Investigation of an octafilar helix antenna

An octafilar helix antenna for circular polarization (CP) is proposed and investigated theoretically. The moment method is applied to find the rigorous solutions of the current distributions on bifilar, quadrifilar and octafilar helix antennas of different helix lengths. Comparisons of calculated and available experimental results for a quadrifilar helix antenna are presented, indicating good agreement. A cardioid shaped radiation pattern with excellent circular polarization over a wide angle is obtained for the octafilar helix antenna. For a 1/2 turn octafilar helix antenna, the axial ratio is less than 3 dB for θ ranging from -65 to 65 degrees, while the gain varies from 13.7 dB at θ=-65° to 16.5 dB at θ=0°. The radiation characteristics of an octafilar helix antenna on a conducting box are illustrated.