Low-Profile Dual Polarized Multi-Mode OAM Antenna Array

A dual-polarized multi-mode orbital angular momentum (OAM) microstrip antenna array using differential feeding has been proposed in this paper. The antenna element consists of four radiation patches and four driven patches, with two pairs of differential feeding ports. The symmetry of the antenna structure allows the radiation patches to be shared by the adjacent antenna units in the array, which reducing the overall size of the 2×3 array. By controlling the phase of the feeding ports, the array radiates four kinds of the OAM waves, i.e., the OAM modes of $l = +1$ and +2 in $x$ polarization and $l = -1$, and -2 in $y$ polarization. The simulated results show that the antenna has a bandwidth ($\vert S_{dd11}\vert < -10$ dB) of 3.4-3.9 GHz (13.7%), and the resulting array has a cross-polarization ratio of 24 dB. Good OAM wave characteristics obtained by the proposed array verify the feasibility of the integrated design of polarization multiplexing and mode multiplexing.