Wideband Omnidirectional Circularly Polarized Antenna for Millimeter-Wave Applications Using Conformal Artificial Anisotropic Polarizer

A wideband omnidirectional circularly polarized (CP) antenna using a conformal artificial anisotropic polarizer is proposed for millimeter-wave applications. The antenna consists of three parts: an omnidirectional linearly polarized (LP) radiator, an annular hyperbolic lens, and a conformal anisotropic polarizer. The annular hyperbolic lens regulates the spherical wavefront from the LP radiator into a cylindrical shape prior to propagating into the conformal artificial anisotropic polarizer. Each curved slab of the polarizer is conformally tilted 45° to the incident electric field. Therefore, the conformal polarizer is the three-dimensionalization of the 2-D planar artificial anisotropic polarizer. The polarizer designing methodology is the first of its kind to generate wideband CP wave omnidirectionally. The hyperbolic lens and the conformal polarizer are fabricated together using stereolithography (SLA) 3-D printing technology. The measurement results show that the antenna has a wide operating bandwidth of 45% (from 24 to 38 GHz), which completely covers potential 5G 28 GHz spectra. The proposed design has a low fabrication complexity and brings possibilities for high-speed wireless communications using circular polarization.