Agilent Technologies 2000 X, User Manual

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Math Waveforms
4
Agilent InfiniiVision 2000 X-Series Oscilloscopes User's Guide 75
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 Agilent Application Note 243,
The Fundamentals of Signal Analysis at
"http://cp.literature.agilent.com/litweb/pdf/5952- 8898E.pdf."
Figure 7 Aliasing