Planar dual-band omni-directional UHF antennas employing a composite right/left-handed double-sided metal layer structure

This article presents planar dual-band omni-directional antennas employing a composite right/left-handed (CRLH) metamaterial for UHF applications. The antennas are compact and in a simple double-sided planar configuration without using vias or lumped-elements and have an omni-directional radiation pattern regardless of having a ground plane at the backside. A dual-band antenna operating at a pair of the negative (f_-1) and positive (f₊₁) resonant frequencies is designed at 373/817 MHz and the dual-band operation with omni-directional radiation patterns are demonstrated. The physical size of the presented antenna is lambda_-1/13 times lambda_-1/18 times lambda_-1/1005 at f_-1, and lambda₊₁/8 times lambda₊₁/6 times lambda₊₁/459 at f₊₁, where lambda_-1 and lambda₊₁ are free space wavelengths at f_-1 and f₊₁, respectively. Maximum measured gains at f_-1 and f₊₁ are -13.8 dBi and -0.5 dBi, respectively.