The balance-unbalance conversion function calculates and displays the following parameters:
•Mixed mode S-parameters.
•Imbalance parameters.
•Common Mode Rejection Ratio.
Notation of mixed mode S-parameters:
•SxyAB, where:
B — Stimulus logical port number.
A — Response logical port number.
y — Stimulus logical port measurement mode.
x — Response logical port measurement mode.
•x and y represent logical ports measurement modes (See Balance-unbalance conversion):
s — Single-ended measurement mode (unbalanced).
d — Differential measurement mode (balanced).
c — Common measurement mode (balanced).
Thus,
Below are the four definitions of the mixed mode S-parameters for four topologies of balanced devices (See Balance-unbalance conversion).
The mixed mode S-parameters for single-ended-balanced devices (SE-Bal)
Logical port mode |
Stimulus |
Single-ended |
Differential |
Common |
Receiver |
Logical port number |
1 |
2 |
2 |
Single-ended |
1 |
Sss11 |
Ssd12 |
Ssc12 |
Differential |
2 |
Sds21 |
Sdd22 |
Sdc22 |
Common |
2 |
Scs21 |
Scd22 |
Scc22 |
The mixed mode S-parameters for balanced-balanced devices (Bal-Bal)
Logical port mode |
Stimulus |
Differential |
Common |
||
Receiver |
Logical port number |
1 |
2 |
1 |
2 |
Differential |
1 |
Sdd11 |
Sdd12 |
Sdc11 |
Sdc12 |
2 |
Sdd21 |
Sdd22 |
Sdc21 |
Sdc22 |
|
Common |
1 |
Scd11 |
Scd12 |
Scc11 |
Scc12 |
2 |
Scd21 |
Scd22 |
Scc21 |
Scc22 |
|
The mixed mode S-parameters for single-ended – single-ended – balanced devices (SE-SE-Bal)
Logical port mode |
Stimulus |
Single-ended |
Differential |
Common |
|
Response |
Logical port number |
1 |
2 |
3 |
3 |
Single-ended |
1 |
Sss11 |
Sss12 |
Ssd13 |
Ssc13 |
Single-ended |
2 |
Sss21 |
Sss22 |
Ssd23 |
Ssc23 |
Differential |
3 |
Sds31 |
Sds32 |
Sdd33 |
Sdc33 |
Common |
3 |
Scs31 |
Scs32 |
Scd33 |
Scc33 |
The mixed mode S-parameters for balanced devices (Bal)
Logical port mode |
Stimulus |
Differential |
Common |
Response |
Logical port number |
1 |
1 |
Differential |
1 |
Sdd11 |
Sdc11 |
Common |
2 |
Scd1 |
Scc11 |
The balanced devices measurement results can be also represented as imbalance parameters. The figures below shows the functions of imbalance parameter calculation for the following three types of balanced devices. Note that imbalance parameters are calculated only using data of single-ended devices.
Imbalance= - Sba/Sca
Single ended - Balanced devices (Se-Bal)
Imbalance1= - (Sac-Sad)/(Scb-Sbd)
Imbalance2= - (Sca-Scb)/(Sda-Sdb)
Balanced - Balanced devices (Bal-Bal)
Imbalance1= - (Sac-Sad)/(Sbc-Sbd)
Imbalance2= - (Sca-Scb)/(Sda-Sdb)
Imbalance3= - Sca/Sda
Imbalance4= - Scb/Sdb
Single ended - Single ended - Balanced devices (Se-Se-Bal)
Imbalance parameters
A convenient way of evaluating balanced devices parameters is their representation using common mode rejection ratio (CMRR). This ratio is calculated after balance-unbalance conversion of mixed mode S-parameters.
For single-ended - balanced devices:
CMRR1 = Sds21 / Scs21
CMRR2 = Ssd12 / Ssc12
For balanced - balanced devices:
CMRR = Sdd21 / Scc21
For single-ended – single-ended – balanced devices:
CMRR1 = Sds31 / Scs31
CMRR2 = Sds32 / Scs32
