Guided-Wave Suppression in Uniaxial Anisotropic Metamaterial Slab for Radiation Pattern Control of Covered Dipoles

A dipole positioned in parallel close to a dielectric cover excites strong guided waves, typically distorting its radiation patterns. This study presents conditions for suppressing guided waves in a uniaxial anisotropic slab and then proposes a uniaxial anisotropic meta-cover to improve the un-roundness of distorted radiation patterns of off-center positioned dipoles. The proposed metamaterial cover (meta-cover in short) of periodic metal mesh unit cells exhibits uniaxial anisotropic properties with electric Drude-model dispersion, suitable for wideband guided-wave suppression. For comparison, the proposed meta-cover and conventional homogeneous dielectric are designed and used to closely cover off-center omnidirectional horizontally polarized four-dipole rings (FDRs). The study theoretically and experimentally verifies that by suppressing the guided waves in the meta-cover, the FDRs achieve an improvement in the un-roundness of the radiation pattern from 17.6 to 5.2 dB over the frequency range from 5.0 to 6.0 GHz, so that coverage efficiency increases from 42.4% to 84.7%. The derived conditions to suppress the guided waves in a meta-cover benefit mitigating cover influences on the radiation performance of antennas in modern wireless systems.