Low-cost square cross section helical antennas

Abstract

Square and other cross section helical antennas have several advantages over the conventional circular cross section helical antennas used in satellite communication and other applications. The linear segments which make up a. square cross section helical antenna can be easily supported on a structure which can be cheaply designed and manufactured even for variable cross section or pitch helical antennas. This structure has the additional advantage of having minimal conductor-dielectric proximity, thus virtually eliminating unwanted frequency shift and loss due to dielectric loading. The linear elements are also well suited to simulation using the method of moments, in which cylindrical conductors are nearly always standard elements. Other polygonal cross sections allow some improvement in the axial ratio performance of the helical antennas. The theory and history of helical antennas is discussed, and axial-mode helical antenna models designed to illustrate the relative performance of circular and square helical antennas are presented. Simulations of these models and others with other cross sections were performed using WIPL, a method-of-moments simulation software package, and these simulation results are discussed. Circular and square helical antennas were constructed and measured, and the effects of dielectric loading immediately within the helical winding measured. These simulation and measurement results illustrate the performance advantages of square and other non-circular cross sections for helical antennas.