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9-5 GATING Gating is a time filter that allows for removing unwanted time-domain
responses by gating the desired response. We can view the isolated re
-
sponse in both time domain—and in the frequency domain—using the
FREQUENCY WITH TIME GATE selection (Figure 9-17).
There are four different gate shapes available: MINIMUM, NOMI
-
NAL, WIDE, and MAXIMUM (Figure 9-18). The 37xxxE defaults to
the NOMINAL gate. To specify a different shape simply enter the Gate
menu and select the desired gating shape. The MINIMUM has the
sharpest rolloff and some frequency domain ripple, while MAXIMUM
has the least rolloff and best residual ripple. Figures 9-18A through
9-18D, on the next page, show gating shapes.
The combinations of gate/window shapes will be restricted. For the
MINIMUM gate shape, the LOW and MIN SIDELOBE window shape
will not be allowed. For the NOMINAL gate shape, the MIN SIDE
-
LOBE window will not be allowed. If the user has set the window
shape to MIN or LOW SIDELOBE and changes the-gate shape to
MINIMUM, the window will be reset to NOMINAL. If the user has set
the window to MIN SIDELOBE and changes the gate shape to NOMI-
NAL, the window will be reset to LOW SIDELOBE. Gate shapes will
be adjusted in a similar manner.
GATING TIME DOMAIN
9-12 37xxxE OM
G A T E
D I S T A N C E
G A T E A P P L I E D
G A T I N G
Figure 9-17. Gating
Figure 9-18. Gating Menus
LOWPASS TIME
DOMAIN SETUP
SET WINDOW
NOMINAL
SET GATE
SET DC TERM
XXX.XXX
PREVIOUS MENU
PRESS <ENTER>
TO SELECT
LOWPASS TIME
DOMAIN SETUP
START
XXX.XXX ps
STOP
XXX.XXX ps
CENTER
XXX.XXX ps
SPAN
XXX.XXX ps
MARKER RANGE
RESPONSE
IMPULSE/STEP
MORE
PRESS <ENTER>
TO SELECT
SELECT GATE
SHAPE
MINIMUM
NOMINAL
WIDE
MAXIMUM
HELP
PRESS <ENTER>
TO SELECT