Math FFT
SelectinganF
FT Window
Windows reduce spectral leakage in the FFT spectrum. The FFT assumes that
the YT wave form repeats forever. With an integral number of cycles (1, 2 , 3,
...), the YT w
aveform starts and ends at the same amplitude and there are no
discontinuities in the signal shape.
A non-integ
ral 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.
Applying a window to the YT waveform c hanges the waveform so that the start
and stop values are close to each oth er, reducing t he discontinuities.
TPS2000B Series Digital Oscilloscope User Manual 65
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