On 05/07/2012 10:59 PM, Azelio Boriani wrote:
Yes, interesting, now I realize... but:
the larger the deviation becomes and lower frequency it will have... and
both makes it>harder to suppress by filtering.
Filtering at what level? Lengthen the sampling time? The average build up?
That is, now I'm not aware and think that I have to correct as slowly as
possible because I think that the oscillator has to be disturbed to a
minimum. Then I see low frequency large deviations, so I think, OK, I have
to average longer to account for. Is this the filtering you are referring
to? So that one ends up increasing the slowness of the system getting only
very slow frequency very large deviations.
Thanks for the help
If you have a little frequency error the longer you wait to do any
adjustment the larger phase-deviation that frequency error will result
in. If you sample to seldom, then you rely on your DAC resolution and
stability inbetween your samples, the clock will essentially be in
hold-over. If this is 1 ms, 1 s or 1000 s will make a difference.
That relates to sampling rate, which puts a limit to the loop bandwidth
you can have.
But my main reaction was to the sample-rate vs. measure and adjust rate
(i.e. sample rate), and I wanted to point out that there is a merit in
sampling (much) faster. The modulation waveform is only to illustrate
the averaging behaviour.
Cheers,
Magnus
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