A Novel RF Energy Harvester for Event-Based Environmental Monitoring in Wireless Sensor Networks

Perpetual energy source is the major research issue in the research community for energy-constrained wireless sensor network (WSN) and IoT applications. Radio-frequency (RF) energy harvesting has become a technology available round the clock due to increased communication activities. However, efficient RF energy harvesting for low-power regions [
$PRF \leq (0 {\mathrm{ dBm}})$
] is still a challenge. This article proposes a novel RF energy harvesting technique along with an intelligent dynamic energy flow control algorithm. The algorithm works with dedicated energy flow control hardware. It is also able to provide perpetual life time to the ultralow power sensor nodes. A close approximation of the size of the RF energy harvester array is proposed for the perpetual lifetime of the WSN node deployed with wake-up radio for event-based monitoring applications. The model is verified by mathematical analysis, simulation, and fabricated prototype results for the operability in the given system. It is found that the circuit provides improved dc output voltage over the previous benchmark at low power in the range of −20 to 0 dBm. The system can charge a 2.7 V, 350 F supercapacitor with the rate
$0.16~\mu \text{V}$
/s at 0 dBm,
$0.125~\mu \text{V}$
/s at −6 dBm, and
$0.08~\mu \text{V}$
/s at −20 dBm. To prove the utility of the proposed idea, an RF field survey is also conducted and found that the proposed circuit can harvest energy from high power region (≥ −6 dBm) for LTE850 and LTE 900 bands.