A low-profile unidirectional antenna enabled by interdigital capacitor loaded metasurface

In this paper, a compact footprint and low-profile metasurface-enabled unidirectional antenna that operates from 4.11GHz to 4.26GHz with a center frequency at 4.2GHz is presented. The miniaturized metasurface, which has a reflection phase of -150 degree at 4.2GHz, was made possible by interdigital capacitor loading, resulting in a unit cell with an electrical dimension of only 0.02λ₀². A finite-sized metasurface with two by three elements was integrated with a planar microstrip fed monopole antenna, enabling a total antenna footprint of around 0.13λ₀² and a thickness of 0.05λ₀. Full-wave simulations show that, even with such a small footprint, the antenna achieves a large front-to-back ratio and a high gain within the targeted operational frequency band.