Specifications

Chapter 15 141

Concepts

Time Gating Concepts

Concepts

Measuring a Complex/Unknown Signal

NOTE The steps below help to determine the spectrum analyzer settings when

using time gating. The steps apply to the time gating approaches using

gated LO on the PSA and gated video on the ESA.

This example shows you how to use time gating to measure a very

specific signal. Most signals requiring time gating are fairly complex

and in some cases extra steps may be required to perform a

measurement.

Step 1. Determine how your signal under test appears in the time domain and

how it is synchronized to the trigger signal.

You need to do this to position the time gate by setting the delay

relative to the trigger signal. To set the delay, you need to know the

timing relationship between the trigger and the signal under test.

Unless you already have a good idea of how the two signals look in the

time domain, you can examine the signals with an oscilloscope to

determine the following parameters:

• Trigger type (edge or level triggering)

• Pulse repetition interval (PRI), which is the length of time between

trigger events (the trigger period).

• Pulse width, or

• Signal delay (SD), which is the length of time occurring between the

trigger event and when the signal is present and stable. If your

trigger occurs at the same time as the signal, signal delay will be

zero.