Prelevel

Use this calibration to optimally set the prelevel reference DAC on the output board for use in the digital mode of operation.

The prelevel reference DAC on the output board is used to control the RF power level that is incident upon the I/Q modulator. It does this by setting the control point for the prelevel loop. The loop has a detector on an output of the I/Q modulator, its drive circuitry is also on the output board, but its RF modulator that it controls is on the Frac-N/synthesizer board. The goal of this calibration is to have sufficient power available at the I/Q modulator to perform the desired modulation (and have enough UUT output power available), while minimizing intermodulation distortion when digital modulation is in use.

For frequencies up to 4 GHz, a power meter measures the signal level at the input of the Output module (at the rear panel coherent carrier connector). For frequencies above 4 GHz, the ABUS is used to monitor the signal level on the high band output module.

Required Test Equipment

Test Equipment	Recommended Model	Alternate Model
Power Meter (Required only for E4438C)	N1914B	N1914A¹ N1913A N1913B E4418A E4418B E4419A E4419B
Power Sensor (Required only for E4438C)	N8482A	E9304A E9304A H18 N8482A CFT 8482A²
50 ohm Termination	909A Opt 012

Power meter N1914A with serial numbers ranging between MY00000000—MY53040007 require Service Note 07 to be applied for measurement repeatability. Please have this service note applied or verify it was applied before using this power meter. The affected service note is N1914A-07.
Not allowed for the E4438C with Option 506. The dynamic frequency range of this sensor is insufficient for this model.

Connections and Setup Procedures

All test equipment requires a 30 minute warmup period to ensure accurate performance.
In the following adjustment setup, cables are designated as solid lines and direct connections are designated as dashed lines.

Connect all test equipment as shown.
Connect GPIB cables to all GPIB-controlled test equipment.
While performing this adjustment, follow all instructions on the controller display.

Power Meter Zero and Cal Setup for E4438C

Connection for E4428C

In Case of Difficulty

If this adjustment fails, perform the following steps in order:

Check the equipment setup (see above). If the setup is incorrect, make the necessary corrections and rerun the adjustment.
If this adjustment fails with the equipment set up properly, refer to the troubleshooting section of the signal generator's service guide. If you do not have a printed copy of the service guide (Option OBW), one is available either on the CD-ROM that came with your signal generator shipment or on the Keysight Website.
If you cannot correct the problem using the troubleshooting procedures in the Service Guide, obtain service from Keysight Technologies. Refer to Contacting Keysight Technologies.