System Overview
R&S
®
ZVA
77
Getting Started 1145.1090.62 ─ 13
Meaning of squared amplitudes
The squared amplitudes of the incident and outgoing waves and of the matrix elements
have a simple meaning:
Table 3-1: Squared S-parameters
|a
1
|
2
Available incident power at the input of a two-port (= the power pro-
vided by a generator with a source impedance equal to the refer-
ence impedance Z
0
)
|a
2
|
2
Available incident power at the output
|b
1
|
2
Reflected power at the input of a two-port
|b
2
|
2
Reflected power at the output
10*log|S
11
|
2
(= 20*log|S
11
|)
Reflection loss at the input
10*log|S
22
|
2
Reflection loss at the output
10*log|S
21
|
2
Insertion loss at the input
10*log|S
12
|
2
Insertion loss at the output
3.3.1.1
Multiport S-Parameters
The multiport S-parameters extend the standard 2-port S-parameters to a larger num-
ber of incoming 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 a
i
denotes the incident and b
i
the outgoing wave at DUT port i = 1 to 4, and the
S-parameters are expressed as S
ij
(i,j = 1 to 4).
The parameters conisdered so far are referred to as single-ended S-parameters. The
S-parameter description can also be used to describe different propagation modes of
the waves at the output and input ports. This results in so-called mixed mode S-param-
eters. The analyzer measures either single-ended or mixed mode S-parameters.
3.3.2 Impedance Parameters
An impedance is the complex ratio between a voltage and a current. The analyzer pro-
vides two independent sets of impedance parameters:
●
Converted impedances (each impedance parameter is obtained from a single S-
parameter)
●
Z-parameters (complete description of the n-port DUT)
Measured Quantities
