Specifications

Chapter 15 149
Concepts
Time Gating Concepts
Concepts
NOTE Table 15-3 below applies only to ESA spectrum analyzers. PSA gated
LO time gating is not affected by analyzer sweep times (unless the
sweep time is set too fast, Meas Uncal appears on the screen and the
sweep time will need to be increased).
Table 15-3 Suggested Sweep Times for an ESA at 401 Sweep Points and a
Known Pulse Repetition Interval or Pulse Repetition
Frequency
Pulse Repetition
Interval (PRI)
Pulse Repetition
Frequency (PRF)
Sweep Time (minimum)*
50 µs 20 kHz 20.1 ms
100
µs 10 kHz 40.1 ms
500
µs 2 kHz 201 ms
1 ms 1 kHz 401 ms
5 ms 200 Hz 2.01 s
10 ms 100 Hz 4.01 s
16.7 ms 60 Hz 6.7 s
20 ms 50 Hz 8.02 s
33.3 ms 30 Hz 13.4 s
50 ms 20 Hz 20.1 s
100 ms 10 Hz 40.1 s
>170 ms Use the MAX HOLD trace function and take several measurement sweeps.
* The number of sweep points can be set to values between 101 and 8192. The minimum
sweep time is equal to the (number of sweep points minus 1) times (pulse repetition
interval).
Table 15-4 If You Have a Problem with the Time-Gated Measurement
Symptom Possible Causes Suggested Solution
(ESA only) Erratic analyzer
trace with random vertical
lines or dropouts extending
below the peak trace
amplitude.
1) Sweep rate too fast to
ensure at least one gate
occurrence per trace point.
2) Detector may be set to
something other than peak,
sample or average.
Increase sweep time until
dropouts disappear. See
Table 15-3 for sweep time
calculations.