Calculation of antenna radiation center using angular momentum

An algorithm to compute the radiation center of an antenna based on the Spherical wave expansion (SWE) is presented. The method is based on the angular momentum vector quantity that is uniquely defined for any antenna far field pattern. The radiation center is defined as the unique point where the magnitude of the angular momentum is minimized with respect to active translations of the far field. This corresponds to minimizing the phase variations in the antenna far field pattern. In addition, the current distribution axis can be determined, corresponding to minimization of the vertical component of angular momentum with respect to rotations.