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Backward Wave Propagation of a Uniaxial Anisotropic-Negative Slab Composed of Metallic Spirals

1. Introduction It has been theoretically shown that backward waves can be supported not only by double-negative materials with simultaneous negative permittivity and permeability [1] but also by uniaxial anisotropic single-negative slabs with a negative component of permittivity or permeability tensor [2]. The uniaxial anisotropic single-negative materials are potentially advantageous in row loss characteristics as well as a simple configuration because only a single kind of the constituents is required compared with double-negative materials of two kinds of constituents, typically split-ring resonators and wires. Although the backward wave support has already been shown, there is little experimental verification so far, as far as the authors know. In this paper, a uniaxial anisotropic slab with a negative component of the permeability tensor is designed at microwave frequency band by using a two-dimensional (2D) periodic array of metal spirals on a dielectric substrate and backward wave propagation characteristics supported by the structure are experimentally investigated.