RF Energy Harvesting Applications Research Articles

PARAMETRIC ANALYSIS AND GAIN ENHANCEMENT OF PLANAR YAGI ANTENNA

In this paper, a Yagi-Uda planar antenna of frequency 2.4 GHz is designed and its characteristics are studied. The antenna is fabricated using FR4 Epoxy substrate material having a dielectric constant, εr = 4.4 and a thickness of 1.6 mm. The antenna is designed and simulated in HFSS software. This paper is focused to design an antenna with increased gain. This improvement in gain is implemented by reducing the back lobe with the usage of the reflector and enhancing the forward traveling wave by using the director. In this paper, the character study of patch antenna along with reflector and directors are investigated. The gain of the composite antenna is 3.8 dB, which is a 27% improvement over the basic patch antenna. This composite antenna can be used for a variety of applications like RF energy harvesting, WLAN, LTE, and many other medical applications.

A Planar Antenna on Flexible Substrate for Future 5G Energy Harvesting in Malaysia

This article presents a planar monopole antenna on flexible substrate for middle band 5G (3.5 GHz) application in Malaysia. The antenna has been designed and optimized for its gain and efficiency with an improved performance in contrast of flexible substrate-based other antennas. The antenna resonates at 3.53 GHz and it has a -10dB bandwidth of 545 MHz. The bending effects of this antenna on the S-parameter and gain have also been investigated. The antenna is able to suppress all the other frequency bands until 20 GHz. The designed antenna has been utilized with a newly designed rectifier to act as an rectenna at 3.5 GHz for RF energy harvesting applications. A reasonable amount of DC output voltage of 930 mV, and a Power Conversion Efficiency of 43.5% have been obtained while 0 dBm RF input power is delivered to the rectifier input terminal. Apart from the utilization as an energy harvester being connected with the proposed rectifier, the designed antenna on flexible substrate can also be employed to biomedical and sensor applications.

An Efficient Reconfigurable RF-DC Converter With Wide Input Power Range for RF Energy Harvesting

This paper presents a reconfigurable radio frequency to direct current (RF-DC) converter operating at 902 MHz frequency designed to efficiently harvest RF signals and convert into useable DC voltages for RF energy harvesting applications. The proposed scheme employs a dual-path, a series (lowpower) path and a parallel (high-power) path, to maintain high power conversion efficiency (PCE) over wide input power range. The dual-path is composed of two identical rectifier blocks utilizing internal threshold voltage cancellation (IVC) technique to efficiently compensate the threshold voltage of the transistors used as rectifying devices. An adaptive control circuit (ACC) consisting of a comparator, an inverter and three switches is used in the proposed scheme. The ACC activates the series path or the parallel path to maximize the harvested power based on the input power range. The proposed scheme is designed and fabricated in a 180 nm complementary metal-oxide semiconductor (CMOS) technology. The measurement results show that PCE of the proposed circuit is above 20% from -18 dBm to -5 dBm, maintaining 13-dB input power range with peak PCE of 33% at -8 dBm for 200 kΩ load resistance. The proposed circuit demonstrates -20.2 dBm sensitivity across 1 MΩ load resistance while producing 1 V output DC voltage.

A differential triple band antenna based Energy Harvesting System

A triple band differential rectenna for RF energy harvesting applications is proposed in this paper. The rectenna is designed to operate in frequency bands of universal mobile telecommunication service (2.1 GHz), lower WLAN/Wi- Fi (2.4– 2.48 GHz), and WiMAX (3.3–3.8 GHz). For designing the proposed rectenna, initially a differentially fed multiband slot antenna that works as the front-end receiving unit is designed, fabricated, and tested to check its performance. In the next step, a triple band differential rectifier is designed using the Villard voltage doubler where inter digital capacitors (IDCs) in lieu of lumped components are used. The full rectifier circuit comprising of the rectifying unit and impedance matching circuit is fabricated and tested to check its performance in the desired bands. The peak RF-dc conversion efficiency of 68% is obtained using the three-tone measurement. In the final stage, both antenna and the rectifier circuit are integrated through SMA connecter in order to implement the proposed rectenna.

A compact and efficient graphene FET based RF energy harvester for green communication

This paper presents a graphene field effect transistor (FET) based rectenna with substrate-integrated waveguide (SIW) broadband approach for RF energy harvesting application. The proposed structure of integrated rectenna consists of a graphene FET rectifier and an SIW antenna operating in the (S11 < −10 dB) range of 29–46 GHz. The peak gain of the SIW antenna observed is 8.12 dBi. In addition, a new matched circuit consisting of microstrip line and butterfly stub (without using any lumped elements) is designed. The matched circuit provides a miniaturized block by reducing the size and eliminating parasitic reactance in the integrated rectenna. The proposed rectenna is implemented and fabricated using two superimposed layers: RT/duroid 5880 and graphene substrate with a compatible approach. A measured conversion efficiency of 80.32% is obtained. The dimensions of the proposed antenna and rectifier are 3.2 × 3.2 × 0.4 mm3 and 3.2 × 10 × 0.4 mm3, respectively. The proposed rectenna covers Ka- and Q-band applications and could be a potential candidate for contemporary energy harvesting systems.

A 2.4 GHz Rectenna Based on a Solar Cell Antenna Array

Combined solar and radio frequency (RF) harvesting systems are drawing attention by offering self-powered ability to low-power devices, an essential aspect to the success of the Internet of Things. One of the main challenges of these harvesting systems is to improve rectennas efficiency by optimizing the individual energy collection and conversion capacity of each source. To overcome this issue, this letter presents a novel 2.4-GHz rectenna structure for solar and radio frequency energy harvesting applications based on a coplanar antenna array integrated with multicrystalline solar cells, whose aluminum rear terminals are used as radiators for the antenna array. The results obtained by simulations and measurements show that it is possible to collect energy from two different types of sources in a complementary manner, using the rectenna design proposed, making it possible to feed low-power devices remotely.

Integrated cmos rectifier for rf-powered wireless sensor network nodes

This article presents a review of the CMOS rectifier for radio frequency energy harvesting application. The on-chip rectifier converts the ambient low-power radio frequency signal coming to antenna to useable DC voltage that recharges energy to wireless sensor network (WSN) nodes and radiofrequency identification (RFID) tags, therefore the rectifier is the most important part of the radio frequency energy harvesting system. The impedance matching network maximizes power transfer from antenna to rectifier. The design and comparison between the simulation results of one- and multi-stage differential drive cross connected rectifier (DDCCR) at the operating frequencies of 2.44GHz, and 28GHz show the output voltage of the multi-stage rectifier doubles at each added stage and power conversion efficiency (PCE) of rectifier at 2.44GHz was higher than 28GHz. The (DDCCR) rectifier is the most efficient rectifier topology to date and is used widely for passive WSN nodes and RFID tags.

A dual‐band high‐gain quasi‐Yagi antenna with split‐ring resonators for radio frequency energy harvesting

AbstractThis article presents a quasi‐Yagi antenna operating with high gain at two frequency bands. Compared with a conventional Yagi antenna, the proposed antenna is designed by integrating a pair of printed split‐ring resonators (SRRs) into the antenna layout. The SRRs introduce a new resonant frequency band and the antenna gain remains high at both the bands. The simulated and measured results show that the antenna is well matched while the antenna gain is 6 and 5.80 dBi at the GSM1800 and ISM2450 bands, respectively. The proposed antenna is compact and efficient and achieves high gain so that it could be successfully used in various wireless communication and radio frequency energy harvesting applications.

Enhanced radio frequency rectifier with a power splitting/combining topology for wireless energy transfer and harvesting

Power splitting of the input radio frequency (RF) signal is used to improve the efficient power range of a RF rectifier. Direct current (dc) power at the output of every rectifying branch is then combined over a resistive load and thus resulting in a single dc output. The enhancement in efficient power range, over which the power conversion efficiency (PCE) remains ≥ 50%, is determined to be 2.8 dB. The article starts by a theoretical analysis that addresses the negative effects of the diode's breakdown voltage, formulates an equation that predicts the maximum output dc voltage at saturation, and introduces a method that can improve the PCE of a typical shunt-type diode rectifier at low power levels. As a result, a rectifying system is designed and tested as a proof of concept. The proposed circuit, with the enhanced power range, is designed to operate within the power span from -10 dBm up until 10 dBm. Such system is suitable for operation in RF wireless energy transfer and energy harvesting applications.

A wideband rectifier array on dual‐polarized differential‐feed fractal slotted ground antenna for RF energy harvesting

This article reports a novel wideband rectenna for RF energy harvesting applications. A wideband fractal slotted ground antenna (SGA) is adopted. The operating frequency bands of the antenna are GSM, UMTS, Wi-Fi, and LTE2600/4G bands. The antenna is fed by a dual-polarized and differential-feed (DP-DF) microstrip lines disposed with an angle of 90° each relative to the other. The feed lines are etched on the bottom side of the substrate and connected to an array of four wideband RF-to-DC rectifiers. A nonuniform transmission lines filter ensures wideband behavior for each rectifier. The rectenna performances are simulated and measured. The experiments show an output DC voltage of 1 V at a power density of 26.6 μW/cm2 over the frequency band of operation with a peak efficiency of 50%. The proposed rectenna is suitable for energy harvesting applications in urban environments.

Investigation of Micromachined Antenna Substrates Operating at 5 GHz for RF Energy Harvesting Applications.

This paper investigates micromachined antenna performance operating at 5 GHz for radio frequency (RF) energy harvesting applications by comparing different substrate materials and fabrication modes. The research aims to discover appropriate antenna designs that can be integrated with the rectifier circuit and fabricated in a CMOS (Complementary Metal-Oxide Semiconductor)-compatible process approach. Therefore, the investigation involves the comparison of three different micromachined antenna substrate materials, including micromachined Si surface, micromachined Si bulk with air gaps, and micromachined glass-surface antenna, as well as conventional RT/Duroid-5880 (Rogers Corp., Chandler, AZ, USA)-based antenna as the reference. The characteristics of the antennas have been analysed using CST-MWS (CST MICROWAVE STUDIO®—High Frequency EM Simulation Tool). The results show that the Si-surface micromachined antenna does not meet the parameter requirement for RF antenna specification. However, by creating an air gap on the Si substrate using a micro-electromechanical system (MEMS) process, the antenna performance could be improved. On the other hand, the glass-based antenna presents a good S11 parameter, wide bandwidth, VSWR (Voltage Standing Wave Ratio) ≤ 2, omnidirectional radiation pattern and acceptable maximum gain of >5 dB. The measurement results on the fabricated glass-based antenna show good agreement with the simulation results. The study on the alternative antenna substrates and structures is especially useful for the development of integrated patch antennas for RF energy harvesting systems.

Novel UWB printed metamaterial microstrip antenna based organic substrates for RF-energy harvesting applications

In this paper, an intensive study is proposed to recycle the organic materials use for microwave applications including RF-energy harvesting. Thus, the Iraqi Palme Tree Remnants (IPTR) is exemplified for this study to create dielectric substrates. The main texture of the fabricated substrates is IPTR mixed with Nickel Oxide Nanoparticles (NONP) hosted in Polyethylene (PE) to be called INP substrates. Nevertheless, a metamaterial (MTM) printed antenna on the proposed substrate is fabricated by material printer with Sliver Nanoparticles Conductive Ink (SNPCI). The antenna performance is tested numerically/experimentally in terms of S11 spectrum and radiation patterns. It is found excellent matching bandwidths at 2.45 GHz and 5.8 GHz frequencies with acceptable gains of 1.56 dBi and 2.48 dBi, respectively. The proposed antenna bandwidth is found to start from 2.4 GHz up to more than 10 GHz. The maximum achieved gain and efficiency are found about 3.456 dBi and 78% at 9 GHz. For this, the proposed antenna provides novel performance with ultimate antenna size reduction due to the introduction of the MTM based the proposed INP substrate. Finally, the harvested RF energy by the fabricated antenna is measured and found about 15 mV with a conversation efficiency of 85% at 2.45 GHz and 17.5 mV with a conversion efficiency of 91% at 5.8 GHz.

A modified Hilbert fractal resonator based rectenna design for GSM900 band RF energy harvesting applications

This article proposes a novel rectenna design based on modified Hilbert fractal shaped microstrip antenna and Villard voltage doubler rectifying circuit for RF energy harvesting applications operating at Global System for Mobile Communications (GSM) 900 MHz band. The energy harvesting antenna is numerically optimized and fabricated on a Rogers RO4003 substrate of thickness 1.52 mm with a compact overall physical sizes of 80 mm × 82 mm (λ0/4.16 × λ0/4.06). Various geometric parameters and circuit component values of the proposed energy harvesting system are optimized in order to achieve a matched input impedance with good radiation performance of high gain for the input power level less than −20 dBm. The numerical and experimental results point out the technical potential of the proposed rectenna design to be utilized in DC power supply modules of low voltage, low power electronic devices.

Ultrathin dual-layer triple-band flexible microwave metamaterial absorber for energy harvesting applications

An ultrathin dual-layer flexible metamaterial absorber with triple-band for RF energy harvesting applications has been reported in this article. The sub-wavelength unit cell of the proposed absorber is composed of six distinct concentric annular having outer circumference of ring and octagonal inner circumference. The metallic resonators are constructed from copper foil self-adhesive tape which are affixed on flexible neoprene rubber sheet terminated by metal ground plate. The proposed absorber prototype is ultrathin and compact with the thickness less than 0.037λ0 and cell size less than 0.2λ0 at the lower absorption frequency of 1.75 GHz. Flexible dual-layer absorber exhibits triple absorption peaks of 96.91%, 96.41% and 90.12% at 1.75 GHz, 2.17 GHz and 2.6 GHz with full width at half maximum (FWHM) bandwidth of about ~6.5%. The RF performance of proposed absorber is numerically computed for different polarization and incidence angle variations. The absorption value is above 76% for the oblique incidence angle up to 45° in TE mode operation, whereas the absorption value is 94% for oblique incidence angle up to 60° in TM mode operation. The measured outcomes are in agreement with the numerically calculated results. The energy harvesting potential of the proposed absorber structure is numerically confirmed by the resulting improved RF absorption value in dependence to different resistive loading of the polarization insensitive unit cells.

Design of Quad Band Microstrip Patch Antenna for Electromagnetic Energy Harvesting Applications

In this paper, a modified circular microstrip patch antenna is simulated and fabricated for RF energy harvesting applications. Energy harvesting technologies have risen in term of technical developments gradually recently because of the limitation of energy storage and wired power supply. This paper focuses on quad RF energy harvesting in the operating frequency ranges 2.1 GHz, 2.4 GHz, 2.6 GHz and 5.8 GHz emitting from wi-fi, Wimax, LTE, 3G and 4G. The receiving antenna picking up the radio signal in the aforementioned frequencies then converts it from a radiated electromagnetic wave into an alternating signal and, via rectifier, it is converted later into DC voltage. This voltage can be stored inside battery or the load may be fed directly. In this paper, SMD capacitors resistors and Schottky diode model SMS7630-005LF were chosen in the construction of the rectifier circuit due to their low forward voltage between between 0.15 to 0.45 V, fast switching action and small size.

Design of wideband microstrip power divider/combiner with input and output impedance matching for RF energy harvesting applications

Lately, it has been seen that wireless communication systems have been more developed and there has been a huge demand for multi-spectral transactions. Using circuits for more than one function is a serious requirement in communication technology. Especially, it expected from RF output stages to show the same performance on more than one frequency. To that end, it is required to produce a solution with wideband designs. In this study, a novel power divider/combiner design with a layered conic line has been investigated for the RF energy harvesting applications. The center frequency was set at 2 GHz and concluded with three different designs. In each design, bandwidth and S parameter characteristics were compared according to the number of layers of the transmission, and it was observed that as the number of layers increases, the bandwidth also increases. According to the design result, triple layer Wilkinson power divider was selected to connect to Villard voltage doubler circuit. The Wilkinson power combiner circuit inputs were given between −10 dBm and 5 dBm input power. As a result, when low input power was given, efficiency was observed about 70%.

Design and performance analysis of broadband rectenna for an efficient RF energy harvesting application

This article proposes the design of coplanar waveguide (CPW) fed broadband rectenna for radio frequency (RF) energy harvesting application. The rectenna is designed to operate in the industrial, scientific, and medical (ISM) frequency band of 5.8 GHz. For designing the proposed rectenna, polytetrafluoroethylene (PTFE) dielectric material was used to design, fabricate the CPW fed slot antenna. It was observed that the proposed antenna exhibits the |S11| of −23.43 dB and achieves the peak antenna gain of 8.56 dBi at 5.8 GHz. Secondly, the CPW fed rectifier circuit which comprises of the matching circuit, rectifying unit, and filter was designed. The measured results showed that the |S11| of −19 dB and it was perfectly matched with 50 Ω impedance. Finally, the rectenna was designed by integration of antenna with rectifier circuit. The simulated results showed the maximum RF to direct current (DC) conversion efficiency and the output DC voltage of 88% and 445 mV at the load resistance of 1 kΩ. The measured results show the maximum RF to DC conversion efficiency of 73.4% with the output DC voltage of 540 mV at the load resistance of 1 kΩ.

Design of Triple Band Differential Rectenna for RF Energy Harvesting

A triple band differential rectenna for RF energy harvesting applications is proposed in this paper. The rectenna is designed to operate in frequency bands of universal mobile telecommunication service (2.1 GHz), lower WLAN/Wi-Fi (2.4–2.48 GHz), and WiMAX (3.3–3.8 GHz). For designing the proposed rectenna, first a differentially fed multiband slot antenna that works as the front-end receiving unit is designed, fabricated, and tested to check its performance. It is observed that a peak antenna gain of 7, 5.5, and 9.2 dBi is achieved at 2, 2.5, and 3.5 GHz, respectively. In the next step, a triple band differential rectifier is designed using the Villard voltage doubler where interdigital capacitors (IDCs) in lieu of lumped components are used. The full rectifier circuit comprising of the rectifying unit and impedance matching circuit is fabricated and tested to check its performance in the desired bands. The peak RF-dc conversion efficiency of 68% is obtained using the three-tone measurement. In the final stage, both antenna and the rectifier circuit are integrated through SMA connecter in order to implement the proposed rectenna. Measurement of the proposed rectenna shows an approximate maximum efficiency of 53% at 2 GHz, 31% at 2.5 GHz, and 15.56% at 3.5 GHz.

Low profile microstrip fed printed antenna for portable RF energy harvesting system

This work presents, a printed wideband microstrip antenna that can be used for portable RF energy harvesting applications. The antenna is designed, simulated and validated using 3D electromagnetic HFSS simulator. The targeted frequency band of operations are from 0.825 GHz to 1.05 GHz for catering GSM/3G wireless applications. Following the antenna design in the HFSS software, the structure has been fabricated on low cost substrate FR4 and the structure performance is analyzed experimentally. The achieved wideband, omni directional patterns with constant gain monopole antenna can be suitable for all portable system applications.

A multi‐band rectifier with modified hybrid junction for RF energy harvesting

AbstractThis article presents a novel multi‐band rectifier utilizing modified hybrid structure for radio frequency (RF) energy harvesting. The proposed multi‐band rectifier consists of a modified hybrid junction and three rectifying branches. The rectifying branches are placed inside the modified hybrid to reduce the layout size. The proposed multi‐band rectifier is designed for GSM‐1800, UMTS‐2100, and Wi‐Fi bands. Measured peak efficiency of the proposed rectifier reaches 61.7% at 9 dBm input power level. The results show a good overall performance on operation bands, efficiency, output voltage, and layout size. The proposed rectifier can be used for various RF energy harvesting applications, especially in the multi‐source condition.