when I gave them the sources so they could
implement FFT pre-processing locally on each node themselves.
That required willingness to suffer.
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
