Rohde & Schwarz 1311.6010.22, User Manual

Page: 132 / 1451

Concepts and Features
R&S
®
ZNB/ZNBT
132 User Manual 1173.9163.02 ─ 53
common-mode rejection ratio (CMRR). It can be calculated as |S
dd21
|/|S
cc21
| (see
Chapter 5.3.6.2, "Mixed Mode Parameters" , on page 130). The general definition of the
complex CMRR between two ports (at least one of them balanced) is given below.
Imbalance and common-mode rejection ratio can only be measured if more than 2 test
ports are available on the VNA and connected
switch matrices .
General Definition
In general, imbalance and CMRR are quantities with two numeric indices, indicating
the logical output port and the logical input port of the DUT during the measurement
(Imb
<out><in>
, CMRR
<out><in>
).
●
DUT with single-ended logical port i and balanced logical port j:
DUT
Balanced
port
Log.
NWA
port
Single-
ended
port
Physical port c
Logical port j
(balanced)
Physical port d
Logical port i
(single-ended)
Physical port a
– 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
)
Measurement Results