Generation and Analysis of High-Gain Orbital Angular Momentum Vortex Wave Using Circular Array and Parasitic EBG with oblique incidence

This paper presents an effective method for high-gain orbital angular momentum (OAM) vortex wave generation based on the integration of a circular antenna array (CAA) with a parasitic electromagnetic band gap (EBG) structure, which is referred to as the EP-CAA. The resonant height of the EBG structure at different oblique incidences is analyzed parametrically based on the defect mode transmission mechanism to achieve reasonable predictions of a consistent 3-dB gain bandwidth with optimal gain enhancement for different OAM modes. The effective radiation aperture of the EP-CAA at oblique incidence is proposed for analytical calculation of the aperture efficiency of the OAM beams (OAM-AE). A Wilkinson power divider (W-PD) is designed to extend the operating bandwidth of the EP-CAA, and the proposed W-PD arrangement is applicable for feasible OAM modes. Fabricated prototypes of the EP-CAA carrying four OAM modes operating at 10 GHz are measured to verify the effectiveness of the theoretical analysis, the maximum realized gain for different OAM modes are confirmed to be enhanced by at least 6 dB in 5% 3-dB gain bandwidth. The divergence angles of different OAM modes can be effectively concentrated using the proposed EP-CAA.