Installation guide

Troubleshooting
Troubleshooting Unlevels and the RF Path
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Troubleshooting Unlevels and the RF Path
Depending on the signal generator’s frequency range and option selection, there are either one or two output
boards used in the RF path:
• Signal generators with Option 501, 502, 503, 504, and Option UNJ contain either the:
— A13 Output (Option 501, 502, 503, 504 or Option UNJ)
— or the A13 Output (Option UNB)
• Signal generators with Option 506 contain both the:
— A13 Output (Option UNB)
— and the A14 Extended Frequency Output (Option 506)
On the output boards, a leveled output power is obtained by comparing a detected voltage with a reference
voltage. The reference voltage is generated using DACs on the output boards. The detected voltage is
generated by coupling off a portion of the RF output signal and converting it to dc using detector diodes. When
the reference and detected levels are the same, the integrated output level remains constant. When the
reference and detected levels are not the same, the integrator output ramps either up or down to increase or
decrease the detected level. If the integrator can not achieve a match between the detected voltage and the
reference voltage, an unleveled annunciator is displayed.
Each output board has an Automatic Leveling Control (ALC) circuit which consists of a detector and two
modulator diodes. The A13 Output controls the power level for frequencies 4 GHz and below
and the A14 Extended Frequency Output (Option 506) controls the power level for frequencies above
4GHz and ≤ 6GHz.
The RF path must provide a minimum power level to the ALC loop in order for the ALC loop to work properly
and this minimum required power is slightly higher than the maximum-leveled power.