Gated Video Measurement - Keysight X Series Measurement Manual

Making Time-Gated Measurements

Gated Video Measurement

Gated Video Measurement
This procedure utilizes gated video to gate the FM signal. For concept and theory
information about gated video see
Step
1 Set the analyzer to
the Spectrum
Analyzer mode.
2 Preset the analyzer
3 Set the center
frequency, span,
reference level and
attenuation.
4 Set analyzer points to
401 and sweep time
to 2000 ms.
Good practices for determining the minimum sweep time for gated video:
NOTE
In the event that the signal is not noisy, the sweep time can be set to less than
(
# sweep points 1
previous sweep time calculation, we can use the "gate off time" where sweep time equals
(
# sweep points 1
our example we could use a sweep time of 400 points times 1 ms or 400 ms –
( ) × (
401 1 – 5ms 4ms
capturing the pulse using "gate off time". If trace points are still showing values of zero power,
increase the sweep time by small increments until there are no more dropouts.
5 Set the Gate source to
the external trigger
input on the rear
panel:
Action
• Press Mode, Spectrum
Analyzer.
• Press Mode Preset.
a. Press FREQ Channel,
Center Freq, 40, MHz.
b. Press SPAN X Scale,
Span, 500, kHz.
c. Press AMPTD Y
Scale, Ref Level, 10,
dBm.
a. Press Sweep/Control,
Points, 401, Enter.
c. Press Sweep Time,
2000, ms.
) ×
– PRI (pulse repetition interval
. (Gate off time is defined as
) gate off time ×
–
. Increase the video band width to improve the probability of
)
– = 400ms
• Press Sweep/Control,
Gate, More, Gate
Source, External 1.
"How time gating works" on page
Notes
This enables the spectrum analyzer
measurements.
For gated video, the calculated sweep time should
be set to at least
( ) ×
# sweep points 1 –
ensure that the gate is on at least once during each
of the 401 sweep points. In this example, the PRI is
5 ms, so you should set the sweep time to 401
minus 1 times 5 ms, or 2 s. If the sweep time is set
too fast, some trace points may show values of
zero power or other incorrect low readings. If the
trace seems incomplete or erratic, try a longer
sweep time.
(as calculated above). Instead of using PRI in the
)
PRI GL –
104
199.
PRI (pulse repetition interval
, where GL = Gate Length.) In
to
)