Design of a Compact and Wideband Quadrifilar Helix Antenna

Abstract

A compact and wideband quadrifilar helix antenna is presented in the paper. The quadrifilar helix line is printed on the surface of a cylinder substrate with high dielectric permittivity. There are four ports at the bottom of the antenna, and a microstrip line feeding network is adopted combining the four ports to one final port. The antenna is designed, simulated and optimized. 20% with VSWR $< 1.5$ bandwidth can be achieved according to the simulated results. The proposed antenna has very broad beams. In the half-space above ground plane, the minimal gain is -5dB and the maximal axis ratio is 4dB. If the system need an antenna with properties of wide bandwidth, compact size, circular polarization and very broad beam, this antenna should be a good candidate.