Microwave modes of ambidextrous helices

This work presents an investigation into the electromagnetic properties of ambidextrous helices, structures composed of equal numbers of left- and right-handed turns, operating in the gigahertz frequency range. Unlike conventional single-handed helices, which support only hybridized, elliptically polarized modes, ambidextrous helices exhibit two distinct linearly polarised resonant modes: one with electric dipole-like behaviour and the other with magnetic dipole-like behaviour. Using a combination of numerical simulations and experimental validation, we analyse the two lowest-order modes of a four-turn ambihelix, highlighting their unique characteristics. A key result of this study is the demonstration that these resonances can be independently tuned through geometric modifications. By adjusting the pitch, the frequencies of the electric and magnetic dipole modes can be exchanged in frequency order and indeed made to be coincident. These findings underscore the ambihelix's potential for reconfigurable and multifunctional microwave devices. Its dual-mode capability, combined with geometric control over resonance order and frequency, offers new design flexibility for compact antennas, metamaterials, and polarisation-sensitive applications. The four-turn ambihelix studied here represents just one example from a broader design space, highlighting the rich potential of ambidextrous helices for future electromagnetic engineering.