A Novel Modified Archimedean Polygonal Spiral Antenna

In this paper, we present a novel 2-18 GHz modified Archimedean polygonal spiral antenna that approximates a circular spiral in its highest frequencies and gradually transforms itself into a square spiral antenna at its lowest frequencies of operation. The design has successfully addressed the problem of high axial ratios associated with ultra-wideband (UWB) rectangular spiral antenna systems. A low-profile, cavity backed polygonal model and two variations of the original design are presented in this study. Our results demonstrate that the polygonal spiral antenna demonstrates excellent axial ratio and gain-bandwidth performance with ≤ 3 dB axial ratio over 97.5% of its operational bandwidth.