Concepts and Features
R&S
®
ZNC
55
User Manual 1173.9557.02 ─ 13
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 param-
eters 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.
3.3.5.3
Imbalance Parameters
An ideal unbalance-balance transformer (balun) converts an unbalanced signal into a
balanced one and vice versa. When it is driven with an unbalanced signal at its physical
port k, unbalanced signals with equal amplitude and opposite phase appear at the phys-
ical ports m and n.
This means that the ratio –S
km
/S
kn
of the physical transmission coefficients of an ideal
balun equals 1. This ratio is called imbalance; it is a measure for the deviation of the balun
from ideality. The definition of the imbalance of a DUT with one or two balanced ports
and physical port numbers k < l, m < n is given below.
●
Bal.
port
Physical
port m
Physical
port n
DUT
Logical port j
(balanced)
Log.
VNA
port
Single-
ended
port
Logical port i
(single-ended)
Physical port k
The imbalance of a DUT with a single ended logical input port i and a balanced logical
output port j is defined as Imb
ij
= –S
km
/S
kn
and Imb
ji
= –S
mk
/S
nk
.
●
Bal.
port
DUT
Log.
VNA
port
Bal.
port
Log.
VNA
port
Physical
port m
Logical port j
(balanced)
Physical
port n
Logical port i
(balanced)
Physical
port k
Physical
port l
The imbalance of a DUT with a balanced logical input port i and a balanced logical
output port j is defined as Imb
ij
= –(S
km
– S
kn
)/(S
lm
– S
ln
).
Measurement Results
