Axial ratio enhanced ultra wideband slot spiral on hybrid ebgs

We present a low-profile ultra wideband slot spiral antenna on a hybrid EBG-based reflecting cavity. A unique aspect of the proposed hybrid EBG impedance surfaces is its wide bandwidth performance via constructive interference of the ground plane with the antenna. This characteristic leads to highly improved axial ratio performance as compared to spirals on a metallic ground plane cavity. The proposed hybrid EBGs achieved a 7:1 bandwidth from 0.7GHz to 5GHz with <;4dB axial ratio. Concurrently, the cavity depth of this antenna is only 13mm, and 0.03λ_700MHz at its lowest operational frequency. As such, this slot spiral is attractive in enabling low-profile and conformal antenna installation for body-worn applications.