Design of horizontally polarized omni-directional antenna by characteristic modes analysis

This paper presents a two-notch antenna cut on a small ground plane excited out of phase to a radiate horizontally polarized omnidirectional pattern. The radiating modes of this antenna is evaluated by characteristic modes analysis to obtain omni-pattern. The second mode provides a loop current in horizontal plane, radiating omni-pattern with small ripples. To improve the uniformity of pattern, this paper also proposes an array with twisted elements in vertical axis.