Agilent Technologies 8719D, User Manual

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Circuit
Circuit
Figure 6-70. Masking Example
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 shape, where
k = a/frequency span and t = time (see 6-71). This has two effects that limit the
usefulness of the time domain measurement:
n
Finite impulse width (or rise time).
impulse width limits the ability to resolve
between two closely spaced responses. The effects of the finite impulse width cannot be
improved without increasing the frequency span of the measurement (see 6-10).
6-71. Impulse Width, Sidelobes, and Widowing
Sidelobes.
The impulse sidelobes limit the dynamic range of the time domain measurement
by hiding low-level responses within the sidelobes of higher level responses The effects of
sidelobes can be improved by windowing (see 6-10).
Application and Operation Conwpts