Abstract
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.
Highlights
We present an effective high gain orbital angular momentum (OAM) vortex wave generation approach based on the integration of a circular antenna array (CAA) with an electromagnetic band gap (EBG) superstrate
Simulations and measurements show that the gain enhancement of the CAA when integrated with the EBG superstrate is at least 6 dB for all the OAM modes when compared with the original CAA
Theoretical principles are deduced for the design of the EBG superstrate and determination of the resonant height for maximum gain enhancement with a reliable prediction of 3-dB gain enhancement for different oblique angles of incidence
Summary
Devices because of their curved structures. Recently, W. Characteristics of the electromagnetic band gap (EBG) structure with different oblique incidence angles are analysed systematically using the theory of defect mode transmission[29] to provide a reasonable and convincing design prediction of the high gain achievement and 3-dB gain bandwidth for arbitrary OAM modes. A novel and detailed design process to achieve high gain performance for arbitrary OAM modes characterized by their varied main lobe angles is provided. The proposed high gain OAM generation method offers the significant advantage of a reasonable and convincing high gain OAM prediction and a 3-dB gain bandwidth with concentration of different OAM mode’s main beam lobes, and provides economic advantages including structural simplicity and ease of fabrication based on use of unprinted dielectric slabs with lower permittivity. Since a homogeneous dielectric superstrate is applicable for dual-linearly or circularly polarization due to the structure symmetry, and the proposed design, which is based on unprinted homogeneous dielectric slabs, has potential applications for an extension of a linearly polarized CAA to dual-linearly polarized and circularly polarized CAA with corresponding antenna element serves as the CAA element
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