Windowing - Agilent Technologies 8719D User Manual

Windowing

The analyzer provides a windowing feature that makes time domain measurements more useful
for isolating and identifying individual responses. Windowing is needed because of the abrupt
transitions in a frequency domain measurement at the start and stop frequencies. The band
limiting of a frequency domain response causes overshoot and ringing in the time domain
response, and causes a non-windowed impulse stimulus to have a sin(kt)/kt shape, where
k = a/frequency span and t = time (see F'igure 6-71). This has two effects that limit the
usefulness of the time domain measurement:
Finite impulse width (or rise time). F'inite impulse width limits the ability to resolve
n
between two closely spaced responses. The effects of the finite impulse width cannot be
improved without increasing the frequency span of the measurement (see lhble 6-10).
by hiding low-level responses within the sidelobes of higher level responses The effects of
sidelobes can be improved by windowing (see lhble 6-10).
Application and Operation Conwpts
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Figure 6-70. Masking Example
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