Concepts and features
R&S
®
ZNA
135
User Manual 1178.6462.02 ─ 20
VNA
1
2
Physical VNA ports
Common
mode
Differential
mode
Physical
transformer
(balun)
DUT
VNA
1
2
DUT
Balanced port
Internal balance-
unbalance
conversion
Logical
VNA ports
Unbalance-balance conversion avoids the disadvantages of real transformers:
●
There is no need to fabricate test fixtures with integrated baluns for each type of
DUT.
●
The measurement is not impaired by the non-ideal characteristics of the balun (e.g.
error tolerances, limited frequency range).
●
Calibration can be performed at the DUT's ports. If necessary (e.g. to compensate
for the effect of a test fixture), it is possible to shift the calibration plane using length
offset parameters.
●
Differential and common mode parameters can be evaluated with a single test
setup.
4.3.6.1
Balanced port configurations
Defining a balanced logical port requires two physical ports.
The physical VNA ports are equivalent and can be freely combined to balanced (logi-
cal) ports. Moreover, it is possible to assign arbitrary, independent reference impe-
dance values to each unbalanced port and to the differential and common mode of
each logical port.
Measurement results
