Short-Length and High-Aperture-Efficiency Horn Antenna Using Low-Loss Bulk Anisotropic Metamaterial

An empty horn antenna is filled with a bulk anisotropic metamaterial to enhance its gain and aperture efficiency. Radiation patterns in both the E-plane and the H-plane are improved owing to the anisotropic permittivity and the anisotropic permeability. Aperture efficiency over 70% is achieved despite of its short longitudinal length
$\sim {\lambda _0}$
. Insertion loss below 0.18 dB and energy reflection below
$ - 20~\hbox{dB}$
are obtained, which are quite small compared to most metamaterial-based antennas. The metamaterial-filled horn is fabricated and tested, and the measured results agree very well with the simulated results.