Millimeter-Wave Orbital Angular Momentum Radiations from Photonic-Based Transmitter

A microstrip patch-antenna-based realization of a radiating structure for millimeter-wave orbital angular momentum (OAM) field emissions is presented. The OAM modal fields are synthesized with the structure together with a phasing network comprising a 4 x 4 Butler matrix and bended microstrip sections. It is shown that the demonstrated structure is poised for the simultaneous radiations of orthogonal OAM modes +1 and -1 at W-band, and the simulated radiation efficiency is about 64%. The OAM radiating structure in conjunction with ultra-fast photodiodes could be exploited to realize photonic-based transmitters for multi-channel millimeter-wave over fiber communications at the last mile.