User Manual

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21.3 Reference
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This is a spectral artifact that occurs as a result of aliasing of
the high frequency component of a signal with the A/D
converter sampling rate. Although visible during measurement,
it
does not exist in reality.
Because no anti-aliasing filter is present, fine square waves are
monitored through the high-frequency amplifier, so the corners
of square waves include high-frequency components.
Anti-aliasing filter
・In FFT processing, when the frequency bandwidth of the input signal is
unlimited, frequency spectrum components that do not exist will appear, due
to aliasing. To prevent this, a low-pass filter is required which cuts off the
input waveform at 1/2 of the sampling frequency. Such a low-pass filter is
called an anti-aliasing filter.
・The 8938 FFT ANALOG UNIT incorporates an anti- aliasing filter and
therefore allows the 8826 to perform FFT analysis without being subject to
aliasing.
(1) When an anti-aliasing filter is not used.