Agilent Technologies E4438C - Manual (Page 119)

Adjustments
Burst Modulator Calibration
4- 27
Burst Modulator Calibration
Description
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 properly adjusted, a one-volt signal on the input will result in a
10 dB drop in power level. The calibration involves the adjustment of three DACs (BURST BIAS, BURST
GAIN, and BURST OFFSET) at several different frequencies. The BURST OFFSET DAC sets the initial
current level through the burst modulator diode. The BURST GAIN DAC is used to calibrate the input
voltage level to the burst driver circuit. The BURST BIAS DAC sets the breakpoint at which the modulator
switches from a logarithmic to a linear transfer function. The results are stored in the calibration arrays
associated with each DAC.
Required Test Equipment
• Agilent 8904A function generator (used as audio source)
• Agilent 8563EC Option 001 spectrum analyzer
• Agilent E4400-60073 digital test card
• Agilent 3458A Option 002 digital multimeter
Procedure
Figure 4-20 Burst Modulator 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.