A Circularly Polarized Quadrifilar Helix Antenna With Steerable Beam

This paper presents our study on a circularly polarized (CP) beam steering quadrifilar helix antenna (QHA) for the applications of wireless communication, satellite navigation and wireless power transmission. The proposed antenna is composed of four helical wires with variable feeding phase differences, which is different from a conventional QHA. It is shown to realize one cardioid pattern towards the broadside, and four off-boresight tilted beams over a half space by controlling phases on the helix elements in simulation. A feeding network was developed to excite the broadside and tilted beam modes for proving the concept in experiment. The measured results of the broadside radiation mode are in good agreement with the simulated ones. The impedance bandwidth of the proposed antenna can cover 1.26-1.65 GHz with a 3-dB axial ratio bandwidth of 1.1-1.8 GHz. The gain in the whole working band is higher than 2.1 dBi. And over 70% radiation efficiency can be achieved.