FFT Spectral Analysis
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Keysight InfiniiVision 1200 X-Series and EDUX1052A/G Oscilloscopes User's Guide
63
Because the frequency span goes from
≈
0 to the Nyquist frequency, the best way
to prevent aliasing is to make sure that the frequency span is greater than the
frequencies of significant energy present in the input signal.
FFT Spectral Leakage
The FFT operation assumes that the time record repeats. Unless there is an
integral number of cycles of the sampled waveform in the record, a discontinuity is
created at the end of the record. This is referred to as leakage. In order to minimize
spectral leakage, windows that approach zero smoothly at the beginning and end
of the signal are employed as filters to the FFT. The FFT menu provides four
windows: Hanning, Flat Top, Rectangular, and Blackman-Harris. For more
information on leakage, see Keysight Application Note 243,
The Fundamentals of
Signal Analysis
at
http://literature.cdn.keysight.com/litweb/pdf/5952-8898E.pdf.
Figure 9
Aliasing
