Concepts and features
R&S
®
ZND
110
User Manual 1173.9557.02 ─ 61
Meaning of squared amplitudes
The squared amplitudes of the incident and outgoing waves and of the matrix elements
have a simple meaning:
Table 4-3: Squared S-parameters
|a
i
|
2
Available incident power (= the power provided by a generator with
a source impedance equal to the reference impedance Z
0
) at DUT
port i=1,2
|b
i
|
2
Reflected power at DUT port i=1,2
10 log|S
ii
|
2
= 20 log|S
ii
|
Reflection loss at DUT port i=1,2
10 log|S
21
|
2
= 20 log|S
21
|
Insertion loss of forward transmission
10 log|S
12
|
2
= 20 log|S
12
|
Insertion loss of reverse transmission
4.3.1.1
Multiport S-parameters
The multiport S-parameters extend the standard 2-port S-parameters to a larger num-
ber of incident and outgoing waves. For a 4-port DUT,
a
a
a
a
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
b
b
b
b
4
3
2
1
44
43
42
41
34
33
32
31
24
23
22
21
14
13
12
11
4
3
2
1
where again a
i
(i = 1 to 4) denote the incident, b
i
(i = 1 to 4) denote the outgoing waves,
and the S-parameters are expressed as S
ij
(i,j = 1 to 4).
The indices of the S-parameters described so far number the output and input ports of
a DUT; the parameters are referred to as single-ended S-parameters. The S-parameter
description can also be used to differentiate between different propagation modes of
the waves at the output and input ports. This results in the so-called mixed mode S-
parameters. The analyzer measures either single-ended or mixed mode S-parameters.
4.3.2
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.
Measurement results
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