Low-profile unidirectional microstrip-fed slot antenna using metasurface

A new design for a microstrip-fed slot antenna (MFSA) is proposed and developed for improving bandwidth, gain and reducing back radiation. In contrast with most uni- directional MFSA, a metasurface as a superstrate is employed to reduce the back-lobe radiation and enhance the gain with- out a metal reflector. The metasurface exhibits the near-zero permeability (0<; μ <;1) and negative reflection phase. Design considerations for the proposed structure are given, and the design is validated by measurements. The measured radiation patterns show that the proposed structure can offer a high radiation efficiency, a good front to back radiation ratio, and a high co-cross polarization ratio. Due to the negative reflection phase of metasurface, the overall thickness of the proposed antenna is only 9.9 mm, which corresponds to λ₀/12 at center frequency of 2.45 GHz.