Agilent Technologies E5071C Manual page 488

Measurement
First, the effect of an undesired network can be eliminated by port
extension and/or network de-embedding. In the above figure (DUT
connection when fixture simulator is used), since calibration standards
cannot be connected to the DUT terminals to perform calibration,
calibration should be performed at the connectors to the test fixture. Using
port extension and/or network de-embedding enables you to remove an
undesired network by using data processing and moving the calibration
reference plane to the DUT's side equivalently. This function is performed
for a single-ended port even if balance-unbalance conversion is applied to
the port.
Port reference impedance conversion converts measured S-parameters to
those at arbitrary port reference impedance. In the above figure
(Measurement circuit simulated by fixture simulator), since the single-
ended port of the DUT is connected to the E5071C's test port (50 ohm ,
single-ended), port reference impedance conversion is not required. This
function is performed for a single-ended port even if balance-unbalance
conversion is applied to the port.
Matching circuit embedding converts measured S-parameters to those
when a matching circuit is added to the DUT's terminal. This function is
performed for a single-ended port even if balance-unbalance conversion is
applied to the port.
Balance-unbalance conversion converts S-parameters measured at an
unbalanced state to mixed-mode S-parameters measured at a balanced
state. The balanced port signal can be evaluated by using differential mode
and common mode signals.
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