Performance Enhancement of End-fire Bow-tie Antenna by Using Zero Index Metamaterial

In this paper, an epsilon near zero metamaterial (ENZ) structure is proposed for the gain enhancement of a bow-tie antenna which normally has relatively low gain. The proposed antenna consists of a pair of bow-tie radiators, etched on the opposite sides of the dielectric substrate. The single bow-tie antenna loaded with an array of zero-index metamaterial (ZIM) unit cells in the E-plane, whose purpose is to effectively confine the electromagnetic waves in the end-fire direction to enhance the performance of the gain. The proposed structure is fabricated on the same substrate which is used to study the ENZ cell, which is Rogers 6035 dielectric substrate with relative permittivity of 3.5, thickness of 0.508mm and loss tangent of 0.0013. The feeding line to the Bow-tie structure has lambda/4 transformer to provide a good impedance match over the desired frequency band of 34 GHz-40 GHz. The fabricated bow-tie antenna loaded with the proposed ENZ cells exhibits a gain of 8-9.5 dB in the frequency band of 34-40 GHz for fifth generation (5G) cellular communication systems. The simulations are carried out using finite element method (FEM)-based Ansys high-frequency structure simulator (HFSS) and Computer Simulation Technology (CST) Microwave studio. The simulations and measured results have good agreement and the gain enhancement of the ENZ cells is confirmed.