Chapter 2
29
Measurement Concepts
Stimulus Response Measurements
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Stimulus Response Measurements
Stimulus/response measurements require a source to stimulate a device
under test (DUT), a receiver to analyze the frequency response
characteristics of the DUT, and, for return loss measurements, a
directional coupler or bridge. Characterization of a DUT can be made in
terms of its transmission or reflection parameters. Examples of
transmission measurements include flatness and rejection. Return loss
is an example of a reflection measurement.
A spectrum analyzer combined with a swept source forms a
stimulus/response measurement system that operates the same as a
single channel scalar network analyzer. The swept source output
frequency must be made to precisely track the analyzer input frequency
for good narrow band operation. A narrow band system has a wide
dynamic measurement range.
There are four basic steps in performing a stimulus/response
measurement, whether it is a transmission or a reflection
measurement.
1. Connect the spectrum analyzer and tracking source together,
including making the trigger, sweep, reference and LAN connections
and entering the external source information. Instructions for doing
this can be found in
“Setting Up Your Signal Analyzer and Signal
2. Select the spectrum analyzer and source measurement settings, and
connect the cables and accessories needed to make the desired
measurement (but do not include the DUT). Note that the source
setup is done using the functions under the spectrum analyzer
Source
key.
3. Do the calibration measurement (error correction).
4. Attach the DUT and perform the measurement.