[Kst] calculating the Amplitude Spectrum

[Barth Netterfield]

You had "Interleaved Average" checked in the Power Spectrum Dialog.  This is 
useful if your input spectrum is random phase non-white gaussian noise and you 
want to determine the underlying power spectrum, but not correct in your case, 
where you want to determine the amplitude of a coherent line. 

Un-checking this option gives a line of amplitude 0.999911705184 at  
34.5011749626 Hz  (with the remainder of the power spread into nearby bins).

Sqrt(2) vs 1 is related to the definition of "one sided" or "two sided" power 
spectrum or some such thing like that.

cbn

On January 31, 2014 02:07:11 PM Chris Stoughton wrote:

> I'm having trouble understanding the normalization of power spectra.
> 
> I generate a sine signal with amplitude 1 Volt, and use kst2 to plot the
> amplitude spectrum.
> I expect to get a peak of sqrt(2)*1 Volts in the frequency bin that
> includes the sine wave.
> 
> Instead, it seems to have a value of 0.037, instead of 1.4.
> 
> I have attached the input data file PowerSpectrum.txt, the kst file
> PowerSpectrum.kst, and a PDF of the plot as it appears when I run kst2
> PowerSpectrum.kst/
> 
> Here is the version I am running.
> 
> Kst 2.0.x Revision 662928007df2521469b471a899017ed89a735d9b
> 
> 
> Thanks for your help.

-- 
C. Barth Netterfield
416-845-0946