Triple-feed circularly polarized triangular slot antenna using metamaterial transmission lines

This article presents a metamaterial transmission-line-based triple-feed network, which is meant for wideband circularly polarized antennas. The feed network itself is capable of an octave bandwidth, from 1.6 to 3.2 GHz, for an amplitude error of ±0.5 dB and phase error of ±10°. Prototype of a triangular slot antenna was implemented to validate the proposed triple-feed network. The measurement results show that the entire antenna has an impedance bandwidth (standing-wave-ratio ≥ 2) of 73.4%, whereas the 3-dB axial-ratio bandwidth is obtained at 27%. Bidirectional beam patterns with opposed polarization senses have been observed.