Helix Design for cylindrical helix antennas with matching sections

Abstract

A helix antenna must be designed to meet a performance specification: minimum gain, 3 dB beamwidth between a minimum and a maximum value; maximum axial ratio; and a frequency bandwidth over which these values must be maintained. A design consists of specifying the diameter, the pitch angle and the number of turns. A computer program called Helix Design is presented for developing specific designs for a helix antenna over an infinite ground plane. Assuming that the circumference of the helix is one wavelength in the center of the bandwidth, Helix Design identifies all combinations of pitch and turns that meet the specification. The enhanced version of Helix Design described in this paper lets the user terminate the helix with a tapered “matching section”, and compare the performance of helices without and with the matching section. The Helix Design program can create a movie of the antenna performance as a function of frequency over the specified bandwidth. Helix Design should help engineers to rapidly focus on the pitch and number of turns that can realize a particular specification.