VBLO Mixer Bias

The purpose of this calibration is to optimally set the LBOUT/HBOUT:VBLO_DAC on the output board for use in the digital mode of operation. The LBOUT/HBOUT: VBLO_DAC on the output board is used to control the bias voltage to the internal I/Q modulator mixers. The LBOUT/HBOUT: VBLO_DAC primarily is used to adjust the mixer bias for optimum I/Q modulation linearity (low intermodulation distortion and I/Q modulation errors), but it has a secondary influence on the mixer gain. The goal of this calibration is to have sufficient power through the I/Q modulator to perform the desired modulation (have enough UUT output power available), while minimizing intermodulation distortion when digital modulation is in use.

For frequencies > 4 GHz, default DAC values are used.

Required Test Equipment

Test Equipment	Recommended Model
50 ohm Termination	909A Opt 012

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.

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.