-------------------------------------------------------------------------------
   Doppler shift
-------------------------------------------------------------------------------
   Form:
   [fD, fR] = DopplerShift( fT, vR )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   fT           (1,1)   Transmit Frequency (GHz)
   vR           (1,:)   Relative velocity (m/sec)
   
                        
   -------
   Outputs
   -------
   fD           (1,:)   Doppler shift
   fR           (1,:)   Receive frequency (GHz)
                         
-------------------------------------------------------------------------------
   References:	Edde, B., Radar: Principles, Technology, Applications,
               Prentice-Hall PTR, 1995, p. 305.
-------------------------------------------------------------------------------