I. Introduction
Composite structured materials have attracted growing interest in recent years due to their potential applications such as optical waveguides, high-dielectric thin-film capacitors, captive video disk units, and novel antennas [1]–[3]. Recently, a new class of these structured materials metamaterials with simultaneously negative permittivity and permeability has inspired great interests in their unique physical properties [3]–[6]. They have shown great potential in many applications such as super lenses, filters, subwavelength resonant cavities, waveguides, and antennas. It is of particular interest to consider the bianisotropy [7], [8] of the metamaterials, such as the design of complementary split-ring resonators (SRRs) [9] and extraction of bianisotropic constitutive parameters for SRR-based metamaterials from -parameters [10]. It was recently shown that negative refraction can be achieved by materials with positive parameters provided one of the materials is chiral or gyrotropic [11], [12].