Integrated Cooperative Ambient Power Harvester Collecting Ubiquitous Radio Frequency and Kinetic Energy

Abstract

An integrated cooperative harvester capable of collecting both electromagnetic [(principally radio frequency (RF)] and kinetic energy simultaneously is proposed and studied in this paper. One single substrate board is demonstrated to accommodate and integrate an electromagnetic kinetic generator, an F-shaped antenna, and a rectifying circuit, having a compact credit-card size. Cooperative harvesting mode enables a significant enhancement of the diode's power conversion efficiency (PCE) and also greatly strengthening the resilience of harvester at the same time. Measured results suggest that SMS7630 and HSMS-2850-based cooperative harvesters can increase dc output power by 50% to around 100% when both injecting power sources exhibit below -37 dBm with reference to the total added amount of dc power harvested directly from separate RF and kinetic excitation modes. A closed-form method is proposed and used to predict the enhanced efficiency performance of the cooperative harvester within a low power range of interest (from -50 to -30 dBm). Our analysis highlights the roles of the diode's nonlinear junction resistance and capacitance. Good agreements are observed when comparing the analysis results with harmonic balance simulations by ADS. Furthermore, this method is carefully verified by measured results of two different diode-based harvesters. Measured dc output power rectified from cooperative harvesting mode is reported to be 1.16 and 1.97 times larger with SMS7630 and HSMS-2850, respectively, when both power sources are -40 dBm, compared to the conventional single RF harvesting mode. The proposed cooperative harvester with its strong resilience is highly suitable for ambient power harvesting in an ever-changing environment.