In 1967 Veselago stated that a medium with negative real parts of the electric permittivity and magnetic permeability would have a negative real index of refraction [1]. In such a medium the electric field, the magnetic field, and the propagation vector form a left-handed (LH) triplet. Because of this relationship, these media have been named left-handed media (LHM). The first negative index medium was developed three decades later when Smith combined an array of split ring resonators (SRRs) and strip wires (SWs) [2]. Typically, in such a medium, in order to determine whether the given structure has a negative index of refraction or not, the transmission through the structure is measured and if a transmission peak is observed in the region where both the real parts of the permittivity and permeability are expected to be negative, then the structure is assumed to exhibit LHM behavior [2, 3, 4], However the emergence of a passband and a transmission peak is not sufficient evidence that the structure exhibits left handedness. When the SRR and SW are combined into a single structure their individual field patterns can interfere in such a way that the LHM behavior is weakened or even lost, whereas still a passband and a transmission peak can be observed. In these situations, in order to correctly predict the left or right handedness, one must rely on other "diagnostic tools" such as calculating or measuring the insertion phase and/or dispersion diagrams.
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