A Miniature Quadrifilar Helix Antenna for Global Positioning Satellite Reception

The design is described of a very compact quadrifilar helix antenna. A hollow ceramic rod is used as a dielectric load to reduce antenna size, which is only 2.7% of an air-loaded quadrifilar helix antenna. A simple equivalent circuit is established for the proposed quadrifilar helix antenna to demonstrate impedance characteristics. A self-phasing method for achieving circular polarization is also proposed. This method is convenient for tuning circular polarization. Additionally, a compact matching structure is designed to match the proposed antenna, which only utilizes short transmission-line sections and one capacitor. For experiments, the proposed antenna is designed at 1.575 GHz such that it can be utilized for global position system. Measurement and simulation results agree. A hemispherical pattern with a beamwidth of 150^deg is measured. This circular-polarized pattern with a wide beamwidth is feasible for mobile applications.