E5071C
484
On the other hand, DUT port 2 is a balanced port that cannot be connected
directly to the test port of the network analyzer. Usually, a balun
(BALance-UNbalance transformer) is used to convert the DUT's balanced
port to an unbalanced port and to connect the converted port to the test
port of the network analyzer. Matching circuits are mounted in the test
fixture as shown in the following figure.
DUT evaluation using an actual test fixture
Problems in Measurement with Actual Test Fixture
Evaluating a balanced device with an actual test fixture involves the
following problems:
• Calibration cannot be performed at the DUT's terminals. (A DUT's
terminals are in the test fixture and calibration standards cannot be
connected to them. In addition, it is very difficult to obtain calibration
standards that can be used to calibrate a balanced port.) As a result,
calibration is performed at appropriate connectors connected to the
test fixture, and the network between the calibration reference plane
and the DUT's terminals induces measurement errors.
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