VNA Concepts and Features
R&S
®
ZNL/ZNLE
222
User Manual 1178.5966.02 ─ 07
8.3.3.1
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
impedances.
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
according to:
ii
ii
ii
i
ii
Z
S
S
Z
Y
/
1
1
1
1
0
The transmission parameters are calculated according to:
99
...,
,
1
,
,
,
/
1
2
0
0
0
0
j
i
j
i
Z
Z
Z
S
Z
Z
S
Y
ij
j
i
ij
j
i
ij
ij
Examples:
●
Y
11
is the input admittance of a 2-port DUT that is terminated at its output with the
reference impedance Z
0
(matched-circuit admittance measured in a forward reflec-
tion measurement).
You can also read the converted admittances in a reflection coefficient measurement
from the inverted Smith chart.
8.3.3.2
Y-Parameters
The Y-parameters describe the admittances of a DUT with output ports terminated in a
short circuit (voltage = 0). The analyzer provides the full set of Y-parameters including
the transfer admittances (i.e. the complete n x n Y-matrix for an n port DUT).
This means that Y-parameters can be used as an alternative to S-parameters (or Z-
parameters) to characterize a linear n-port network completely.
Measurement Results
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