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.