Height Reduction of the Axial-Mode Open-Ended Quadrifilar Helical Antenna

This letter addresses the miniaturization of the open-ended quadrifilar helical antenna for satellite VHF frequency band telemetry links systems. The miniaturization is achieved using combinations of sinusoidal profiles, and several designs are obtained using an optimization process based on intensive electromagnetic simulations. The design and experimental validation are reported in this letter, and a significant height reduction from 48% to 72% is obtained using various combinations of sinusoidal profiles (i.e., wires mathematically described by sinusoidal functions) without a significant degradation of the radiation pattern, directivity, and polarization purity. Moreover, the input matching is slightly improved for the compact antennas. It was observed that the efficiency and gain do not decrease linearly with the reduction of the antenna height.