Agilent Technologies E4438C - Manual (Page 120)

Adjustments
Prelevel Calibration
4-28
Prelevel Calibration
Description
This calibration adjusts the PRE LEVEL REF DAC on the A13 Output. This DAC is used to control the RF
power level that is incident upon the I/Q modulator by setting the control point for the pre-level loop. The
pre-level loop detector is on the output of the I/Q modulator, its drive circuitry on the A13 Output, and its RF
modulator on the A17 Synthesizer (Option 501, 502, 503, 504). This calibration ensures that there will be
sufficient power available at the I/Q modulator to perform the desired modulation while minimizing
intermodulation distortion when the digital modulation is activated. The signal generator is set to a
frequency and the auxiliary output amplitude level is adjusted using the PRE LEVEL DAC to within the
specified tolerance of the desired value. This process is repeated for all the frequencies in the I/Q modulator
index array. The results are then stored in the signal generator’s firmware.
Required Test Equipment
• Agilent E4418B E-Series power meter
• Agilent E9304A E-Series power sensor
Procedure
Figure 4-21 Prelevel Calibration Setup
1. Connect the equipment as shown above.
2. Preset all of the equipment.
3. Follow the instructions as they appear on the controller’s display.