Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide 151
Troubleshooting
Amplitude Modulation Issues (Option UNT)
AM Calibration
If the failure persists after the adjustment replace the A3 RF assembly.
3.2 GHz to Max Frequency
Since the amplitude modulation generator and the modulator used for
amplitude modulation in this frequency range are not contained on the same
assembly the issue will need to be isolated to the assembly causing the
problem. Use the following procedure to isolate the problem:
1. Return the instrument to a known state by pressing Preset.
2. Tune the instrument to a frequency at or above 3.2 GHz that is having the
problem by pressing FREQ, <frequency>.
3. Turn the RF on by pressing RF On/Off so that the LED below it comes on.
4. Set the signal level to 0 dBm by pressing AMPTD, 0 dBm.
5. Turn AM on by pressing AM, AM On.
6. Set the AM Type to exponential by setting AM Type, EXP.
7. Set the AM Depth to 40 dB by pressing AM Depth, 40 dB.
8. Verify that the AM Rate is set to 400 Hz by pressing More, Setup AM
Source, AM Rate, 400 Hz.
9. Connect the RF Output to a spectrum analyzer with the following settings:
— Center Frequency = Signal Generator Frequency
— Span = 0 Hz
— Reference Level = 0.0 dBm
— Sweep Time = 10.0 ms
If the amplitude modulation was working properly there would be a
sinewave signal on the spectrum analyzer with a peak-to-peak amplitude
of 40 dB.
10.Referring to Figure 6-8, connect an oscilloscope to Test Point 40 (TP 40)
on the A7A1 Microwave ALC Control board assembly.
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