Agilent Technologies 4395A - Page 390

Network
Measurement
Basics
S-P
arameter Denition
Test
Set Description
Direction
S
11
b
1
a
1
j
a
2
=0
Input
reection
Coecient
FWD
S
21
b
2
a
1
j
a
2
=0
F
orward
gain
FWD
S
12
b
1
a
2
j
a
1
=0
Reverse
gain REV
S
22
b
2
a
2
j
a
1
=0
Output reection
coecient REV
Conversion
Function
This
function
converts
the
measured
reection
or transmission
data to
the equivalent
complex
impedance
(Z)
or
admittance
(Y)
values
. This
is not
the same
as a
two-port
Y
or
Z
parameter
conversion,
as
only
the
measured
parameter
is used
in the
equations.
Two simple
one-port
conversions
are
available
,
depending
on
the
measurement
conguration.
An
S
11
or
S
22
trace
measured
as
reection
can be
converted to
an equivalent
parallel
impedance
or
admittance
using
the model
and equations
shown in
Figure
A
-6
.
Figure
A
-6.
Reection
Impedance
and
A
dmittance
Conversions
In
a
transmission
measurement,
the
data
can
be
converted
to
its
equivalent
series
impedance or
admittance
using
the
model
and
equations
shown
in
Figure
A
-7
.
Figure A-7. Transmission Impedance and Admittance Conversions
Avoid using Smith chart, SWR, and delay formats for displaying Z and Y conversions,as
these formats are not easily interpreted. Marker values are impedance values in  units for Z
conversions, or admittance values in S units for Y conversions in any format.
A-14 Basic Measurement Theory