Rohde & Schwarz ZVA8 - Impedance Parameters

System Overview
R&S
®
ZVA
76Quick Start Guide 1145.1090.62 ─ 10
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)
3.3.2.1 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
accord-
ing to:
ii
ii
iii
S
S
ZZ



1
1
0
The transmission parameters are calculated according to:
 
,,2
00
00
jiZZ
S
ZZ
Z
ji
ij
ji
ij



The converted admittances are defined as the inverse of the impedances.
Measured Quantities