Quad-mode radial uniform circular array antenna for OAM multiplexing

This study presents a novel radial uniform circular array (UCA) antenna for quad-mode orbital angular momentum (OAM) multiplexing in the 5.2 GHz band. The antenna can simultaneously generate four OAM modes (±1, ±2) using two radial UCAs printed concentrically on a single substrate. Each UCA is connected to an individual dual-mode feeding network, and generates a pair of complementary OAM modes. The feeding network for each UCA consists of one quadrature hybrid coupler and two circular feedlines, and they can be integrated onto a single substrate. The measured radiation patterns and helical phase wavefronts show the successful generation of four OAM modes by the proposed antenna. The quad-mode OAM transmission test was performed using two prototypes of the proposed antenna, and good isolations >13.7 dB were obtained between four OAM mode channels, which demonstrates that the antenna can be successfully used for OAM multiplexing.