T2 mode quadrifilar helix antenna fed by coaxial line with omni-directional circular polarization pattern

A novel T2 mode quadrifilar helix antenna (QHA) fed by a coaxial line is introduced in this article. The inner and outer conductors feed directly across to the four arms of QHA, achieving a phase relation of 0-180-0-180. At the same time, the helix arms are narrow in front half part and wider back, and the absorbing conductor lines are loaded at the end of QHA. Experimental results are in good agreement with simulation results. The QHA achieves a gain of 10.5 dBi, an AR of 1.3 dB, and a smoothness of 2.3 dB in azimuth-plane, providing a technical approach of single antenna to realize omnidirectional circular polarization pattern.