Chapter 2 151
Making Measurements
Example 11: Time-Gated Measurement
Figure 2-79 Gate Positioning Parameters
Most control settings are determined by two key parameters of the
signal under test: the pulse repetition interval (PRI) and the pulse
width (τ). If you know these parameters, you can begin by picking some
standard settings. Table and Table summarize the parameters for a
signal whose trigger event occurs at the same time as the beginning of
the pulse (for example, SD is 0). If your signal has a non-zero delay, just
add it to the recommended gate delay.
Table 2-7 Suggested Initial Settings for Known Pulse Width (τ) and Zero
Signal Delay
Pulse width (τ) Gate Delay
(SD + τ/2)
Resolution
Bandwidth
(2>SUT)
Gate Length
(τ/4)
Video Bandwidth
(1/gate length)
4 µs3µs 1 MHz 1 µs 1 MHz
10 µs5µs 1 MHz 3 µs 1 MHz
50 µs25µs 100 kHz 13 µs 100 kHz
63.5 µs32µs 100 kHz 16 µs 100 kHz
100 µs50µs 100 kHz 25 µs 100 kHz
500 µs 250 µs 10 kHz 125 µs 10 kHz
1 ms 500 µs 10 kHz 250 µs 10 kHz
5 ms 2.5 ms 1 kHz 1.25 ms 1 kHz
10 ms 5 ms 1 kHz 2.5 ms 1 kHz
16.6 ms 8.3 ms 1 kHz 4 ms 1 kHz
33 ms 16.5 ms 1 kHz 8 ms 1 kHz
50 ms 25 ms 1 kHz 13 ms 1 kHz
100 ms 50 ms 1 kHz 25 ms 1 kHz
≥130 ms 65 ms 1 kHz 33 ms 1 kHz
When using the short gate delays, you may notice the gate delay time jitter by ±1 µs. This jitter is due to the
spectrum analyzer 1 MHz gate clock, and it does not indicate a problem.
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