Toward Metantennas: Metamaterial-Based Antennas for Wireless Communications

Antennas have historically been the most common electromagnetic (EM) technology for wireless communication systems. Antenna as hardware is entirely dependent on the EM properties of the materials used, mostly related to the permittivity and permeability. In addition to natural materials, such as good conductors and low-loss dielectrics, metamaterials (MTMs) have been proposed as artificial structures engineered for unique EM properties that are not found in nature. MTMs have enabled new methods of controlling EM fields and wave propagation, resulting in the rapid development of innovative antennas based on MTMs, otherwise known as metantennas. Metantennas have been mostly developed to address critical challenges by increasing antenna gain and bandwidth while decreasing antenna volume and profile. This article presents three common metantenna designs that demonstrate how the metantenna technology addresses the most critical challenges in antenna design, that is, achieving a wide bandwidth and a high gain, as well as a miniaturized size. These designs include a low-profile wideband metantenna for 5G NR small cells using anisotropic high-permittivity MTM; a wideband antipodal antenna loaded with zero-index MTM for gain enhancement; and compact multiple-beam Luneburg lens antennas using transformation optics methods and MTM implementation. The designs demonstrate the advantages of metantennas over traditional antennas for the fifth and sixth generation communications as well as satellite communications.