A compact hybrid solar and electromagnetic energy harvester at 2.45 GHz microstrip rectenna

This paper presents a compact rectenna integrated with a packaged solar cell to convert a hybrid (solar + electromagnetic) energy to DC energy. The packaged solar cell used as the substrate is sandwiched between a meshed patch and a rectifying circuit. Based on particle swarm algorithm, the meshed patch with high transparency (96.2 % transmittance) is mounted on the surface of the solar cell. By using a copper rod, the high-efficient rectifying circuit is connected with the meshed patch through the solar cell. Due to the high-integrated hybrid energy harvester, the solar and radio frequency (RF) energies can be absorbed and converted to DC power separately or simultaneously. The measured maximum RF-DC conversion efficiency of the rectenna acquires 73 % under the input power of the antenna of 17 dBm, and the maximum DC power of 60.6 mW is generated when the solar cell is illuminated with standard global AM1.5 illumination conditions. The measured DC combining efficiency of 96.8 % is achieved from the hybrid solar rectenna, with the optimal load of 400 omega. Furthermore, the design method is extended to harvesting ambient electromagnetic energy, and a low-power rectifying circuit with conversion efficiency of 59.6 % at input power of-10 dBm is designed.