One of the critical requirements for proper calibration of Tx power levels (and
of the Rx "magic gain" to a lesser degree) is that the insertion loss of the
cabling setup between your CMU200 and your DUTs (Calypso GSM devices to be
calibrated) needs to be precisely known and accounted for.  Actually measuring
the insertion loss of your cables at the center frequency of each GSM uplink and
downlink frequency band with 0.1 dB accuracy is your responsibility; the rest
of this article will merely tell you how to feed these cable loss numbers to
FreeCalypso RF calibration tools.

In our architecture the software component that takes care of adjusting the
power levels for the cable loss is fc-cmu200d; our fc-cmu200d reads the cable
loss numbers from a configuration file and instructs the CMU200 itself to
perform the actual adjustments.  Furthermore, our architecture allows for
multiple cable configurations.  Some Calypso GSM devices have SMA RF connectors
for attaching the antenna, in which case the calibration coax needs to terminate
in an SMA, others have MS-147 or Murata SWD/SWF RF test ports, in which case the
calibration coax needs to terminate in an MS-147 or Murata probe connector.  If
you are working with different types of Calypso GSM devices, you will need to
switch between the corresponding cable setups, as the cable loss numbers will be
different for each setup: even if you keep the same "main" coax going from your
CMU200 to an SMA and add/remove Murata's SMA-to-SWD/SWF adapter at the end, the
addition or removal of that extra adapter will change the total insertion loss
along the full path, and this change needs to be accounted for.

Cable configuration files are kept in the /opt/freecalypso/rfcal/cableconf
directory; it is up to you how you name your cable configs, but the following
convention is suggested:

* If you have a cable setup that terminates in an SMA connector for calibrating
  Calypso GSM devices with SMA antenna interfaces, the corresponding cable
  config file should be named "sma".

* If you have a cable setup that terminates in an MS-147 probe connector for
  recalibrating Mot C1xx phones or similar, the corresponding cable config file
  should be named "ms147".

* If you have a cable setup that terminates in a Murata SWD/SWF probe for
  working with devices like Openmoko GTA0x, the corresponding cable config file
  should be named "murata".

See cableconf-example for an example of the syntax, but please remember that
you are still responsible for putting in YOUR OWN numbers for the actual
insertion loss of your cable setups.

When you actually run fc-cmu200d to begin a calibration session (see the
General-flow article), you will select the cable configuration to be used
by name with the -c option to fc-cmu200d.