Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_headmodel_infinite”.

  FT_HEADMODEL_INFINITE returns an infinitely large homogenous
  volume conduction model. For EEG the volume conductor can be used
  to compute the leadfield of electric current dipoles, for MEG it
  can be used for computing the leadfield of magnmetic dipoles.
 
  Use as
    headmodel = ft_headmodel_infinite;
 
  See also FT_PREPARE_VOL_SENS, FT_COMPUTE_LEADFIELD