AngleSensor:

--------------------------------------------------------------------------
   Angle sensor.

   The inputs are the one dimensional state vector [x;v] and a 
   data structure with the baseline and noise. The sensor tracks the
   target.

   Since version 11.
--------------------------------------------------------------------------
   Form:
   theta = AngleSensor( x, d )
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   x       (2,1)   [x;v]
   d       (1,1)   Data structure
                   .b       (1,1)   Baseline
                   .noise   (1,1)   Angle noise (rad)

   -------
   Outputs
   -------
   theta   (1,1)   Angle measurement 

--------------------------------------------------------------------------