AM Audio Path Offset Calibration

(E8257D, E8267D, E8663D with Option UNT and E8257N Only)

This adjustment calibrates the amplitude modulation (AM) path to remove any offset when AM mode is enabled.

During this adjustment, the AM offsets are separated from the ALC offsets in both linear and exponential mode. A path is selected, the ABUS is zeroed, the ALC LVL_DAC value is recorded using a multimeter connected to Sweep Out, and a power measurement is performed using a power meter connected to the RF output. AM is turned on, the AM_OFFSET_DAC set to 0, and the AM_ABUS value is read and recorded. The AM_OFFSET_DAC is set to 500 and the AM_ABUS read. Using the results of the AM_ABUS reading with the AM_OFFSET_DAC at 0 and 500, a value is calculated and stored so that the AM_ABUS equals 0 V.

Then another power reading is made with AM on. The AM on and off power levels are used to calculate a value for the LVL_DAC so there is < 0.002 dBm difference between AM on and off.

Next, the AM offsets associated with the A11 Pulse/Analog Modulation Generator are eliminated. The routine is performed once for each of the AM modes: INT1, INT2 (not calibrated for the standard E8257N), EXT1 AC, EXT1 DC, EXT2 AC, and EXT2 DC. The instrument is placed in linear mode. With AM off, a power measurement is made, and AM is turned on. The AM_OFFSET_DAC is set to 0 and the AM_ABUS read. The AM_OFFSET_DAC is set to 500 and the AM_ABUS read. The ABUS readings are used to calculate a SCALE_DAC value that is used with the AM_OFFSET_DAC which is used to eliminate AM path offsets. The SCALE_DAC value is stored and the power level difference between AM on and off is checked for < 0.01 dB difference.

Test Equipment

Preferred Model

Alternate Model(s)

Power Meter

N1914A1

E4419B
E4419A

Power Sensor
Only for Opt 520 and 1ED

E9304A Opt H19

E9304A
E9304A H18

Power Sensor
Not required for Opt 520 and 1ED

N8487A

8487A Opt H842
N8485A
N8485A CFT
8485A Opt H842
E9300A Opt H25

Digital Voltmeter

3458A Opt 002

 
  1. 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 Service Note
  2. Option H84 provides reflection coefficient data.

 

Connections and Setup Procedures

  • All test equipment requires a 30 minute warmup period to ensure accurate performance.

  • In the following test setup, cables are designated as solid lines and direct connections are designated as dashed lines.

  1. Connect all test equipment as shown.

  2. Connect GPIB cables to all GPIB-controlled test equipment.

  3. While performing this adjustment, follow all instructions on the controller display.

 

Setup for Power Meter Calibration

 

Setup for AM Audio Path Offset Calibration

In Case of Difficulty

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

  1. Check the equipment setup (see above). If the setup is incorrect, make the necessary corrections and rerun the adjustment.

  2. 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.

  3. If you cannot correct the problem using the troubleshooting procedures in the Service Guide, obtain service from Keysight Technologies. Refer to Contacting Keysight Technologies.