Burst Modulator

This calibration is used to adjust the bias modulator circuitry to provide an accurate logarithmic drop in power level for a linear input voltage. When correctly adjusted, a one volt signal on the input will result in a 40 dB drop in power level. The adjustment involves choosing the correct values for three DACs located in the burst modulator circuit. The adjustment is repeated at several frequencies and the results are stored in calibration arrays corresponding to each DAC.

The BURST MOD OFFSET DAC sets the initial current level through the burst modulator diode.
The BURST MODLIN DAC is used to calibrate the input voltage level to the burst driver circuit.
The BURST DRIVER BIAS/GAIN DAC sets the breakpoint at which the modulator switches from a logarithmic to a linear transfer function (”knee”).

Required Test Equipment

Test Equipment	Recommended Model	Alternate Model
Spectrum Analyzer	N9030B Opt 5xx¹	N9030A Opt 5xx¹ E444xA² Opt 233
Function Generator	33622A	33611A 33612A 33621A 33250A 33120A Opt 001
Digital Multimeter	3458A Opt 002	34470A

Select any option of PXA spectrum analyzer (503, 508, 513, 526, 543, 544, 550) that has a maximum frequency greater than or equal to the maximum frequency of the unit under test.
Select any model of PSA spectrum analyzer (E4440A, E4443A, E4445A, E4446A, E4447A, E4448A) that has a maximum frequency greater than or equal to the maximum frequency of the unit under test.

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.