HP 8590 E-Series - Using Time-Gating to View Signal

7. Set the video bandwidth to a value that is greater than 1 divided by the gate length. For
this example, the video bandwidth must be greater than l/13 ~LS, or 80 kHz. Press Isw),
VID BW AUTO MAN, 100 (kHz.
The spectrum analyzer displays only signal 1, not Both signal 1 and signal 2 (see
Figure 4-25).
t
REF .0 dBm
I ,............
Ami
ATTEN 10 dB
GTPOS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LOG : I
lilamu
,*,
z/
'1 ::,
GATE
LENGTH
GATE DELAY
25 psec
EDGE POL
pDs NEG
~~o~~~~~::::i_____, 9i;
CENTER 50.i00 "Ii;
SPAN 5.,000 ii;
RRES BW 100 kHz #UBW 100 kHz #SWP 12~ MS~C RT
Figure 4-25. Using Time-Gating to View Signal 1
8. To compare signal 1 to signal 2, we first place signal 1 (trace A) in the view mode. Press
(TRACE], VIEW A, TRACE A B C (so that B is underlined), CLEAR WRITE B .
9. To view the second signal, change the gate delay so that the gate output is under the
second signal. Since the second signal had a signal delay of approximately 85 ,q we set
the gate delay to 85 ,M plus the pulse width/2, or 110 p.s. Press CSWEEP], Gate Control ,
GATE DELAY 110 @ to set the gate delay to 110 ps. Using an oscilloscope can be helpful
in placing the gate output during the pulsed signal (see Figure 4-26).
4-30 Making Measurements