Low-Profile Mixed-Mode OAM Antenna Based on Impedance-Modulated Surface

A low-profile mixed-mode orbital angular momentum(OAM) antenna based on impedance modulated surface is proposed, which consists of a monopole and a tensor holographic metasurface. This design adopts a partitioning method, where the holographic metasurface is divided into four ring areas. OAM modes of 1, 2, 3, and 4 are generated by these four regions from inside out respectively, and thus realize a directional vortex beam. Besides, the realized directional beam still retains vortex phase distribution, which means this antenna can be employed to improve OAM transmission distance.