DBBC2 calibration

Calibration Procedure

1) Inject a broad band noise signal into  all of the DBBC boards (e.g. use a splitter)

2) Start the DBBC control software (PFB or DDC), confirm re-programing of the FPGA and wait until programming of the boards is finished

3) Adjust the IF power levels to around 10000

• PFB and DDC mode

In the DBBC2 client manually set the attenuation (e.g. 40) until you reach a target of 10000 counts.

dbbcifa=1,40,1

Check the counts with:

dbbcifa

Alternatively you can let the AGC adjust the attenuation and set it to manual when the correct level is reached.

dbbcifa=1,agc,1,10000

Check the counts with:

dbbcifa

Once 10000 counts are reached just command

dbbcifa=1,man,1

Check again with :

dbbcifa

Change attenuation and repeat until the target has been reached. Repeat for all boards.

• DDC mode only

In addition for the DDC mode the AGC of the BBCs have to be turned of as well with:

dbbcgain=all,20,20

Typical BBC level is a few hundred counts. Check for some BBCs, e.g.

dbbc01
Reply: dbbc01/ 598.0,a,16,1,man,20,20,385,418,0,0
dbbc05
Reply: dbbc05/ 598.0,b,16,1,man,20,20,354,387,0,0

4) start the calibration

•  PFB mode:

calibration

• DDC mode:

calibration=all

5) Update the configuration file

A file containing the results is produced in c:\ (e.g. DATE-calib.txt) by the calibration command. Inspect or plot the DATE-calib.txt file and search for the minimum between the two peaks.Insert the minimum values into the configuration file e.g. c:\DBBC_CONF\dbbc_config_file_104.txt (file name varies depending on the version). Edit the line just above CAT2 entry.

An example of for a calibration plot is shown below, as well as the script to produce such plots. Usage:

calibration_plot.py BOARD_ALL-2019-009T160419-calib.txt

to zoom into a specific region additional limits for x and y can be given: e.g.

calibration_plot.py BOARD_ALL-2019-009T160419-calib.txt xlim=50,150 ylim=2000,5000