Troubleshooting Unlevels; Troubleshoot And Correct Any Unlock Problems Before Troubleshooting Unleveled Problems - Agilent Technologies PSG Series Service Manual

Troubleshooting Unlevels

A leveled output power is obtained comparing a detected voltage with a reference voltage. The reference
voltage is generated using DACs on the A10 ALC and 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 detected and reference 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 get the detected voltage and the reference voltage to match, an unleveled annunciator is
displayed.
The Automatic Leveling Circuit (ALC) uses two detectors and two modulator diodes. The A23 Low Band
Coupler/Detector is used for frequencies 2 GHz and below. The A25 Highband Coupler/Detector is used for all
frequencies above 2 GHz. The modulator in the A23 Low Band Coupler/Detector is used to control the RF
amplitude for frequencies 3.2 GHz and below. The modulator in the A30 Modulation Filter is used to control
the amplitude for frequencies above 3.2 GHz.
The RF path must provide a minimum power level to the ALC loop for the ALC loop to work properly. The
minimum power required is slightly higher than the maximum leveled power. The first step to
troubleshooting a leveling problem is to verify the RF path power level.
Troubleshoot and correct any unlock problems before troubleshooting unleveled
problems.
If the unleveled annunciator is on:
1. Verify the signal generator's amplitude is not set higher than the maximum level specified on the data
sheet. Verify that the signal generator's RF output is terminated into 50 ohms. If the unleveled indication
turns off after resetting the amplitude or terminating the RF output into 50 ohms, the signal generator is
operating correctly. If the unleveled indicator remains on, proceed to step 2.
2. Using a spectrum analyzer check the RF signal level at the RF output connector.
a. Signal generator and spectrum analyzer setup:
Signal Generator:
• Turn ALC Off
• Set Amplitude to 30 dBm
• Turn Modulation Off
• Turn RF On
• Set Sweep to Frequency
• Set Sweep Type to Step
• Set Start Frequency to 250 kHz
• Set Stop Frequency to 3.2 GHz
• Set Number of Points to 500
Spectrum Analyzer:
• Set Start Frequency to 225 kHz
Troubleshooting
Troubleshooting Unlevels
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