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Chapter 10 191
Troubleshooting
RF Output Power Problems
Figure 10-2 Reverse Power Solution
Compared to the original configuration, the ALC level is 10 dB higher while the attenuator reduces the LO
feedthrough (and the RF output of the signal generator) by 10 dB. Using the attenuated configuration, the
detector is exposed to a +2 dBm desired signal versus the
-15 dBm undesired LO feedthrough. This 17 dB difference between desired and undesired energy results in
a maximum 0.1 dB shift in the signal generator’s RF output level.
RF LEVEL
CONTROL
SIGNAL GENERATOR
OUTPUT CONTROL
MIXER
LO
IF
ALC LEVEL/
DETECTOR
MEASURES
+2 dBm
ALC LEVEL
DETECTOR
MEASURES
- 15 dBm
REVERSE
POWER
LO FEEDTHRU
= - 5 dBm
RF INPUT
= - 8 dBm
LO LEVEL
= +10 dBm
10 dB
ATTEN
RF OUTPUT
= +2 dBm