cross power

[celynn]

Hi can anyone advise me how to create the cross spectral density in Labview.

[CoastalMaineBird]

I posted some info here

[celynn]

Hi, Thanks for your reply. I have read through it.

1.I am looking for the cross power density which is in the normalised form as the PSD.

Do you think i can create the CSD by using the cross power divide by the frequency resolution?

2. I did an test i use the FFT.vi,  the FFT Power spectrum.vi and the PSD.vi on an signal.

Result obtained,i was able to verify between the FFT and the FFT Power spectrum but i could not verify the PSD answer.

PSD= power spectrum in Vrms^2 / freq resolution * noise power bandwidth of window

how do i adjust the noise power bandwidth of window?

[CoastalMaineBird]

Alas, I am not qualified to answer those questions.
how do i adjust the noise power bandwidth of window?
I'm not sure what the "bandwidth" of a window is. The window function you use operates on a timewave. It has an amplitude factor associated with it (Hanning = 0.5, FlatTop = 0.281, etc.) . But AFAIK, it doesn't have a "bandwidth" number.

The term "normalized" would mean to me that the spectral peak (highest amplitude magnitude) is multiplied by some factor X to make it 1.0. All the other spectral bins would then be multiplied by this same X and would thuse come out as some number between 0 and 1.

These are reasonably educated guesses, but guesses nonetheless.

[celynn]

Say can you demostrate how would you calculate the coherence between two signals using the FFT power spectrum.vi and cross spectrum.vi?

[CoastalMaineBird]

See the link I posted above. It does just that.