Agilent Technologies E5071C Manual page 489

E5071C
Differential matching circuit embedding converts measured S-parameters
to those when a matching circuit is added to the DUT's differential mode
port.(L2 in there figure Measurement circuit simulated by fixture simulator)
Differential port reference impedance conversion converts a differential
port reference impedance to an arbitrary impedance. Port reference
impedance Z [ohm] at the two single-ended ports before balance
conversion is automatically converted to 2Z [ohm] for differential mode
port and Z/2 [ohm] for common mode port after balance conversion.
Accordingly, if port reference impedance conversion is not performed for
the two single-ended ports before balance conversion, differential mode
port reference impedance Zd becomes 50 ohm * 2 = 100 ohm , and
common mode port reference impedance Zc becomes 50 ohm / 2 = 25
ohm . Since the differential port is terminated with 200 ohm in the
figure,Measurement circuit of balance SAW filter, differential port reference
impedance Zd should be set to 200 ohm.
Advantages of Balanced DUT Evaluation using Fixture Simulator
Balanced device evaluation using the fixture simulator offers the following
advantages:
Calibration reference plane can be easily moved to the DUT's
•
terminal after calibration is performed at the connectors where
calibration standards can be connected. Undesired network can be
removed to eliminate measurement errors (port extension, network
de-embedding).
Characteristics of a DUT, including desired matching circuits, can be
•
obtained easily (matching circuit embedding, differential matching
circuit embedding). Port reference impedance can be set freely (port
reference impedance conversion, differential port reference
impedance conversion).
Differential mode and common mode signal evaluation (mixed-mode
•
S-parameter evaluation) can be performed easily (balance-unbalance
conversion).
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