Miniaturization of helical antennas using dielectric loading

A method for the miniaturization of the well-known monofilar axial-mode helical antenna is presented. The height (and other dimensions) of the antenna is reduced by loading it with a dielectric hemisphere of high permittivity and addressing, in an intelligent manner, two accompanying impedance mismatches that are introduced. Simulations show that a 46.8% reduction in the total height of the antenna is achieved while maintaining the wide input impedance bandwidth (i.e., 48.0%), the gain pattern stability over frequency, and the required axial ratio for circular polarization over the entire passband. All of these characteristics were achieved while maintaining essentially the same lowest frequency of operation as the unminiaturized version of the antenna.