R&S ZNB Series User Manual page 126

®
R&S ZNB/ZNBT
The figure above is sufficient for the definition of S-parameters but does not necessa-
rily show the complete signal flow. In fact, if the source and load ports are not ideally
matched, part of the transmitted waves are reflected off the receiver ports. An addi-
tional a
reverse measurements. The 7-term calibration types Txx take these additional contri-
butions into account.
The scattering matrix links the incident waves a
according to the following linear equation:
Meaning of 2-port S-parameters
The four 2-port S-parameters can be interpreted as follows:
●
S
b
S
●
S
wave b
S
●
S
wave b
S
●
S
incident wave a
S
Meaning of squared amplitudes
The squared amplitudes of the incident and outgoing waves and of the matrix elements
have a simple meaning:
User Manual 1173.9163.02 ─ 62
contribution occurs in forward measurements, and an a
2
is the reflection coefficient of DUT port 1, i.e. the ratio between outgoing wave
11
and incident wave a
1 1
= b / a , if |a | > 0 and a
11 1 1 1
is the forward transmission coefficient, defined as the ratio between outgoing
21
and incident wave a
2
= b / a , if |a | > 0 and a
21 2 1 1
is the reverse transmission coefficient, defined as the ratio between outgoing
12
and incident wave a
1
= b / a , if |a | > 0 and a
12 1 2 2
is the reflection coefficient of port 2, i.e. the ratio between outgoing wave b
22
in a forward measurement with matched DUT port 1:
2
= b / a , if |a | > 0 and a
22 2 2 2
, a
1
in a forward measurement with matched DUT port 2:
= 0
2
in a forward measurement with matched DUT port 2:
1
= 0
2
in a forward measurement with matched DUT port 1:
2
= 0
1
= 0
1
Concepts and features
Measurement results
contribution occurs in
1
to the outgoing waves b
2
, b
1 2
and
2
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