Exploiting intrinsic dispersion of metamaterials for designing broadband aperture antennas: Theory and experimental verification

The intrinsic frequency dispersion has usually been considered as a relevant drawback of metamaterials, limiting their application to narrowband microwave components. However, we have recently demonstrated that a particular metamaterial-based lens, consisting of a combination of an epsilon-near-zero (ENZ) material and air, is able to enhance the gain of short horn antennas over a broad frequency range. This result was achieved by exploiting the dispersive nature of ENZ metamaterials. In this communication, we further discuss the latter aspect, giving more details about the physical mechanism enabling broadband operation of shortened horns loaded with ENZ-air lenses. The discussion is supported by a set of experimental results obtained on a fabricated prototype.