Specifications

62 Chapter 8
Making Time-Gated Measurements
Gated LO Measurement (PSA)
Making Time-Gated Measurements
Gated LO Measurement (PSA)
This procedure utilizes gated LO to gate the FM signal. For concept and
theory information about gated LO see “How Time Gating Works” on
page 135.
Step 1. Set the PSA center frequency, span and reference level:
Press
FREQUENCY Channel, Center Freq, 40, MHz.
Press
SPAN X Scale, Span, 500, kHz.
Press
AMPLITUDE Y Scale, Ref Level, −15, dBm.
In Figure 8-4 (left), the moving signals are a result of the pulsed signal.
Using delta markers with a time readout, notice that the period of the
spikes is at 5 ms (the same period as the pulse signal). Using time
gating, these signals are be blocked out, leaving the original FM signal.
Step 2. Set the gate source to the rear external trigger input:
Press
Sweep, Gate Setup, Gate Source, Ext Rear.
Step 3. Set the gate delay to 2 ms and the gate length to 1 ms. Check that the
gate trigger is set to positive:
Press
Sweep, Gate Setup, Delay, 2, ms.
Press
Sweep, Gate Setup, Length, 1, ms.
Press Sweep, Gate Setup, Polarity (Pos).
Step 4. Use the PSA gate view display to confirm the gate “on” time is during
the RF burst interval (alternatively you could also use the oscilloscope
to view the gate settings):
Press
Sweep, Gate Setup, Gate View (On).
Figure 8-3 Viewing the PSA Gate Settings with Gated LO
In Figure 8-3 the gray vertical line (the far left line outside of the RF
envelope) represents the location equivalent to a zero gate delay.