Wideband Metamaterial Electromagnetic Energy Harvester With High Capture Efficiency and Wide Incident Angle

Abstract

This letter presents a wideband metamaterial electromagnetic (EM) energy harvester with high capture efficiency and wide incident angle. It is an array of novel resonators comprising metallic mirrored split rings and hollow cylinders. The impedance of the harvester is engineered to match with free space, so that the incident EM energy is captured with minimum reflection, and then channeled maximally to the ports through optimally positioned vias. The hollow cylinder works equivalently as a shunt capacitance in series with an inductance to lower the resonator's quality factor, which significantly enhances the bandwidth. The power harvesting mechanism is analyzed using both the transmission line model and full-wave simulation. A metamaterial harvester of 10 × 10 unit cells is designed, manufactured, and measured, achieving a capture efficiency of up to 97.3% at 2.45 GHz. A wide relative bandwidth of 16% with efficiencies above 90% is observed from 2.3 to 2.7 GHz. Within a wide incident angle range (92° on E-plane and 44° on H-plane), the harvester manages to capture more than half of the incident energy.