Concepts and Features
R&S
®
ZNB/ZNBT
125
User Manual 1173.9163.02 ─ 38
–
Imb
ji
= –S
ca
/S
da
and Imb
ij
= –S
ac
/S
ad
–
CMRR
ji
= S
dsji
/S
csji
and CMRR
ij
= S
sdij
/S
scij
●
DUT with balanced logical ports i and j:
DUT
Balanced
port
Log.
NWA
port
Balanced
port
Log.
NWA
port
Physical port c
Logical port j
(balanced)
Physical port d
Logical port i
(balanced)
Physical port a
Physical port b
–
Imb
ji
= –(S
ca
– S
cb
)/(S
da
– S
db
), for i
≠
j
–
CMRR
ji
=S
ddji
/S
ccji
Differential Imbalance
A (differential) imbalance can also be calculated if the second balanced DUT port is
connected to two single-ended logical ports:
DUT
Balanced
port
Balanced
port
Log.
NWA
port
Physical port c
Logical ports j,k
(single-ended)
Physical port d
Logical port i
(balanced)
Physical port a
Physical port b
Imb
jk-i
= –(S
ca
– S
da
)/(S
cb
– S
db
)
Imb
i-jk
= –(S
ac
– S
ad
)/(S
bc
– S
bd
)
4.3.6 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.
The default values for the balanced port reference impedances are derived from the
default reference impedance of the physical analyzer ports (Z
0
= 50 Ω):
●
The default value for the differential mode is Z
0d
= 100 Ω = 2*Z
0
.
●
The default value for the common mode is Z
0c
= 25 Ω = Z
0
/2
Measurement Results
