Generation of Mode-Reconfigurable and Frequency-Adjustable OAM Beams Using Dynamic Reflective Metasurface

Recently, much attention has been paid to beams carrying orbital angular momentum (OAM) for radio communication, which faces a great challenge of dynamic generation of OAM with different topological charges. In this paper, a novel reflective metasurface is designed to generate mode-reconfigurable OAM beams in radio frequency domain. Each unit cell of the proposed metasurface consists of an octagonal ring slot and a varactor diode. The response of each element to incident radio field can be engineered individually by controlling the voltage of the corresponding varactor diode, thereby dynamically producing OAM with different modes. Full-wave simulations show that the designed reflective metasurface can generate frequency-adjustable OAM beams with different topological charges of $l = +1$ , +2, −1, −2 over a frequency range of 5.2 GHz~5.8 GHz. An OAM purity analysis further verified the reliability of OAM beams generated by the proposed metasurface. The obtained results are in good agreements with the theoretical analyses, demonstrating a good prospect of practical application.