Twisted waves: Concept and limitations

In this paper we will be discussing the “twisted wave” concept that is based on the idea that the modes of an antenna can be individually modulated, transmitted and detected in the antenna far field. We review twisted wave theory which requires the long distance preservation of a non-uniform phase front resulting in discrete orbital angular momenta associated with each of the antenna modes. We then describe three arguments against the twisted wave concept based on classical electromagnetic theory, the similarity to well known multiple-in-multiple-out (MIMO) methods, and as an apparent violation of the second law of thermodynamics.