Figure 2-62 Block Diagram Of The Spectrum Analyzer With Time Gate - Agilent Technologies 8560E User Manual

Making Measurements
Example 11: Time-Gated Measurement
Figure 2-62 Block Diagram of the Spectrum Analyzer with Time Gate
The gate within the analyzer is opened and closed based on four factors:
• An externally supplied transistor-transistor logic (TTL) signal.
• The gate control, or trigger mode (positive or negative edge
• The gate delay setting, which determines how long after the trigger
• The gate length setting, which determines how long the gate is on for
To understand time-gating better, consider a spectrum measurement
performed on two pulsed-RF signals. You need to consider the timing
interaction of three key signals that are present during this
measurement. The three signals are:
• The pulsed-RF signal under test.
• The gate trigger signal, supplied from the signal source.
• The gate output signal, available from a BNC connector on the rear
The timing interactions between the three key signals are best
understood if you observe them first on a oscilloscope. Figure 2-63
shows each of the signals as the would appear on the oscilloscope.
Keep in mind the main goal: to measure the spectrum of pulse train
number 1 and determine if it has any low-level modulation or spurious
signals.
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triggering, or positive or negative level triggering).
signal the gate actually becomes active for the edge trigger mode.
the edge trigger mode.
panel of the spectrum analyzer. This transistor-transistor logic
(TTL) signal is low when the gate is "off" (masking) and high when
the gate is "on" (measuring).
Chapter 2