Axial-Mode Performance Characteristics of a Thin-Wire Square Helical Antenna

Abstract

This paper, using an adaptation of a method described by Kornhauser for a circular helix antenna in a 1951 publication, rigorously develops hitherto unavailable explicit analytical expressions for the far-zone electric fields radiated in free space, by a thin-wire helical antenna, of square cross-section. It is shown in the presentation that these radiation field expressions for the square helical antenna represent a general case, from which corresponding expressions, exactly as published elsewhere for the square-loop and linear geometries, are recoverable: to support the correctness of the formulation. And subsequently using the expressions as basis, the presentation undertakes a systematic investigation of the characteristic performance features of the square helical antenna, mounted on a ground plane of infinite extent; when operated in the axial mode, and for various values of square-loop perimeter and number of helix turns. For computational data, the antenna’s current distribution is determined via the method of moments with piece-wise linear basis and testing functions, after invoking the image theory. In addition to the radiated electric field, numerical results concerning axial ratio as well as the directive gain, for the square helix antenna, and for a range of antenna physical dimensions, are presented in graphical formats. These results very clearly indicate that the axial-mode performance of the square helical antenna is comparable with that of the conventional circular helical antenna.