Rohde & Schwarz ZVA8 - Page 78

System Overview
R&S
®
ZVA
78Quick Start Guide 1145.1090.62 ─ 10
●
Z
12
is the reverse transfer impedance, defined as the ratio of the voltage V
1
to the
current I
2
(reverse measurement with open input, I
1
= 0).
●
Z
22
is the output impedance, defined as the ratio of the voltage V
2
to the current I
2
,
measured at port 2 (reverse measurement with open input, I
1
= 0).
Z-parameters can be easily extended to describe circuits with more than two ports or
several modes of propagation.
3.3.2.4 Admittance Parameters
An admittance is the complex ratio between a current and a voltage. The analyzer pro-
vides two independent sets of admittance parameters:
●
Converted admittances (each admittance parameter is obtained from a single S-
parameter)
●
Y-parameters (complete description of the n-port DUT)
3.3.2.5 Converted Admittances
The converted admittance parameters describe the input admittances of a DUT with fully
matched outputs. The converted admittances are the inverse of the converted impedan-
ces.
The analyzer converts a single measured S-parameter to determine the corresponding
converted admittance. As a result, converted Y-parameters cannot completely describe
general n-port DUTs:
●
A reflection parameter Y
ii
completely describes a one-port DUT. For n-port DUTs
(n>1) the reflection parameters Y
ii
describe the input admittances 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 Y
ij
(I ≠ j) can describe a pure serial impedance
between the two ports.
Relation with S-parameters
The converted admittances Y
ii
are calculated from the reflection S-parameters S
ii
accord-
ing to:
ii
ii
ii
i
ii
Z
S
S
Z
Y /1
1
11
0




The transmission parameters are calculated according to:
 
99...,,1,,,/1
2
0000


 jijiZ
ZZSZZ
S
Y
ij
jiijji
ij
ij
Measured Quantities