Metamaterial Aperture for Frequency-diverse Dual-mode OAM Beams

In this paper, a metamaterial aperture for generating electromagnetic vortex waves with frequency-diverse dual-mode orbital angular momentum (OAM) in the X-band (8 GHz{12 GHz) is designed. The electromagnetic vortex wave carrying OAM is also called the OAM beam. OAM beams with different modes can be generated by the proposed metamaterial aperture at different working frequencies Firstly, three kinds of metamaterial units including the rectangular patch unit, the jerusalem cross unit and the swastika unit are designed, respectively. Through optimization, the transmission phase of the unit group can cover 2 pi, which meets the requirements of generating OAM beams Secondly, the metamaterial aperture is divided into two annular regions and metamaterial units with certain transmission phases at corresponding frequencies are distributed at specific annular regions according to the phase distributions of OAM beams. In addition, the design method can be extended to generate frequency-diverse multi-mode OAM beams, which can be used to improve the resolution of radar imaging system. Finally, the metamaterial aperture is modeled and simulated in the Computer Simulation Technology (CST) software. 1-mode and 2-mode OAM beams are generated by the proposed metamaterial aperture at 8 GHz and 12 GHz respectively, which validates its feasibility of generating frequency-diverse dual-mode OAM beams.