R&S ZNLE Series - Impedance Parameters

VNA concepts and features
R&S
®
ZNL/ZNLE
219User Manual 1178.5966.02 ─ 20
9.3.3 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)
9.3.3.1 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 Converted admittances 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 Reference impedances are calculated.
Measurement results