Keysight x-series Measurement Guide

104
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 “How time gating works” on page 199.
Step Action Notes
1 Set the analyzer to
the Spectrum
Analyzer mode.
• Press Mode, Spectrum
Analyzer.
This enables the spectrum analyzer
measurements.
2 Preset the analyzer • Press Mode Preset.
3 Set the center
frequency, span,
reference level and
attenuation.
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.
4 Set analyzer points to
401 and sweep time
to 2000 ms.
a. Press Sweep/Control,
Points, 401, Enter.
c. Press Sweep Time,
2000, ms.
For gated video, the calculated sweep time should
be set to at least
to
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.
NOTE Good practices for determining the minimum sweep time for gated video:
In the event that the signal is not noisy, the sweep time can be set to less than
(as calculated above). Instead of using PRI in the
previous sweep time calculation, we can use the “gate off time” where sweep time equals
. (Gate off time is defined as , where GL = Gate Length.) In
our example we could use a sweep time of 400 points times 1 ms or 400 ms –
. Increase the video bandwidth to improve the probability of
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:
• Press Sweep/Control,
Gate, More, Gate
Source, External 1.
# sweep points 1–()PRI (pulse repetition interval×)
# sweep points 1–()PRI (pulse repetition interval×)
# sweep points 1–()gate off time×
PRI GL–
401 1–()5ms 4ms–()× 400ms=

Keysight x-series Specifications

General

Analysis Bandwidth	Up to 1 GHz (depending on model)
Real-Time Bandwidth	Up to 1 GHz (depending on model)
Form Factor	Benchtop
Connectivity	LAN, USB, GPIB
Resolution Bandwidth	1 Hz to 10 MHz (depending on model)