Rohde & Schwarz R&S ZNB - Page 117

Concepts and Features
R&S
®
ZNB/ZNBT
117User Manual 1173.9163.02 ─ 53
Meaning of squared amplitudes
The squared amplitudes of the incident and outgoing waves and of the matrix elements
have a simple meaning:
Table 5-3: 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
5.3.1.1 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
SSSS
SSSS
SSSS
SSSS
b
b
b
b
4
3
2
1
44434241
34333231
24232221
14131211
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.
5.3.1.2 Redefined S-Parameters
The analyzer firmware allows you to redefine the physical VNA ports, simply by speci-
fying:
●
a reference receiver ("a wave")
●
a measurement receiver ("b wave")
●
a generator ("Source" VNA or external generator port)
As a consequence, the measured S-parameters and other wave quantities are also
redefined.
Measurement Results