Numerical studies on dual-band electromagnetic energy harvesting with double-ring split-ring resonators

Recently, split-ring resonators (SRRs) have been studied as the receiving element for electromagnetic energy harvesting, or RF energy harvesting, for its electrically small size and electric field concentration at resonance. However, traditional single-ring SRR studied in literature possesses intrinsic single bandwidth, unfit for collecting ambient multi-band RF energy. This paper proposes a double-ring SRR to harvest dual-band RF energy at 0.9 GHz and 2.4 GHz. Numerical simulation shows that the coupling between the two rings plays a critical role in the harvesting efficiency and the reasons are analyzed regarding to the electrical size of SRR and the electric field distribution. By utilizing the coupling, the double-ring SRR shows the effectiveness of dual-band energy harvesting, with a simulated efficiency of 84% at 0.9 GHz and 47% at 2.4 GHz.