Design of six-mode RF-switch reconfigurable quadrifilar helix antenna with stable circular polarization

This paper proposes a pattern-reconfigurable circularly polarized (CP) antenna based on quadrifilar helix antenna (QHA), presenting a compact QHA that generates six reconfigurable CP radiation patterns through two phase-modulated bifilar helices and a balun feeding network with four RF switches. By dynamically controlling the states of RF switches to excite bifilar helices with simple in-phase or reverse-phase signal combinations, the integrated switch-balun system enables real-time pattern reconfiguration among six distinct CP radiation modes. This approach avoids complex structural modifications, enabling seamless switching between horizontal omnidirectional and front-focused modes with stable circular polarization. The measured results show a 12.6% impedance bandwidth (2.23–2.53 GHz) and a 5.3% axial ratio bandwidth (2.37–2.5 GHz), while radiation patterns align well with simulations. Validated through prototype measurements, this RF-switch-driven design simplifies multi-pattern reconfiguration and provides an efficient solution for adaptive wireless systems requiring multi-directional coverage, particularly in UAV-borne communications and low-earth-orbit satellite terminals.