Abstract-A novel broadband horizontally polarized (HP) omnidirectional planar antenna is developed for mobile communications. The proposed antenna consists of four printed arc dipoles that form a circular loop for HP omnidirectional radiation. A broadband feeding network which includes four broadband baluns and an impedance matching circuit is designed to excite the four arc dipoles. An eight-element linear antenna array is developed for 2G/3G base stations. A broadband power divider is used to feed the antenna array. Experimental results show that the HP omnidirectional antenna element has a bandwidth of 31% (1.66-2.27 GHz) while its array has a bandwidth of 34% (1.67-2.35 GHz) and an omnidirectional antenna gain of ∼ 8 dBi. Both of the antenna element and its array have good omnidirectivity over the 10-dB return loss bandwidth. Simulated and measured results for the antenna element and its array are presented.