Normal-Mode Circularly Polarized Helix Antenna and Its Application to End-Fire Array

This paper first introduces two types of novel normal-mode helix elements that can achieve very good omnidirectional circularly polarized (CP) radiation, high radiation efficiency, and compact size. Specifically, one is a hybrid helix structure, and the other is a counter-wound helix structure. Then, the two helix elements are extended for Yagi array and log-periodic array configurations, respectively, for achieving CP end-fire radiation. The demonstration of this work shows that the proposed helices effectively overcome the limitation of the traditional normal-mode CP helix that suffers from extremely low radiation resistance, and they are very promising for realizing compact and wideband CP end-fire array.