An Empirical Expression to Predict the Resonant Frequencies of Archimedean Spirals

This paper presents an empirical formula to accurately determine the frequencies of the fundamental and higher order resonances of an Archimedean spiral in a uniform dielectric medium in the absence of a ground plane. The formula is based on method-of-moments simulations, which have been experimentally validated. This empirical formula is widely applicable to a broad range of spirals from thin-ring to disk-shaped (ratio of inner to outer radii 0 to 1), with ten or more turns.