A Quad-Band Stacked Hybrid Ambient RF-Solar Energy Harvester With Higher RF-to-DC Rectification Efficiency

This article addresses the design and implementation of a novel quad-band electromagnetic (EM) and solar energy scavenging system, ensuring energy harvesting from ambient RF environment with excellent “cold start” power level. The proposed scavenger consists of a single port quad-band rectangular slot antenna, power film solar cell, a quad-band RF- to-DC converter, a microcell power management module, and a battery. The harmonic balance of EM solver is used to design and maximize the RF- to - DC rectification efficiency with the combination of the antenna and the solar cell. The power film solar cell is placed in the middle of the antenna with positive and negative edges connected to the top and bottom layer of the antenna so that total harvested energy passes through the rectifier and forms an ambient hybrid energy harvesting system. One significant benefit of this method is the utilization of the antenna free space for the effective area of the power film. Another important contribution is the employment of multiband antennas for increasing the total ambient RF scavenged energy. Besides, a cost-effective and flexible FR4 substrate and a micropower film solar cell are used to make it conformal and cheaper. The prototype of hybrid harvester demonstrated that with 360 lux ambient light intensity, at the solar cell can generate 0.109 V energy while the harvester can attain an extra 5% - 48% energy with ambient RF input level variation from −15 to −20 dBm. The rectifier circuit achieves 74.5% RF-to-DC rectification efficiency for the value of load resistance 2.7
$\text{k}\Omega $
. These performances depict that the proposed multiband ambient hybrid RF-solar power scavenger can raise the scavenged power level and offer energy multiplicity.