AutoCorrelation/CrossCorrelation

[vedran]

Hi,

i have some Ni-DAQ-Card and LabView 7.0. i'm working with 2 signlas: X and Y. What i need is:

H(jw)= AutoCorrelation(X) / CrossCorrelation(X and Y)

What is the easyest way to do this?

Problem: AutoCorrelation-Icon have 1 output, and CrossCorrelation have 2 outputs (magnitude and phase) and i dont know how to divide that.

Thanx really
vedran

[Ian_Ren]

Hi, vedran

This is what I would do if I were you.

1) convert CrossCorrelation from magnitude and phase to a complex number, and then convert the complex number to real and imaginary parts.(Both functions are available in the Numberic->Complex Palettes)

2) Now let's assume the cross Correlation is C+iD, and AutoCorrelation is A, then

A/(C+iD)=A*(C-iD)/(C+iD)*(C-iD)=A*(C-iD)/(C^2+D^2).

Hope this helps.

Ian Ren

Roush Anatrol.

[Ian_Ren]

You can actually do complex divide directly in LabView.

Ian Ren

[vedran]

could u explain it please

[Ian_Ren]

Hi, vedran

Attached is a simple example on how to work on the complex number. I cannot find the auto/cross correlation functions in LabView, so I used auto power and cross power instead.

Regards

Ian

[Ian_Ren]

Hi, vedran

Both AutoCorrelation and CrossCorrelation should be real (in time domain), I think.

Are you actually trying to calculate the transfer function? then you may be using autopower and crosspower spectrum.

Ian