All-metamaterial-based subwavelength cavities (λ∕60) for ultrathin directive antennas

Abstract

In this letter, we present the characterization and modeling of a metamaterial-based resonant cavity for ultrathin directive printed antennas. A planar artificial magnetic conductor is used for the two reflectors of the Fabry–Pérot-type resonant cavity. One reflector behaves as a high impedance surface, and serves as a substrate for the printed antenna. The other reflector is a partially reflective surface used as a transmitting window. The cavity is operated on subwavelength modes, the smallest cavity thickness being of the order of $\lambda ∕60$ . A drastic enhancement of the antenna directivity and gain is obtained over a relatively wide band from $7.5\text{to}10.1\mathrm{GHz}$ , corresponding to a range of cavity thicknesses from $\sim \lambda ∕3$ to $\sim \lambda ∕60$ . The cavity resonance is seen to be correctly predicted from the standard ray theory approach.