Re: [Discuss-gnuradio] Handling of IQ files

[Henry Barton]

So correlating is digitally mixing something with a predetermined sequence? I’ve been struggling to figure out what correlation means and this seems right. I guess, then, if you have a PSK waveform you might multiply it by something, starting at various offsets in the signal, to try and decode it?

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From: madengr
Sent: ‎Sunday‎, ‎March‎ ‎20‎, ‎2016 ‎12‎:‎22‎ ‎PM
To: address@hidden

Yes, pretty much.  With the DFT (and the continuous one) you are correlating
the input waveform with harmonically related, complex sinusoids; essentially
for each harmonic you mix it down to DC then sum (integrate).  The FFT is
different (I actually don't know how it works, other than it operates on 2^n
samples), but the output is the same.
Lou


Henry Barton wrote
> I’ve read up on the FFT and DSP and I must say I’m impressed that
> multiplying two waveforms is the digital equivalent of heterodyning. Am I
> right in my understanding that finding frequency components (FFT-ing) is
> simply multiplying a series of known sine waves by your input waveform?





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