Extreme Aperture Antennas: Radiating and Electrical Performance Enhanced by Metamaterials

In this contribution, we present the design of metamaterials-based flat lens and metamaterial-inspired particles, which have been successfully used to enhance the performance or to add new functionalities to aperture horn antennas. The metamaterial-based flat lens is designed to restore the gain performance of shortened optimum horn antennas. The lens consists of a proper combination of conventional epsilon-positive and epsilon-near-zero materials, in order to achieve the optimum field distribution on the aperture for maximizing the gain over a broad frequency range. The metamaterial-inspired particles are designed for integration directly inside horn antennas in order to provide additional functionalities or simple signal conditioning ability to the radiating element. Among them, filtering operations with a pass-band or a notched-band behavior, combination and splitting capabilities of signals with different carrier or polarization states, polarization conversion properties, and magnet-less non-reciprocity by exploiting spatiotemporal modulation of the particle have been verified both numerically and experimentally.