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praneethbobba

Member

Registered: 2013-10-06

Posts: 5

Need help in Calculating Power from Power Spectral Density ?

Hi All

While calculating power from power spectral density , we generally integrate it over the entire range (infinity) of frequencies as the equation suggests. But in some calculations we take only the positive half of frequencies to calculate power even though the PSD occupies entire positive and negative range of frequencies (eg. two sided noise spectrum).

Can you please explain when when should we consider only + frequencies and when should we consider both + and - frequencies ?? Any special cases in such considerations ??

Thanks in advance
Praneeth

Nehushtan

Member

Registered: 2013-03-09

Posts: 957

Re: Need help in Calculating Power from Power Spectral Density ?

This is what I’ve found:

http://en.wikipedia.org/wiki/Spectral_d … al_density

The power of the signal in a given frequency band

can be calculated by integrating over positive and negative frequencies

where

is the power spectral density. This may be complex-valued. However the spectrum of a real-valued process is an even function of frequency:

. Hence for real-valued processes you only need to integrate over the positive frequencies and multiply by 2.

This is not exactly my area of expertise but it’s what I’ve made out from reading the Wikipedia page. Hope I’m making sense.

Last edited by Nehushtan (2013-11-05 01:15:49)

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