Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 140 / 813

Measured Quantities R&S
®
ZVA/ZVB/ZVT
1145.1084.12 3.30 E-1
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 short-circuit admittances 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 Short-Circuit 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 open-circuit Z-parameters, the short-circuit Y-parameters for a two-port are based on a
circuit model that can be expressed with two linear equations:
2 22 1 21 2
2 12 1 11 1
V Y V Y I
V Y V Y I
+ =
+ =
Meaning of Y-parameters
The four 2-port Y-parameters can be interpreted as follows:
•
Y
11
is the input admittance, defined as the ratio of the current I
1
to the voltage V
1
, measured at
port 1 (forward measurement with output terminated in a short circuit, V
2
= 0).
•
Y
21
is the forward transfer admittance, defined as the ratio of the current I
2
to the voltage V
1
(forward measurement with output terminated in a short circuit, V
2
= 0).
•
Y
12
is the reverse transfer admittance, defined as the ratio of the current I
1
to the voltage V
2
(reverse measurement with input terminated in a short circuit, V
1
= 0).
•
Y
22
is the output admittance, defined as the ratio of the current I
2
to the voltage V
2
, measured at
port 2 (reverse measurement with input terminated in a short circuit, V
1
= 0).
Y-parameters can be easily extended to describe circuits with more than two ports or several modes of
propagation.
Wave Quantities and Ratios
The elements of the S-, Z- and Y-matrices represent fixed ratios of complex wave amplitudes. As long