RF Energy Harvesting Applications Research Articles

Design of a ferrite rod antenna for harvesting energy from medium wave broadcast signals

Radio frequency (RF) energy harvesting is an emerging technology that has the potential to eliminate the need for batteries and reduce maintenance costs of sensing applications. The antenna is one of the critical components that determines its performance and while antenna design has been well researched for the purpose of communication, the design for RF energy harvesting applications has not been widely addressed. The authors present an optimised design for such an antenna for harvesting energy from medium wave broadcast transmis- sions. They derive and use a model for computing the optimal antenna configuration given application requirements on output voltage and power, material costs and physical dimensions. Design requirements for powering autonomous smart meters have been considered. The pro- posed approach was used to obtain the antenna configuration that is able to deliver 1 mW of power to 1 kΩ load at a distance of up to 9 km, sufficient to replace batteries on low-power sensing applications. Measurements using a prototype device have been used to verify the authors simulations.

Design of low power RF to DC generator for energy harvesting application

This paper describes the design of a voltage doubler with matching circuit using Schottky diode HSMS-2850 and microstrip rectangular patch antenna array for RF energy harvesting application. Microstrip rectangular antenna array and two stage voltage doubler or charge pump circuit are designed for capturing directed electromagnetic energy and convert into suitable DC voltage. Simulation results show that a DC voltage of 0.747 V can be achieved at −10dBm input energy level at 2.4 GHz when load is 20 Kohm. This paper also describes microstrip rectangular patch antenna array (2x2) for increase the input energy level at 2.4 GHz frequency.

A Battery-Free 217 nW Static Control Power Buck Converter for Wireless RF Energy Harvesting With $\alpha $-Calibrated Dynamic On/Off Time and Adaptive Phase Lead Control

A battery-free nano-power buck converter with a proposed dynamic on/off time (DOOT) control can achieve high conversion efficiency over a wide load range. The DOOT control can predict the on/off time at different input voltages without a power consuming zero current detection (ZCD) circuit, as well as suppress static power in idle periods. To adapt to the fluctuations in a harvesting system, the proposed α-calibration scheme guarantees accurate ZCD over process, voltage variation, and temperature (PVT) in the DOOT to improve power conversion efficiency. Furthermore, the adaptive phase lead (APL) mechanism can improve inherent propagation delay attributable to low-power and non-ideal comparator, thus improving load regulation by a maximum of 30 mV. The test chip was implemented in 0.25-μm CMOS process with a die area of 0.39 mm2. Experimental results showed 95% peak efficiency, low static power of 217 nW and good load regulation of 0.1 mV/mA, which are suitable for RF energy harvesting applications.