Abstract
A novel frequency-independent printed quadrifilar helix antenna with wideband performance is presented in this paper. The proposed antenna utilizes four simple gradient microstrip lines as radiators, which are wrapped around a thin cylindrical dielectric substrate. Each microstrip line has etched two slots. The introduction of the slots results in a reduced frequency interval between two resonances, making the proposed antenna achieve a wideband characteristic. In addition, the input impedance of the proposed antenna is extracted for parametric analysis. The change rule of the real and imaginary parts of the input impedance indicates that the position of the slot at below (top) could control the lower (upper) resonance point independently. A prototype is simulated, fabricated, and measured for demonstration. The measured impedance bandwidth of the proposed antenna is 42.6% from 1.09 to 1.68 GHz. Moreover, a feeding network adopting a chip balun and two chip hybrid couplers is designed to measure the radiation pattern and axial ratio of the proposed antenna. Finally, the wideband, frequency-independent, wide half-power beamwidth, and excellent circularly-polarized characteristics make the proposed antenna become a competitive candidate in the satellite communication and navigation and positioning systems.
