Operating Information
2
N432A User’s Guide
83
Therefore:
The left side of the equation can be replaced by the factor M as follows:
This cannot be directly solved for
Γ
s
because it is a complex quantity. To
solve for
Γ
s
, additional values of load reflection coefficient are required
with a phase difference of approximately 120°. However, an approximate
solution using two values of
Γ
L
can give adequately accurate results
provided the phase angle of the source is within
±
40° of 0° or
±
180°.
The following procedure describes how to measure the VSWR of a source.
1
Preset the N432A to its default state by pressing
.
2
Connect a thermistor sensor to the channel A input connector of the
N432A.
3
A message will appear to inform you of the current bridge resistance
value and require you to select a new resistance value or reconfirm the
current resistance value. Use the softkeys to select a value of 200
Ω
.
4
You will then be prompted for confirmation to proceed with zeroing.
Press
Confirm
to proceed.
5
Another message will appear, prompting you to confirm whether the
sensor has been disconnected from the RF source. Press
Confirm
once
you have verified that there is no RF source connected.
6
Zeroing will start automatically. The Zeroing pop- up message will be
displayed during the zeroing process.
7
Set up the following connections shown in
. The network
analyzer is used to measure the S
11
parameter which is equivalent to
the reflection coefficient of the thermistor sensor.
P
1
P
2
------
1
Γ
2
2
–
(
)
1
Γ
1
2
–
(
)
--------------------------
1
Γ
s
Γ
2
–
2
1
Γ
s
Γ
1
–
2
---------------------------
=
M
1
Γ
s
Γ
2
–
1
Γ
s
Γ
1
–
------------------------
=
Содержание N432A
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