Broadband omnidirectional patch antenna with horizontal gain enhanced by near-zeroindex metamaterial cover

Enhancing the horizontal gain of the omnidirectional patch antenna is always a problem with great difficulty. Inspired by near-zero-index metamaterial (NZIM) cover that can improve the vertical gain of a directional patch antenna, the authors designed two kinds of NZIMs that are placed above the broadband omnidirectional antenna to enhance the horizontal gain. Simulated and measured results indicate that both covers can increase the values of horizontal gain >50% (1 dBi) at various frequencies in all directions, which provides a new approach to improve the horizontal gain of the broadband omnidirectional patch antenna.