Efficiency in RF energy harvesting systems: A comprehensive review

Electromagnetic energy harvesting holds a promising future for energizing low power electronic devices in wireless communication circuits. This article presents an RF energy harvesting system that can harvest energy from the ambient surroundings at the downlink radio frequency range of GSM-900 band. The harvesting system is aimed to provide an alternative source of energy for energizing low power devices. The system design consists of three modules: a single wideband 377› E-shaped patch antenna, a pi matching network and a 7-stage voltage doubler circuit. These three modules were fabricated on a single printed circuit board. The antenna and Pi matching network have been optimized through electromagnetic simulation software, Agilent ADS 2009 environment. The uniqueness of the system lies in the partial ground plane and the alignment of induced electric fleld for maximum current ∞ow in the antenna that maximizes the captured RF energy. The design and simulation of the voltage doubler circuit were performed using Multisim software. All the three modules were integrated and fabricated on a double sided FR 4 printed circuit board. The DC voltage obtained from the harvester system in the fleld test at an approximate distance of 50m from GSM cell tower was 2.9V. This voltage was enough to power the STLM20 temperature sensor.

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Design of RF energy harvesting system for energizing low power devices

A novel coplanar waveguide-fed rectenna with high efficiency is proposed and implemented in this paper for 2.45-GHz Bluetooth/ wireless local area network applications. The antenna has compact dimensions of 18 mm $\times \,\, 30$ mm, which is simulated and manufactured using a low-cost FR4 substrate with a thickness of 1.6 mm. A tuning stub technique with rectangular slots is used for better impedance matching and enhancing the impedance bandwidth of the antenna with a peak gain of 5.6 dB. The proposed novel antenna for RF energy harvesting applications exhibits dipolelike radiation pattern in $H$ -plane and omnidirectional pattern in $E$ -plane with improved radiation efficiency. Single-stage Cockcroft–Walton rectifier with L-shaped impedance-matching network is designed in advance design system and fabricated on FR4 substrate. The dc output of the rectenna is measured as 3.24 V with a load resistance of 5 $\text{k}\Omega $ . A simulated peak conversion efficiency of 75.5% is attained, whereas the measured one is observed to be 68% with an input signal power of 5 dBm at 2.45 GHz.

A Compact Rectenna System With High Conversion Efficiency for Wireless Energy Harvesting

Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478-496 and 852-869 MHz) and exhibits favorable impedance matching over a broad input power range (-40 to -10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of -10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments.

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Multi-service highly sensitive rectifier for enhanced RF energy scavenging

Energy harvesting (EH) or scavenging is recognized as harvesting energy from ambient energy sources in the surrounding environment. This paper reports a literature review on radio frequency (RF) EH using different metasurface/metamaterial structures based on split-ring resonators (SRRs), electric inductive–capacitive (ELC) resonators, square-patch unit cells, square-ring unit cells, etc. The essential parameters in rectifying antenna (rectenna) design are included, such as receiving antenna efficiency, conversion efficiency, dimensions, supporting substrate properties, frequency band, and overall performance, etc. It is noted that rectenna design using conventional antennas such as microstrip antennas, monopole antennas, slot antennas, dielectric resonator antennas, etc. suffers from low power conversion efficiency with larger size. To overcome the above-mentioned constraints and enhance the conversion efficiency with smaller size, metasurface/metamaterial structures are used as EH collectors. An introduction to EH is discussed, followed by an overview of energy sources in the ambient environment. Several hypothetical and experimental studies on metasurface-based EH systems are summarized.

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A Comprehensive Review of Metasurface Structures Suitable for RF Energy Harvesting

This paper presents an optimization of the voltage doubler stages in an energy conversion module for Radio Frequency (RF) energy harvesting system at 900 MHz band The function of the energy conversion module is to convert the (RF) signals into direct-current (DC) voltage at the given frequency band to power the low power devices/circuits The design is based on the Villard voltage doubler circuit A 7 stage Schottky diode voltage doubler circuit is designed, modeled, simulated, fabricated and tested in this work Multisim was used for the modeling and simulation work Simulation and measurement were carried out for various input power levels at the specified frequency band For an equivalent incident signal of –40 dBm, the circuit can produce 3mV across a 100 k? load The results also show that there is a multiplication factor of 22 at 0 dBm and produces DC output voltage of 50 V in measurement This voltage can be used to power low power sensors in sensor networks ultimately in place of batteries

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Optimization of the Voltage Doubler Stages in an RF-DC Convertor Module for Energy Harvesting

The design of voltage multiplier module used for energy harvesting system from ambient at downlink radio frequency range (9352 MHz-9598 MHz) of GSM-900 is presented The function of this voltage multiplier circuit is to convert the RF energy signal into DC voltage that can be used to energize the low power electronic devices The design was based on the Villard voltage multiplier circuit A 4-stage Schottky diode voltage multiplier circuit was designed, modeled, simulated, fabricated and tested for its performance Multisim was used for the modeling and simulation work Simulation and practical tests were carried out for various input power levels at the specified frequency band The RF input power levels verses the output voltages at the nodes of the Villard network were recorded The input for the voltage multiplier module was fed through an efficient matching network from an RF energy harvesting antenna which is designed at 377 Ω impedance For a received signal of −27dBm (199) μW at the antenna modules produce a DC output voltage of 21 V across 100 kΩ load

Design of an RF-DC conversion circuit for energy harvesting

A novel 377 Ω patch antenna operating at GSM 900 downlink band for RF energy harvesting is proposed and analyzed in this paper. The designed antenna consists of a normal patch with two steps incorporated at the appropriate position to enhance its bandwidth. The antenna is designed and tested in Agilent advance design systems ADS environment and constructed on a FR4 substrate. The antenna yields an impedance bandwidth of 34.35% (325 MHz) at 946 MHz centre frequency with a return loss S 11 of •29.22dB and gain of 5.2 dBi. The proposed patch antenna is suitable for ambient RF energy harvesting at downlink frequency band of GSM 900 as demonstrated by simulation and experimental results. The measured results closely agree with the simulated results.

Design of a 377 Ω patch antenna for ambient RF energy harvesting at downlink frequency of GSM 900

The design of a 377 Ω E-shaped patch antenna with partial ground plane is presented and discussed in this article. Two parallel slots are introduced into the conventional patch antenna, and it was investigated by the currents through the patch to enhance its bandwidth. The antenna is designed, fabricated, and measured for downlink frequency band of GSM 900, which shows an impedance bandwidth of 29.03% (277 MHz) at 954 MHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:569–573, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26607

K. K. A. Devi

Papers

Design of RF energy harvesting system for energizing low power devices

Optimization of the Voltage Doubler Stages in an RF-DC Convertor Module for Energy Harvesting

Design of an RF-DC conversion circuit for energy harvesting

Design of a 377 Ω patch antenna for ambient RF energy harvesting at downlink frequency of GSM 900

Design of a wideband 377 Ω E-shaped patch antenna for RF energy harvesting