Applicability of Mode Division in Far Field Radiation of Orbital Angular Momentum Electromagnetic Waves

Electromagnetic waves with orbital angular momentum (OAM) with different are found to be orthogonal in quasi near field region. This property makes OAM to be useful for mode division and multiplexing. In this paper, the orthogonality property of OAM is studied in the far field. A simple analytical formulation based on a circular array of arbitrary oriented infinitesimal dipoles is used to model the source and the receiver of OAM waves. This model is used to study the received signal radiation pattern between different configurations of OAM sources and receivers. This study shows the applicability of using OAM mode division in far field. The received signal radiation patterns between similar configurations of OAM sources and receivers are also investigated. This study shows the applicability of OAM modes to be used for spatial division and multiplexing too.