Reducing the size of helical antennas by means of dielectric loading

Helical antennas have long been known as an excellent choice for point to point communications. The lower the desired operational frequency of the antenna, the larger the physical size of the antenna. In order to overcome this issue, the University of Missouri-Columbia´s Center for Physical and Power Electronics has been actively researching the properties of dielectric loaded antennas. Based on simulation models, it has been found that the addition of a dielectric material within the core of a helix will translate into a reduction in the operational frequency of the antenna. Using this knowledge, a 18.6mm diameter × 81mm tall helical antenna was designed around a core with a dielectric constant of ε_r=45. This yielded a 65.4% decrease in the antenna´s operational frequency from 5.13GHz to 1.775GHz as well as a 95.86% decrease in the physical size of a comparable 1.75GHz air core helical antenna. The program CST Microwave Studio was used to simulate these antenna designs derived from Krauss´s formulas. The purpose of this paper is to describe the simulations and design steps that have shown to significantly reduce the physical size and center frequency of an axial mode helical antenna by loading it with a high dielectric core.