The properties of artificial dielectrics comprising arrays of conducting elements

Part 1 of the paper describes a theoretical analysis of the effective permittivity of arrays of perfectly conducting elements of simple geometric shapes¿e.g. cylindrical rods, thin strips, spheres and discs¿ and the results of a supporting experimental investigation on arrays of metallic elements of these shapes at a frequency of 1 000 c/s. Dielectric media of this type are being used for the construction of centimetre-wave lenses. It is shown that representation of the elements as simple dipoles is inadequate at high concentrations and that account must then be taken of higher-order multi-pole interaction between them. Where evaluation of the latter has proved practicable, the experimental and theoretical permittivity values are found to be in close agreement over the whole range of concentration investigated. Part 2 describes an experimental investigation of the permittivity and dielectric-loss characteristics over the frequency range 400¿10 000 c/s of a cubical array of spherical elements composed of imperfectly conducting material as a function of the concentration of these elements, and discusses the results in terms of the theoretical analysis given in Part 1. This investigation is an extension of earlier studies of the behaviour of composite dielectric materials.