NF FRA51602, Instruction Manual

Page: 174 / 286

5.5 Graph display
5
-
18
FRA 51602
■ The aperture setting
【
Graph
】
–
[PHASE RANGE]
–
[APERTURE]
is the value for the width of the moving average
window of the phase characteristic for the group delay display.
Larger values for the setting reduce noise and produce a smooth group delay characteristic, but abrupt
changes are not represented. The aperture is set to an even number that is less than the number of
frequency points in the sweep (but no more than 200). Set a value that is appropriate for the equipment
under test.
The effect of the aperture setting on the group delay characteristic of the bandpass filter for
communication is shown in the figure below, where the upper parts of the figures show the gain
characteristics and the lower parts show the group delay characteristics. We can see that higher aperture
settings result in a smoother group delay characteristic and that the gain characteristic is not affected.
Aperture setting = 2 Aperture setting = 20
1) Select APERTURE.
2) Tap
3) Enter the moving average
window width.