VNA concepts and features
R&S
®
ZNL/ZNLE
226
User Manual 1178.5966.02 ─ 19
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.
9.3.6.1
Balanced port configurations
Defining a balanced logical port requires two physical ports.
You can combine the two physical VNA ports to a single balanced (logical) port and
then assign arbitrary, independent reference impedance values to its differential and
common mode.
Example:
Bal.
port
Differential mode
Z
ref
= Z
0d
Common mode
Z
ref
= Z
0c
DUT
Balanced port:
Log.
VNA
port
The "Balanced Ports" dialog allows you to switch to balanced operation and to define
the reference impedances the differential and common mode.
Depending on the test setup, the analyzer provides different types of mixed mode
parameters; refer to the following sections for details.
Measurement results
