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

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 λ ∕ 60 . A drastic enhancement of the antenna directivity and gain is obtained over a relatively wide band from 7.5 to 10.1 GHz , corresponding to a range of cavity thicknesses from ∼ λ ∕ 3 to ∼ λ ∕ 60 . The cavity resonance is seen to be correctly predicted from the standard ray theory approach.