R&S ZVB - Page 62

R&S
®
ZVA / R&S
®
ZVB / R&S
®
ZVT System Overview
Measured Quantities
Operating Manual 1145.1084.12 – 30 47
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:
The transmission parameters are calculated according to:
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 reflection measurement).
 The extension of the admittances to more ports and mixed mode measurements is analogous to
S-parameters. Y
dd44
is the differential mode input admittance at port 4 of a DUT that is terminated
at its other ports with the reference impedance Z
0
. See More Admittances for detailed information.
You can also read the converted admittances in a reflection coefficient measurement from the
inverted Smith chart.
Y-Parameters
The Y-parameters describe the admittances of a DUT with output ports terminated in a short circuit (V =
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) in order
to completely characterize a linear n-port network.
2-Port Y-Parameters
In analogy to S-parameters, Y-parameters are expressed as Y
<out>< in>
, where <out> and <in> denote the
output and input port numbers of the DUT.
In analogy to Z-parameters, the Y-parameters for a two-port are based on a circuit model that can be