Design of a Quadrifilar helical antenna with high phase center stability

A half-wavelength and half turn quadrifilar helical antenna working at 450MHz is designed to provide wide angle, hemispheric coverage with high phase center stability. We apply the space-filling curves´ principle to design a compact and symmetric feeding network with one 180° hybrid and two 90° hybrids, which can provide 90° phase difference among the four arms with uniform amplitude. The simulation results from the CST software illustrate that the antenna´s half-power beamwidth exceeds 110? and the phase center variation is within 1mm at different elevations ranged from -55° to +55° over 20MHz bandwidth, which demonstrate that the proposed antenna design is quite applicable for satellite navigation system.