Concepts and Features
R&S
®
ZNA
106
User Manual 1178.6462.02 ─ 12
5.3.3
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)
5.3.3.1
Converted Impedances
The converted impedance parameters Z
ij
(1 ≤i,j ≤n) describe the input impedances of
an n-port DUT with fully matched outputs. The analyzer converts a single measured S-
parameter S
ij
to determine the corresponding converted impedance, under the
assumption that each of the other ports is terminated with its respective reference
impedance Z
0k
(matched-circuit parameters). As a result, converted impedances can-
not completely describe general n-port DUTs.
The extension of the impedances to more ports and mixed mode measurements is
analogous to S-parameters. Z
dd44
is the differential mode input impedance at port 4 of a
DUT that is terminated at its other ports with the reference impedance Z
0
.
are defined as the inverse of the converted impedances.
Reflection Impedance
The converted impedance Z
ii
(1 ≤ i ≤n) describes the input impedance at port i of the
DUT.
U
0
I
1
U
1
Z
0i
Z
ii
Example:
For a 2-port DUT that is terminated at its output with the reference impedance Z
02
, Z
11
is the input impedance (matched-circuit impedance measured in a forward reflection
measurement).
A converted impedance Z
11
completely describes a one-port DUT.
The calculation formula of the converted reflection impedances Z
ii
depends on the
waveguide circuit theory according to which
Measurement Results
