Fluke 9640A Series, Instruction Manual

Page: 238 / 324

9640A
Instruction Manual
5-48
VSWR Test — 75
Ω
(Optional)
Equipment Required for this Test:
•
Signal Generator, 75
Ω
•
Spectrum Analyzer
•
75
Ω
to 50
Ω
impedance-matching pad
•
75
Ω
directional bridge
•
Precision 75
Ω
Open termination
•
Precision 75
Ω
Short termination
•
75
Ω
Leveling Head (supplied with UUT)
Use the following test to verify the UUT’s output VSWR using a directional bridge and a
spectrum analyzer.
1.
Connect the REF FREQUENCY OUTPUT (rear panel) from the UUT to the
spectrum analyzer and signal generator external reference inputs using a BNC tee and
BNC male – male cable assemblies. Set the spectrum analyzer and signal generator
for external frequency reference.
2. On the UUT enable the REF FREQUENCY OUTPUT at 10 MHz. Ensure the
spectrum analyzer and signal generator external reference frequency inputs are
enabled for input at 10 MHz.
3. Connect the signal generator RF output to the input port of the directional bridge.
Connect the directional bridge coupled (output) port to the spectrum analyzer input
using a 75
Ω
to 50
Ω
impedance-matching pad. See Figure 5-13.
Note
In order to determine the reference level setting of the spectrum analyzer,
the UUT must initially be connected to the directional bridge.
4. Connect the UUT to the test port of the directional bridge.
5. Set the spectrum analyzer as follows:
PRESET
EXT REF
On
REF LVL +10 dBm
FREQ 500 MHz
SPAN Zero Span
6. Set the signal generator as follows:
Frequency 500.00001
MHz
Amplitude 0 dBm
Output On
7. Set the UUT as follows:
Frequency 500 MHz
Level +7 dBm
Output
OPER
8. Adjust the spectrum analyzer reference level to place the displayed trace
approximately 3 dB below the reference level line.
9. Set the UUT to
STBY
and disconnect it from the directional bridge. Connect the open
(75 Ω ) termination to the directional bridge test port.