Omnidirectional broadband patch antenna with horizontal gain enhanced by epsilon-negative metamaterial superstrate

It is hard to improve the horizontal gain of broadband omnidirectional patch antenna based on zero-order resonance. Enlightened by metamaterial employed to enhance the directional patch antenna, we devised an epsilon-negative (ENG) metamaterial as a cover that placed above omnidirectional antenna to enhance the horizontal gain. Then, the air layer is replaced by a low permittivity foam for practical application. Measured results prove that this method can improve the horizontal gain more than 30% (0.6 dBi) at various frequencies with roundness below 3 dB. This method provides a novel approach to improve the horizontal gain of broadband omnidirectional patch antenna, which is especially suitable for dedicated short-range communication field.