Tektronix WFM700 Series, Service Manual

Page: 64 / 194

Performance Verification
2- 32
WFM700 Series Waveform Monitors Service Manual
This test checks the signal return loss. Performance is checked indirectly.
Performance Requirement.
This test verifies performance characteristics and is
listed in the test record.
1. Install the 50
8
N-to-BNC adapter on the RF generator output.
2. Connect the RF generator output to the input port of the Return Loss Bridge
using a 50
8
cable.
3.
Connect the output of the Return Loss Bridge to the 50
8
input of the test
oscilloscope using a 50
8
cable. Do not connect the test port of the Bridge at
this time.
4. Set the RF generator as follows:
Frequency 900 MHz
Phase Modulation OFF
Frequency Modulation OFF
Output Power +7.0 dBm
RF Output ON
5.
Adjust the test oscilloscope to obtain a stable display of the 900 MHz sine
wave from the RF generator.
6. Measure the amplitude of the signal on the test oscilloscope. Note this
measurement as the reference level.
7. Connect the test port of the Return Loss Bridge directly to INPUT A . Do not
use any cables or adapters.
8. Press the INPUT button and select Input A .
9.
Measure the amplitude of the signal on the test oscilloscope. Note this as the
A Reflection level.
10. Calculate the return loss with the formula below using the measured values
from steps 6 and 9.
Input A Return Loss
20
log
10
Æ
Reference
A Reflection
É
11.
CHECK that the calculated return loss is >25 dB for Input A.
Input Return Loss