39
Figure 3.14 – FFT Function
Select FFT window
Windows reduce spectral leakage in the FFT spectrum. The FFT assumes
that the YT waveform repeats forever. With an integral number of cycles,
the YT waveform starts and ends at the me amplitude and there are no
discontinuities in the signal shape A non-integral number of cycles in the
YT waveform causes the signal start and end points to be at different
amplitudes. The transitions between the start and end points cause
discontinuities in the signal that introduce high-frequency transients.
Table 3.13 – FFT Window Description
Best frequency
resolution, worst
magnitude resolution.
This is essentially the
same as no window.
Symmetric transients
or bursts. Equal-
amplitude sine waves
with fixed frequencies.
Broadband random
noise with a relatively
slowly varying
spectrum.
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