FFT, 2 Sines with Hamming window.
The use of a window in conjunction with the FFT reduces the variation
in the spectrum that occurs when an integer or nonteger number
of periods is sampled. A broadening of the spectrum is the price paid
for this reduction in variation.
eg parameters (4.0, 4.2, 0.0, 70.00, 512, 10, 185, 10.0, 150.0, 0.04)
This is the case of 1 sinusoid, varying T2 shows little variation in
the spectrum of the signal. On the other hand it is no longer possible
to get a spectrum consisting of a single line.
eg parameters (4.0, 4.2, 1.0, 129.25, 512, 10, 185, 10.0, 150.0, 0.04)
show that in order to distinguish 2 sinusoids of equal amplitude
separated by 0.2rad/s, then the sampling interval > 100s. For
a separation of 0.1rad/s an even longer interval is required.
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COPYRIGHT © 2007 Cuthbert Nyack.