Design and experimental validation of a compact dual band double negative metamaterial for energy harvesting applications.

This work presents a compact double-negative (DNG) metamaterial (MM) design optimized for energy harvesting (EH) applications. Current EH designs often face challenges such as large physical size, narrow operational bandwidth, and low efficiency. To overcome these limitations, we propose a novel MM structure composed of two concentric circular and two concentric rectangular resonators, each featuring 45-degree inclined gaps to enhance electromagnetic coupling and interaction. These resonators are fabricated from annealed copper and symmetrically arranged on a Rogers RT 5880 substrate with a back-coated copper layer to maximize absorption and minimize transmission losses. A key characteristic of the proposed structure is its DNG properties, meaning it simultaneously exhibits negative permittivity and negative permeability, which result in a negative refractive index. This unique behaviour enables electromagnetic waves to propagate unconventionally, enhancing wave absorption and EH performance. The structure demonstrates these DNG properties at dual resonance frequencies of 4.4 GHz and 5.7 GHz, achieving near-perfect absorption. A 3 × 3 array of the proposed MM further enhances efficiency, achieving 97% and 98% Energy Harvesting Efficiency (EH-E) at these frequencies. To validate the performance of the design, we conducted experimental measurements, which showed a strong correlation with simulation results, confirming the reliability of the proposed structure. These findings underscore the potential of the compact MM design for advanced applications in EM wave manipulation and high-efficiency EH.