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# Discussion Groups | Comp.DSP | Autocorrelation versus Cross-correlation

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# Autocorrelation versus Cross-correlation - Tao - 2007-03-14 06:29:00

Hello,

I am trying to determine the frequency of a signal. Samples of the signal
are taken from 2 channels at a time. After some filtering, I perform the
autocorrelation of each channel, and the cross-correlation of the 2
channels.

The autocorrelations, as expected, yield almost identical results, from
which we can easily work out the frequency of the measured signal.
However, the cross-correlation gives a frequency that slightly differs
from that given by the autocorrelation.

I am inclined to give preference to the cross-correlation results, since,
as far as my understanding goes, correlating independent channels takes
advantage of the information contained in each of them, and thus yields
better results in terms of low noise and accuracy.

Which one should I believe? Autocorrelation or cross-correlation?

Tao

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# Re: Autocorrelation versus Cross-correlation - 2007-03-14 08:40:00

On Mar 14, 6:29 am, "Tao" <taorom...@hotmail.com> wrote:
> Hello,
>
> I am trying to determine the frequency of a signal. Samples of the signal
> are taken from 2 channels at a time. After some filtering, I perform the
> autocorrelation of each channel, and the cross-correlation of the 2
> channels.
>
> The autocorrelations, as expected, yield almost identical results, from
> which we can easily work out the frequency of the measured signal.
> However, the cross-correlation gives a frequency that slightly differs
> from that given by the autocorrelation.
>
> I am inclined to give preference to the cross-correlation results, since,
> as far as my understanding goes, correlating independent channels takes
> advantage of the information contained in each of them, and thus yields
> better results in terms of low noise and accuracy.
>
> Which one should I believe? Autocorrelation or cross-correlation?
>
> Tao

Are the two sample clocks the same?

John

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# Re: Autocorrelation versus Cross-correlation - Tao - 2007-03-14 22:04:00

Hello John,

Yes, they are run by the same clock.

Tao
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