Antennas and metamaterials

Antennas are key components of telecommunications systems, radar, and the Internet of Things, but their performance in terms of operating frequency band, gain, and size is constrained, particularly by the physical limitations of conventional materials.

Metamaterials emerged in the early 2000s and have since sparked extensive research. These are artificial structures with extraordinary electromagnetic properties, such as a negative refractive index or controlled permittivity and permeability. These properties, which do not exist in nature, offer new degrees of freedom for antenna design. They enable the development of new antenna systems capable of improving radiation, controlling it, and reducing their size.

The study of interactions between antennas and metamaterials represents a dynamic field of research that combines physics, electromagnetism, and telecommunications systems engineering. There is a vast body of work on metamaterials, and it is important to precisely define the terms used in order to navigate this field and better appreciate the scope of potential applications. Once the terminology is understood, the initial studies on negative permittivity and permeability, as reviewed here, will demonstrate how to synthesize these materials under key modeling and homogenization assumptions. Other metamaterials, such as right-handed and left-handed composite lines, high-impedance surfaces, and artificial magnetic conductors, will also be presented, and their essential characteristics—which are necessary for their design—will be detailed. This initial phase is essential for the proper use of metamaterials with antennas.

In many applications, antennas are located in very close proximity to metamaterials and necessarily interact with them. The challenges are varied and thus address the reduction of dimensions in volume or thickness, the increase in directivity or even gain, and beamforming or beam scanning. The goal is therefore to provide the reader with a number of methods for designing the antenna in conjunction with the metamaterial whenever possible, to clarify certain limitations, or simply to highlight the benefits of the proposed metamaterial-based solution.

At the end of the article, the reader will find a glossary of important terms and expressions used in the article, as well as a table of notations and symbols.