Sub-6 GHz Dual-polarized Dual-mode OAM Antenna

In this paper, we present a dual-mode, dual-polarized orbital angular momentum (OAM) antenna, implemented as a fourelement uniform circular array (UCA) with a series-fed network on a single-layer substrate. The novelty of the antenna lies in its ability to generate four orthogonal states simultaneously in a single transmission channel — two from l = ±1 OAM states and two from vertical/horizontal polarizations — without requiring multilayer feeds or complex phase-shifting networks. Full-wave simulations and experimental measurements have been used to validate the antenna’s performance within the 5.85–6.1 GHz band. Far-field radiation patterns exhibit the characteristic vortex-beam profile, featuring a conical shape with a central null, while phase distributions reconstructed via FFT-based holography confirm the generation of distinct OAM modes. The antenna has four feed ports; of these, activating Ports 1 and 4 yields the highest OAM modal purity at 6 and 6.1 GHz, while Ports 2 and 3 peak in purity at 6.1 GHz. Owing to its compact, reconfigurable architecture, the designed and tested antenna is well-suited for integration into space-and power-constrained platforms such as UAVs, IoT devices, and full-duplex MIMO systems.