In this paper, we present a metamaterial-based beam splitter. Such a power splitter was made up of a metamaterial sandwiched by two metallic plates. The metamaterial consists of three-dimensional (3D) fishnet arranged in a two-dimensional square lattice. As is well known from Snell's law, the refracted wave tends to be normal to the interface when the wave is incident from a medium having effective refractive index much smaller than unity into the air region. We properly synthesize the metamaterial having effective refractive index smaller than unity. Furthermore, a line source made by a monopole was embedded in the metamaterial to excite four beams propagating toward four directions. In addition to the calculation of wave-propagating characteristics in the metamaterial, we also implemented a beam-splitting structure invoking the unique characteristic of the metamaterial. The electric-field radiating pattern was measured to prove its spatially beam-splitting characteristics. Metamaterial is an artificially engineered structure which obtains its properties from its structure rather than directly from its composition. Generally, a metamaterial is synthesized by embedding specific inclusions, for example, periodic structures, in a host medium. The applications of metamaterial in waveguides and antennas designed were intensively developed [1,2]. A metamaterial with zero-index was demonstrated to have the capability to narrow the far-field pattern associated with an antenna located within it. Besides, a matched zero-index slab could be used to transform curved wave fronts into planar ones [3]. The metamaterial made up of wire medium has been studied intensively, particularly on its effective refractive index, permittivity and permeability. Specifically, the structure composed of metallic mesh wires, which has very small electrical length in the period and wire thickness, can be characterized as a homogeneous medium with a low plasma frequency [4].
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