Natural and metamaterial spiral antennas

Abstract

A low-profile cavity-backed spiral antenna with an absorbing strip exhibits wideband radiation characteristics. An EBG reflector is useful in designing a small spiral for medium frequency bandwidth operation. A modified EBG reflector contributes to mitigation of the partial deterioration of the antenna characteristics in a low-profile equiangular spiral antenna. The circularly polarized radiation from a metamaterial spiral is left-handed at one frequency and right-handed at a different frequency.