Specifications

Chapter 8 63
Making Time-Gated Measurements
Gated LO Measurement (PSA)
Making Time-Gated Measurements
In Figure 8-3 the vertical green parallel bars represent the gate
settings. The first (left) bar is set at the delay time while the second
(right) bar is set at the gate length, measured from the first bar. The
trace of the signal in this time-domain view is the RF envelope. The
gate signal is triggered off of the positive edge of the trigger signal.
When positioning the gate, a good starting point is to have it extend
from 20% to 80% of the way through the pulse (for the PSA with
linear-phase RBW filters).
While gate view mode is on, move the gate delay, length and polarity
around. Notice the changes in the vertical gate bars while making your
changes. Set the gate delay, length and polarity back to the step 3
settings.
NOTE The PSA time gate triggering mode uses positive and negative edge
triggering. Level triggering is not available.
Step 5. Turn the gate view off and enable the gate settings (see the right-side
display in Figure 8-4):
Press
Sweep, Gate Setup, Gate View (Off).
Press
Sweep, Gate (On).
Figure 8-4 Pulsed-RF FM Signal (Left), Gated FM Signal (Right)
Step 6. Turn off the pulse modulation on ESG #1 by pressing
Pulse, Pulse so
that Off is selected.
Notice that the gated spectrum is much cleaner than the ungated
spectrum (as seen in Figure 8-4). The spectrum you see with the gate on
is the same as a frequency modulated signal without being pulsed. The
displayed spectrum does not change and in both cases, you can see the
two low-level modulation sidebands caused by the narrow-band FM.