46 Keysight Agile Signal Generator Service Guide
Troubleshooting
Troubleshooting Unlevels
An Automatic Leveling Control (ALC) loop on the A20 Output Leveling Module
provides leveled output power. The ALC loop is a feedback control system that
monitors RF power and maintains power at the user-selected level. The RF
path must provide a minimum power level to the ALC loop for the ALC loop to
work correctly. The minimum required power is slightly higher than the
instrument maximum power level.
A leveled output power is obtained by comparing a detected voltage with a
reference voltage. The detected voltage is generated by coupling off a portion
of the RF output signal and converting it to a dc voltage using detector diodes.
The reference voltage is generated using calibrated DAC’s. When the reference
and detected levels are not the same, the ALC integrator output ramps up or
down, to increase or decrease the detected level. If the integrator cannot
achieve a match between the detected and reference voltages an unleveled
annunciator is displayed.
1. Run a complete self test.
Press: Utility > Instrument Info > Self Test > Run Complete Self Test.
2. Measure the output power at the RF connector.
3. Check the measured output power level against the values in Table 1-2.
The output power values shown in this table might not apply to your specific signal generator
configuration. Refer to the current data sheet for the latest power level data.
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