A method for the transformation of arbitrary electromagnetic fields based on Huygens principle

The transformation of arbitrary electromagnetic fields is investigated, in order to characterize the near field of the source and transform the result to any location outside the source region. The method presented, referred to as the Huygens principle method, is based on principles of diffraction theory. It is developed from the homogeneous scalar wave equation, and a comparison is made with vector wave equation results based on the Kottler-Franz formulas. The aim is to characterize the sources from measurements made on a surface so as to allow transformation to other locations. The power spectral density is used as the most meaningful characteristic. The method requires measurement of the cross spectral density of the electric or magnetic field. The sensitivity of the Huygens principle method to location error is investigated, and a computer simulation example is presented to illustrate the method. Suggestions for the physical implementation of this transformation method are made