Getting down to the nitty-gritty about noise and it's effect on IQ Locked

Started Apr 15, 2010 | Discussions thread
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Joofa Senior Member • Posts: 2,655
Re: Total noise power

pocketfulladoubles wrote:

I'm losing you, but I could be wrong. Just as a thought experiment, say you have some PSD function with 1 unit of some arbitrary resolution. Now take your 2x2 pixel per original pixel increase in resolution, basically you now have four times the pixels, and each pixel has 1/4 the noise power. Each bin of your FFT is now 1/4 the bandwidth, but you also have four times the probability per bin, so you're right back where you started. Hencse, the PSD has not changed. It is a density, not an absolute.

PSD is the Fourier transform of the autocorrelation function. Under the white noise assumption, the autocorrelation for lower MP is N*delta(t) and for higher MP it is N/4*delta(t). Now you can take the Fourier transform and see that the PSDs are different.

It also isn't useful for non-random signals, which I'm still not sure is completely the case.

The concept of PSD is perfectly valid for non-random or deterministic signals.


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Dj Joofa

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