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About S-parameters
S-parameters (scattering parameters) are used to describe the way a device
modifies a signal. The FieldFox can measure four S-parameters. The syntax for
each parameter is described by the following:
The FieldFox automatically switches the internal source and receivers to make
both forward and reverse measurements. Therefore, the FieldFox can measure
all four S-parameters with a single connection.
When the source comes from port 1, the measurement is said to be in the
forward direction.
When the source comes from port 2, the measurement is said to be in the reverse
direction, which requires Option 122.
S11 and S22 reflection measurements are used to measure the amount of
reflections off the corresponding DUT port. Low reflections means there is a
good impedance match between the source and DUT.
S21 and S12 transmission measurements are used to measure the loss or gain
through a DUT over a specified frequency range. Both ends of the DUT must be
connected to the FieldFox. The FieldFox signal source is transmitted out one of
the test port connectors, through the DUT, and into the other test port connector.
How to measure S-parameters
1. Press Preset then
2. Press Measure 1 then choose from the following:
OR select a multi-trace configuration. Learn more on page 21.
3. Press Freq/Dist then either
4. Press BW 2 then
20
S (out | in)
out = FieldFox receiver port
in = FieldFox source port
Preset
Reflection measurement at port 1.
S11
o
Forward 2-port transmission measurement.
S21
o
Reverse 2-port transmission measurement. Requires Opt 122.
S12
o
Reflection measurement at port 2. Requires Opt 122.
S22
o
Frequency Range for the measurement.
IFBW
Narrower bandwidths require more time to sweep, but lowers trace noise.
and
or
Start
Stop
Center
to select the IF Bandwidth for the measurement.
and
to enter a
Span
N9923A FieldFox User's Guide
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