A compact metamaterial with multi-band negative-index characteristics

In this article, a compact multi-band negative-index metamaterial (NIM) operating under along the plane incidence has been introduced. Compared to other multi-band NIM based on stacked cell-based approach, the proposed design does not require unit cells of different dimensions to be placed adjacent to each other for realization of a multi-band negative-index of refraction. As a result, the proposed NIM is less influenced by the problem of higher-order Bloch modes. Moreover, the reported NIM is free from anomalies of cross-cell interconnection, which is a typical problem associated with multi-band NIM based on split-ring resonator–wire topology. The proposed NIM has been realized by imprinting a resonantly coupled pair of electric-LC resonators and a hybrid-shaped loop resonator on the opposite sides of a dielectric substrate. The multi-band negative-index of refraction has been confirmed by both simulation and measurement. The investigated structure indicates three bands of negative refractive index in the frequency span of 1.95–2.13, 2.30–2.41 and 4.63–4.87 GHz. Moreover, the effective medium ratio of the proposed NIM is considerable improved compared to previously reported multi-band NIMs. The proposed design paves the way for a new approach to design compact multi-band NIM which is free from disadvantages of both stacked cell methodology and split-ring resonator–wire topology.