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 [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$PRF \leq (0 {\mathrm{ dBm}})$ </tex-math></inline-formula> ] 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.16~\mu \text{V}$ </tex-math></inline-formula> /s at 0 dBm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.125~\mu \text{V}$ </tex-math></inline-formula> /s at −6 dBm, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.08~\mu \text{V}$ </tex-math></inline-formula> /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. 

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

This paper presents multi-band and multi-location radio frequency (RF) survey for ambient energy harvesting As an alternative to costly spectrum analyzers, the survey was conducted using software defined radio for FM (88–108 MHz), cellular band (880 MHz) and Wi-Fi band (24 GHz) The power levels at three different locations in a tier-II smart city were recorded and plotted to get information on the available ambient RF power levels A full wave voltage quadrupler circuit (2-stage Dickson rectifier) was implemented to act as a rectifier and a voltage booster Two different types of antennae were used for capturing the ambient RF signals – wire antenna and capacitive loop antenna No impedance matching circuitry was employed and the ambient RF signals were used to charge up a capacitor connected to the rectifier output Capacitive loop antenna helped in achieving a peak capacitor voltage of 16 V and outperformed the simple wire antenna which provided a peak capacitor voltage of 13 V The charged capacitor was also used to drive an LED

Akhil Kumar Donka

Papers

Multi-band multi-location RF power survey and ambient RF energy harvesting circuit