Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 139 / 813

R&S
®
ZVA/ZVB/ZVT Measured Quantities
1145.1084.12 3.29 E-1
I
1
DUT
I
2
+
V
1
V
2
Z
12
I
2
Z
21
I
1
Z
11
Z
22
2 22 1 21 2
2 12 1 11 1
I Z I Z V
I Z I Z V
+ =
+ =
Meaning of Z-parameters
The four 2-port open-circuit Z-parameters can be interpreted as follows:
•
Z
11
is the input impedance, defined as the ratio of the voltage V
1
to the current I
1
, measured at
port 1 (forward measurement with open output, I
2
= 0).
•
Z
21
is the forward transfer impedance, defined as the ratio of the voltage V
2
to the current I
1
(forward measurement with open output, I
2
= 0).
•
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.
Admittance Parameters
An admittance is the complex ratio between a current and a voltage. The analyzer provides two
independent sets of admittance parameters, essentially based on different n-port circuit models:
•
Matched-circuit admittances, converted from S-parameters
•
Short-circuit Y-parameters
Converted Admittances
The converted (matched-circuit) admittances describe the admittances of a DUT that is terminated at its
outputs with the reference impedance values Z
0i
displayed in the Port Configuration dialog. i numbers
the analyzer/DUT port. The analyzer converts the measured S-parameters to determine the matched-
circuit admittances. The converted admittances are the inverse of the converted impedances. The
reflection parameters are calculated according to:
, / 1
1
1 1
0
ii
ii
ii
i
ii
Z
S
S
Z
Y
=
+
−
=
where i numbers the analyzer/DUT port. 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