Low Loss Anisotropic Circular Near-Zero Flexible Metasurface for Gain Enhancement

Abstract

This paper proposes a new low loss high dielectric substrate made of CaTiO3 incorporated butyl rubber (CBR). The synthe-sized material has a dielectric loss of 0.0048 and dielectric constant of 11.7. A novel circular anisotropic structure is used in the design of metamaterial unit cell. This metamaterial structure exhibits near-zero refractive index at 2.4 GHz. The extraction of refractive index is done from the scattering parameters using generalised sheet transition condition. An array of 3×3 unit cell is the metasurface superstrate, which is proposed for the gain enhancement. It is kept above the microstrip patch antenna working at 2.4 GHz. The proposed superstrate provides a gain enhancement of 4.6 dB. The height between the antenna and superstrate is optimized to 0.088 λ. The enhancement of gain on metasurface substrate with different loss tangents is analyzed. The simulation and measurement results of antenna with superstrate show good agreement with a peak gain of 7.6 dBi. The radiation efficiency of the antenna is increased by 42%.