Electromagnetic Composite Materials and Metamaterials

In this article, we take an initial look at random composite artificial electromagnetic materials made from mixtures of various elements that have constituent parameters of permittivity and permeability , which can be positive or negative, depending on their composition. Since the invention of radio in the early 20th century, and especially since the invention of radar in the 1930s, these materials have been increasingly used for their electromagnetic properties, and their ease of manufacture and processing. Various methods of simulating these structures make it possible to predict their electromagnetic properties. We will also see that these properties depend not only on their composition, but also on the geometry and electromagnetic properties of the inclusions, as well as their density.

We then turn to periodic composite materials, in particular metamaterials and photonic crystals. This second concept, derived from natural crystalline structures, concerns the realization of periodic materials made up of patterns of different kinds (dielectric, conductive or metallic), making it possible to define and realize artificial materials, whether passive or active, with remarkable properties that do not exist in nature. Simulation methods are totally different in this case, involving the direct resolution of Maxwell's equations.

In this section, we first look at two-dimensional structures such as frequency-selective surfaces, high-impedance surfaces and metasurfaces. For these structures, we no longer speak of permittivity or permeability, but rather of surface impedance and reflection and transmission coefficients, as they behave like interfaces with special properties between media that can be very different. We then turn to three-dimensional periodic structures.

In conclusion, we look at the main areas of application for these materials.

At the end of the article, readers will find a glossary and a table of symbols used.

This article is one of several on composite materials in electromagnetics:

• [E 1 164] Composite materials in electromagnetics – Fundamentals ;