An investigation into the properties and limits of quasi-taper helical antennas

A simple and reliable technique for designing quasi-tapered axial-mode helical antennas has been formulated which maximises the gain bandwidth to over 2:1. By keeping the ratio of lower-to-upper uniform spiral diameters equal to approximately 1.41 and the axial lengths of the uniform spiral components approximately equal, the gain bandwidth is maximised and there is less than 3 dB of variation in the maximum gain over the working frequency range. It was also found that the larger uniform spiral section essentially governs the antenna, while the smaller spiral simply enhances the high frequency gain.