VNA Concepts and Features
R&S
®
ZNL/ZNLE
219
User Manual 1178.5966.02 ─ 07
Table 8-3: 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
8.3.2
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 an n-port DUT)
8.3.2.1
Converted Impedances
The converted impedance parameters describe the input impedances of a DUT with
fully matched outputs. In the figures below the indices i and j number the analyzer/DUT
ports, Z
0i
is the reference impedance at the DUT port i.
The analyzer converts a single measured S-parameter to determine the corresponding
converted impedance. As a result, converted Z-parameters cannot completely describe
general n-port DUTs:
●
A reflection parameter Z
ii
completely describes a one-port DUT. For n-port DUTs
(n>1), the reflection parameters Z
ii
describe the input impedances at ports i (i = 1 to
n) under the condition that each of the other ports is terminated with its reference
impedance (matched-circuit parameters).
●
A two-port transmission parameter Z
ij
(i ≠ j) can describe a pure serial impedance
between the two ports.
Relation with S-parameters
The converted impedances Z
ii
are calculated from the reflection S-parameters S
ii
according to:
Measurement Results
www.allice.de
Allice Messtechnik GmbH
