VNA Concepts and Features
R&S
®
ZNL/ZNLE
227
User Manual 1178.5966.02 ─ 07
●
S
<mout><min>21
is the mixed mode forward transmission coefficient, defined as the
ratio of the wave quantities b
2
(mode mout) to a
1
(mode min) (forward measure-
ment with matched output and a
2
= 0).
●
S
<mout><min>12
is the mixed mode reverse transmission coefficient, defined as the
ratio of the wave quantities b
1
(mode mout) (reverse measurement with matched
input, b
1
' in the figure above and a
1
= 0) to a
2
(mode min).
●
S
<mout><min>22
is the mixed mode output reflection coefficient, defined as the ratio of
the wave quantities b
2
(mode mout) (reverse measurement with matched input, b
2
'
in the figure above and a
1
= 0) to a
2
(mode min), measured at PORT 2.
If <mout> is different from <min>, the S-parameters are called mode conversion fac-
tors.
Mixed Mode Parameters for Different Test Setups
Which types of mixed mode parameter are available depends on the measured device
and the port configuration of the analyzer. The following examples of mixed mode
parameters can all be obtained with a 2-port analyzer.
1. DUT with only single-ended ports: No balanced port definition necessary, the ana-
lyzer provides single-ended multiport parameters.
2. DUT with one balanced port: Only reflection and mode conversion measurements
with differential and common mode parameters.
8.3.6
Reference Impedances
Changing the reference impedances of the analyzer ports is often referred to as
renormalization of port impedances. Renormalization means that the measurement
results measured at 50 Ω (75 Ω) are converted into results at arbitrary port impedance.
●
Renormalization of the physical port impedances affects, e.g., S-parameters and
wave quantities in "Power" representation.
●
Renormalization of the balanced port impedances affects all measured quantities
that the analyzer provides for balanced ports.
The default reference impedance of a physical port is equal to the reference impe-
dance of the connector type assigned to the port (50 Ω or 75 Ω). It can be defined as a
complex value. For balanced ports, it is possible to define separate complex reference
impedances for differential and for common mode.
Measurement Results
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