Circularly Polarized Millimeter-Wave Hemisphere DRA Employing FSS Polarizer and Dielectric Superstrate for 5G Applications

This paper presents a compact, wideband, high-gain, and circularly polarized (CP) hemisphere dielectric resonator antenna (HDRA) designed for 5G applications. The linearly polarized (LP) source antenna includes an HDRA on a ground plane, excited by a 50 Ω microstrip line to enhance radiation efficiency at millimeter-wave (mm-wave) frequencies. Power is coupled to the HDRA through an annular slot in the ground plane. A wide bandwidth from 20 GHz to 28 GHz is achieved by overlapping adjacent excited modes. To convert LP to CP, frequency-selective surface (FSS) superstrate cells are placed at an optimized distance above the HDRA. To improve the 3-dB axial ratio (AR) and gain of the HDRA, a 2×2 HDRA with a sequential phase feeding network and an additional dielectric substrate above four 3×3 FSS subgroups is used. The antenna parameters, such as S11, gain, AR, and radiation patterns, are analyzed, fabricated, and measured. The measured results show an S11 from 20 GHz to 28 GHz (33.33%) with a peak gain of 11.8 dBi and a 3-dB AR from 20.5 GHz to 28 GHz (31%). These results confirm the antenna's suitability for IoT and 5G applications.