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ES User’s Guide 5-15
Optimizing Measurements
Reducing Mismatch Errors
Reducing Mismatch Errors
Mismatch errors are due to the fact that the analyzer’s port impedances
are not exactly 50 ohms or 75 ohms across the frequency range. Source
match errors are produced on the source side of the DUT; load match
errors on the load side. If the DUT is not connected directly to the port,
the mismatch errors due to cables, adapters, etc. are considered part of
the source or load match errors. Source match and load match error
terms can be reduced by using the methods described in this section.
Reducing Mismatch Errors in a Reflection
Measurement
The best way to reduce mismatch errors in a reflection measurement of a
two-port device is to perform a two-port calibration directly at the point
that will connect to the DUT, using the exact frequency parameters that
you will be using for the measurement. Though not quite as accurate as a
two-port calibration, a one-port calibration can also be used to reduce
mismatch errors. A one-port calibration offers the advantage of faster
measurement speeds than when using a two-port calibration. The
accuracy of a one-port calibration for a two-port device can be increased
dramatically by terminating the output port of the device with a high
quality Z
0
termination (a load from a calibration kit, for example)
instead of connecting it to the analyzer.
1. Set up your S
11
port 1 reflection measurement or S
22
port 2 reflection
measurement, and frequency parameters.
2. Press or .
3. Follow the instructions on the display.
See Chapter 6 for more information on calibration choices for reflection
measurements.
CAL
User 2-Port User 1-Port