A compact omni-directional circularly polarized antenna

A compact omni-directional circularly polarized antenna is proposed in this paper. The antenna consists of four bended dipoles and an integrated feeding network simultaneously exciting these four dipoles. Horizontal and vertical polarized field components are generated through the corresponding parts of the bended dipoles, and 90° phase difference between them are naturally guaranteed. With a size of 0.35λ₀×0.35λ₀×0.13λ₀, the antenna exhibits a bandwidth of 9.8% (|S₁₁|≤ -10 dB and AR≤ 3 dB) and a left-handed CP average gain of 0.68 dB in the azimuth plane at the center frequency 2 GHz.