An algorithm to compute the radiation center of an antenna, using the Spherical wave expansion (SWE) of the far field or the far field directly, is introduced. The method is based on the angular momentum that is uniquely defined for any antenna far field pattern. The radiation center is defined as the phase reference point where the angular momentum is minimized and corresponds to minimizing the phase variations in the antenna far field pattern. In addition, this approach also allows for determination of the current distribution axis.