spectral analysis using excel 1

[1900paws1]

This is a pretty low level question. I have excel and need to do a spectral analysis of time based data. I did a FT in Excel, but don't have a clue regarding the output....it's a list of imaginary numbers. All I need is a simple spectral analysis of the data. I can select the amount of data to equal a power of 2. How do I get the analysis done and a graphical ouput?

I will greatly appreciate any insight you can provide.

1900paws1

 

[electricpete]

Take the magnitude of the complex results using imabs (part of the complex analysis toolbox).

You will also get twice as much data as you really need based on symmetry of the fourier transform (assuming the input to your FFT were real numbers). The data will be symmetric about zero frequency. Throw out the negative frequencies (plot only frequencies from 0 to max).

Also if your original data is truncated in time by the rectangular sampling window and not periodic with a period = sample window length, you may consider premultiplying by a window funciton (such as Hanning) to minimize spectral leakage.

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[1900paws1]

electricpete: thanks so much for the quick reply! I think I understand, but please be patient with me, I'm new at this FFT thing.

1900paws1

 

[1900paws1]

electricpete: I found out ii's in the "functions" tab. Dah, sorry for the simple questions.

Don