DFT, Sine, Real and Imaginary Spectrum.

Cuthbert Nyack
Most of the applets show only the magnitude of the spectra. here the real part, imaginary part, magnitude and phase of the DTFT and the DFT are shown.

eg parameters:-
(3.0, NA, 0.01, 6.04, 25, NA, 6, 375.0, 15.0, 0.12) a sine.
The DFT has only one line of magnitude 12.5 in the spectrum at 3rad/s, which is also the magnitude of the imaginary component. All real components of the DFT are zero.

(3.0, NA, 0.51, 6.54, 25, NA, 6, 375.0, 15.0, 0.12) a cosine.
Here the spectrum also has only one component but this time, it is real. All the imaginary components of the DFT are zero.

(3.0, NA, 0.8, 6.83, 25, NA, 6, 375.0, 15.0, 0.12)
Here the spectrum has both real and imaginary parts.
(3.0, NA, 0.01, 7.27, 50, NA, 15, 375.0, 15.0, 0.12)
Shows the effect on the DFT spectrum of sampling 3.5 periods of the sinulsoid, spectrum mostly real.
(3.0, NA, 0.51, 7.69, 50, NA, 15, 375.0, 15.0, 0.12)
Shows the effect on the DFT spectrum of sampling 3.5 periods of the sinulsoid, spectrum mostly imaginary.
Most of the applets show the magnitude of the spectrum which is sometimes referred to as the power spectrum.



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COPYRIGHT 2007 Cuthbert Nyack.