Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide 249
Baseband Generators
A2 Vector BBG Assembly Troubleshooting
4. Tune the instrument to a frequency that exhibits the power level issue
when using digital modulation.
5. Connect a spectrum analyzer to A3 J2004.
6. Configure the spectrum analyzer with the following settings:
— Center Frequency = Frequency of signal source
— Span = 10 MHz
— Reference Level = +10 dBm
7. Turn the digital modulation path on by pressing I/Q, I/Q On.
8. The power level of the signal at A3 J2004 should be at a fixed level of 0
dBm, +/-6dB.
— If the power level measured is not 0 dBm, +/-6 dBm, replace the A3
RF assembly since there are no adjustments for this power level.
— If the power level measured is 0 dBm, +/-6 dB, proceed to step 9.
9. Referring to Figure 12-3, remove W8.
10.Connect the spectrum analyzer to the RF output connector of the
instrument.
11.Connect a short RF cable between A3 J2004 and A3 J2003.
12.Set the power level to 0 dBm by pressing AMPTD, 0 dBm.
13.The power level of the signal on the spectrum analyzer should measure 0
dBm, +/-1 dB plus the loss of any cables and connector used.
— If the power level is not correct, the problem is with the A3 RF
assembly or an IQ related adjustment for it. Replace the cables that
were removed and run all the “I/Q Related Adjustments” discussed
later in this chapter. If this does not resolve the issue replace the A3
RF assembly.
— If the power level is correct, the problem is with the A2 Vector BBG
assembly. Replace the cables that were removed and run all the
“I/Q Related Adjustments” discussed later in this chapter. If this
does not resolve the issue replace the A2 Vector BBG assembly.
Unleveled Conditions
If there are any unlevel conditions that only exist when using digital modulation
see “I/Q Modulator Unlevel” in Chapter 6, “Troubleshooting”
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