An Investigation of Wideband Rectennas for Wireless Energy Harvesting

This paper is focused on a wireless energy harvesting system using a rectifying antenna (rectenna). The proposed device consists of a wideband cross-dipole antenna, a microwave low-pass filter and a doubling rectifying circuit using Shottcky diodes as rectifying elements. Previously, a few of wideband rectennas have been investigated at 1.7 to 2.5 GHz. The originality of this paper is on the new wideband rectenna design which can harvest the ambient radio frequency (RF) power at 1.7 to 2.5 GHz. In this system, a new wideband cross dipole is designed and used to achieve the required bandwidth and duel-polarization. In addition, the voltage doubling rectifying circuit is optimized to achieve the best performance at power density levels 2 which are typical in urban environments. The characteristics of the proposed rectenna over the desired frequency range are investigated, and the integrated rectenna is simulated, made and tested for low input power densities from 5 to 200 μW/cm2. The simulation and measurement results of the rectenna are compared and a good agreement is achieved. The results demonstrate that the maximum rectenna conversion efficiency is nearly 57% around 1.7 GHz and over 20% over the wideband of interest for the incident power density of 120 μW/cm2. It is noted that the impedance matching is one of the main factors affecting the rectenna energy conversion efficiency. This new wideband rectenna has great potential to harvest wireless energy in GSM/3G/4G and ISM 2.4 GHz bands.

X-BAND CIRCULARLY POLARIZED RECTENNAS FOR MICROWAVE POWER TRANSMISSION APPLICATIONS

Circularly polarized rectennas operating at X-band are studied in this paper. The quasi-square patches fed by aperture coupling are used as the circularly polarized receiving antennas, which are easily matched and integrated with the circuits of rectennas. The double-layer structure not only minimizes the size of the rectennas but also decreases the effects of the circuits on the an- tenna. The receiving elements have broader bandwidth and higher gain than the single-layer patches. Two rectennas operating at 10GHz are designed, fabricated and measured. The voltage of 3.86V on a load of 200? is measured and a high RF-DC conversion efficiency of 75% is obtained at 9.98GHz. It is convenient for this kind of rectennas to form large arrays for high power applications.

High Performance Electrically Small Huygens Rectennas Enable Wirelessly Powered Internet of Things Sensing Applications:A Review

Far-field wireless power transfer(WPT)is a major breakthrough technology that will enable the many anticipated ubiquitous Internet of Things(IoT)applications associated with fifth generation(5G),sixth generation(6G),and beyond wireless ecosystems.Rectennas,which are the combination of rectifying circuits and antennas,are the most critical components in far-field WPT systems.However,compact application devices require even smaller integrated rectennas that simultaneously have large electromagnetic wave capture capabilities,high alternating current(AC)-to-direct current(DC)(AC-to-DC)conversion efficiencies,and facilitate a multifunctional wireless performance.This paper reviews various rectenna miniaturization techniques such as meandered planar inverted-F antenna(PIFA)rectennas;miniaturized monopole-and dipole-based rectennas;fractal loop and patch rectennas;dielectric-loaded rectennas;and electrically small near-field resonant parasitic rectennas.Their performance characteristics are summarized and then compared with our previously developed electrically small Huygens rectennas that are proven to be more suitable for IoT applications.They have been tailored,for example,to achieve batteryfree IoT sensors as is demonstrated in this paper.Battery-free,wirelessly powered devices are smaller and lighter in weight in comparison to battery-powered devices.Moreover,they are environmentally friendly and,hence,have a significant societal benefit.A series of high-performance electrically small Huygens rectennas are presented including Huygens linearly-polarized(HLP)and circularly-polarized(HCP)rectennas;wirelessly powered IoT sensors based on these designs;and a dual-functional HLP rectenna and antenna system.Finally,two linear uniform HLP rectenna array systems are considered for significantly larger wireless power capture.Example arrays illustrate how they can be integrated advantageously with DC or radio frequency(RF)power-combining schemes for practical IoT applications.

Highly Flexible Graphene-Film-Based Rectenna for Wireless Energy Harvesting

Herein,we report the design,fabrication,and performance of two wireless energy harvesting devices based on highly flexible graphene macroscopic films(FGMFs).We first demonstrate that benefiting from the high conductivity of up to 1×10^(6)S m^(-1)and good resistive stability of FGMFs even under extensive bending,the FGMFs-based rectifying circuit(GRC)exhibits good flexibility and RF-to-DC efficiency of 53%at 2.1 GHz.Moreover,we further expand the application of FGMFs to a flexible wideband monopole rectenna and a 2.45 GHz wearable rectenna for harvesting wireless energy.The wideband rectenna at various bending conditions produces a maximum conversion efficiency of 52%,46%,and 44%at the 5th Generation(5G)2.1 GHz,Industrial Long-Term Evolution(LTE)2.3 GHz,and Scientific Medical(ISM)2.45 GHz,respectively.A 2.45 GHz GRC is optimized and integrated with an AMC-backed wearable antenna.The proposed 2.45 GHz wearable rectenna shows a maximum conversion efficiency of 55.7%.All the results indicate that the highly flexible graphene-film-based rectennas have great potential as a wireless power supplier for smart Internet of Things(loT)applications.

Resonator Rectenna Design Based on Metamaterials for Low-RF Energy Harvesting

In this paper,the design of a resonator rectenna,based on metamaterials and capable of harvesting radio-frequency energy at 2.45 GHz to power any low-power devices,is presented.The proposed design uses a simple and inexpensive circuit consisting of a microstrip patch antenna with a mushroom-like electromagnetic band gap(EBG),partially reflective surface(PRS)structure,rectifier circuit,voltage multiplier circuit,and 2.45 GHzWi-Fi module.The mushroom-like EBG sheet was fabricated on an FR4 substrate surrounding the conventional patch antenna to suppress surface waves so as to enhance the antenna performance.Furthermore,the antenna performance was improved more by utilizing the slotted I-shaped structure as a superstrate called a PRS surface.The enhancement occurred via the reflection of the transmitted power.The proposed rectenna achieved a maximum directive gain of 11.62 dBi covering the industrial,scientific,and medical radio band of 2.40–2.48 GHz.A Wi-Fi 4231 access point transmitted signals in the 2.45 GHz band.The rectenna,located 45◦anticlockwise relative to the access point,could achieve a maximum power of 0.53μW.In this study,the rectenna was fully characterized and charged to low-power devices.

Scavenging Microwave Wireless Power:A Unified Model,Rectenna Design Automation,and Cutting-Edge Techniques

While sufficient review articles exist on inductive short-range wireless power transfer(WPT),long-haul microwave WPT(MWPT)for solar power satellites,and ambient microwave wireless energy harvesting(MWEH)in urban areas,few studies focus on the fundamental modeling and related design automation of receiver systems.This article reviews the development of MWPT and MWEH receivers,with a focus on rectenna design automation.A novel rectifier model capable of accurately modeling the rectification process under both high and low input power is presented.The model reveals the theoretical boundary of radio frequency-to-direct current(dc)power conversion efficiency and,most importantly,enables an automated system design.The automated rectenna design flow is sequential,with the minimal engagement of iterative optimization.It covers the design automation of every module(i.e.,rectifiers,matching circuits,antennae,and dc–dc converters).Scaling-up of the technique to large rectenna arrays is also possible,where the challenges in array partitioning and power combining are briefly discussed.In addition,several cutting-edge rectenna techniques for MWPT and MWEH are reviewed,including the dynamic range extension technique,the harmonics-based retro-directive technique,and the simultaneous wireless information and power transfer technique,which can be good complements to the presented automated design methodology.

Quad-Band Rectenna for RF Energy Harvesting System

The design of multiband microstrip rectenna for radio frequency energy harvesting applications is presented in this paper. The designed antenna has good performance in the GSM-900/1800, WiFi and WLAN bands. In addition, the rectifier circuit is designed at multi resonant frequencies to collect the largest amount of RF ambient power from different RF sources. The developed antenna is matched with the rectifier at four desired frequencies using several rectifier branches to collect the largest of RF power. The proposed rectenna is printed on FR4 substrate with modified ground plane to achieve suitable impedance bandwidth. The proposed antenna consists of elliptical radiating plane with stubs and stepped modified ground plane. The rectenna resonates at quad frequency bands at (GSM 900/1800, WiFi band and WLAN bands) with rectifier power conversion efficiency up to 56.4% at 0 dBm input power using the HSMS-2850 Schottky diode. The efficiency is more enhanced by using SMS-7630-061 Schottky diode which is characterized by a low junction capacitance and a low threshold voltage to achieve higher conversion efficiency up to 71.1% at the same 0 dBm input power for the same resonating frequency band.

Enslavement of Wireless Sensor Network to an RF Energy Harvesting System

The abundance of telecommunications systems makes it possible to have somewhat significant quantity of radiofrequency energy in the environment. This energy can be recycled to power ultra-low-power devices such as Wireless Sensor Network (WSN). In this paper, the performance of a miniature RF/DC converter is evaluated in order to enslave a WSN’s per-formance to the amount of the recovered energy. More precisely, a highly sensitive and efficient rectifier is designed to achieve optimum performance in the GSM band. The design method relies on a judicious choice of the rectifying diode which is the basis of most losses in a rectifying antenna (rectenna). Optimum performance is achieved by using the gradient method search proposed in the Advanced Design System (ADS) software. A rectifier based on Schottky diodes HSMS 2850 used in a voltage doubler topology is thus obtained. A maximum RF/DC conversion efficiency of 36% is reached for an RF input power level of 10 dBm. An energy budget of a sensor node in a WSN having an equitable distribution of network loads is then defined and used to evaluate the performance of the WSN regarding the distance at which the Base Station (BS) can be located. The Low Energy Adaptive Clustering Hierarchy (LEACH) protocol is used for this purpose. The distance separating the WSN from the BS is used as the enslavement parameter. Our analysis shows that increasing the duration of each round results in an increase in the range of the WSN. As an example, a network with 100 nodes distributed over an area of may be located at 1.3 km from the base station when each node of the WSN must perform measurements every 1 min.

Design of a Rectenna in 2.45 GHz Band Frequency for Energy Harvesting

There are several sources of energy recovery in the ambient environment. The radiofrequency energy harvesting system is used to harvest the electromagnetic energy in the air by processing energy sources to charge low-power electronic devices. Rectenna termed as a rectifying antenna is a device that is used to convert electromagnetic waves in the air into direct electric current. In this work, we have designed firstly the patch antenna with a small size printed on the FR4 substrate (40 mm × 47.5 mm × 1.6 mm) and then the rectifier circuit. This rectenna is capable of working at a frequency range of 2.45 GHz. The antenna was designed using High Frequency Structure Simulator (HFSS) 13.0 software with the result of working frequency of 2.453 GHz, S11 (Return Loss) -52 dB, Voltage Standing Wave Ratio (VSWR) 1.036, gain 3.48 dB and bandwidth 150 MHz. The efficiency of rectifier design on Advanced Design System (ADS) 2011 software is 54% at the input power of 0 dBm at 2.45 GHz. The resulting system is capable of producing electrical energy to power low-power electronic equipment at a DC voltage of 732 mV.

Designing Wireless Charger Circuit for Hearing Aids Using Radio Frequency Waves

In this paper, an attempt has been made to produce a recipient system of wireless charge for a simple hearing aid so that electrical signal would be generated through detecting and receiving radio frequency waves (RF). The purpose of this design is to receive wireless charge for hearing aids and basically for any electronic device which is not required to a high energy for being setup. In this study, it has been demonstrated that as the amount of radio receiving energy increases, distance of receiver from antenna should be decreased;otherwise, either maximum amount of the receiving energy, or signal power density of the transmitter should be increased. Since it is impossible to be performed, it is decided to set up an energy receiving system constructed by rectenna and charge Circuit and to adjust their parameters to provide energy requirements for a device with low-power consumption. In this paper, different components of an energy receiving system from radio frequency band have been mentioned and a diagram block has been suggested. Subsequently, input impedance of designed antenna has been adjusted by provided relations. This impedance should be adjusted with the total impedance of regarded hearing aid Circuit by which the highest amount of received signal power is transferred to the battery of hearing aids. Received signal is converted to a dc voltage by rectifier diode. Finally, by applying a voltage regulator which has been designed using a common-collector amplifier not only the output voltage is kept constant, but the power is also strengthened. The battery of the hearing aids will be charged using the obtained power and voltage.

Wireless Energy Harvesting Using Rectenna Integrated with Voltage Multiplier Circuit at 2.4 GHz Operating Frequency

In this paper, we utilized villared rectifier technique to harvest wireless energy to overcome previously used RF-WEH rectenna. Our design focuses mainly on a multiple-stage Villard voltage multiplier model to rectify the output voltage of the rectenna and transferred it to a dc load. As a starting point, optimization and parameter analysis offer a novel and small antenna for the 2.45 GHz ISM band that precisely matched. Moreover, the fabricated prototype has measured and simulated results have confirmed the antenna’s accuracy in the reflection coefficient. Second, a highly efficient antenna may effectively harvest the electrical energy by combining with the two-stage voltage multiplier circuit presented at the ISM band. Furthermore, the proposed rectenna has the optimum performance compared to state of art rectennas in terms of efficiency, power range, and impedance bandwidth showing pronounced achievement and increasing the DC output power significantly. The prototype is fabricated and experimentally tested to confirm the concept. Measurement results show that the proposed rectenna can be used for RF energy harvesting applications.

Terrestrial transparent green energy receiving system designed for Space Solar Power Station

In this manuscript,we proposed the concept of a terrestrial transparent energy receiving system for a Space Solar Power Station(SSPS),aiming at solving the problems of environmental destruction and the waste of land resources caused by the construction of large area rectenna arrays at the traditional terrestrial receiving system.We also fabricated a demonstration model of the new system.The system’s energy receiving and converting device consists of many rectenna arrays that are flexible,transparent,and matching network eliminated to harvest the microwave energy averaging about 80 mW/m^(2) on the ground from the Solar Power Satellite(SPS).The rectenna unit of the system operates at 2.45 GHz,and the measured RF to DC conversion efficiency reaches 20%at−10 dBm and up to 64.65%at 6.8 dBm.As the rectenna array of the system has the advantages of both microwave energy harvesting and light transmittance,conventional solar panels can be placed underneath to collect sunlight and convert it into electricity.It is also feasible to build“self-powered”smart agricultural greenhouses for vegetable cultivation underneath so that the collected energy can be utilized locally to avoid the waste caused by long-distance transmission.The proposed system is of great significance to the research on environmental protection and efficient utilization of land resources at the terrestrial energy receiving system of the Space Solar Power Station.

High gain multiband planar spiral slot rectenna with dipole arms

A novel low profile multiband rectenna was proposed for harvesting the 2 nd generation(2 G), the 3 rd generation(3 G), the 4 th generation(4 G), wireless local area networks(WLANs) etc., electromagnetic wave energy. The proposed rectenna consists of a novel multiband antenna and a rectifier. The multiband antenna includes a radiating element on one side of a single layer dielectric substrate and a feeding spiral balun on the other side of the substrate. A conductive via is connected between the balun and the radiating element. In the radiating element, a deformed dipole structure is connected with an equiangular spiral slot structure and is used to generate a low frequency radiation around 900 MHz. The multiband antenna can work simultaneously at 0.869 GHz^0.948 GHz, 1.432 GHz^2.173 GHz, and 2.273 GHz^2.465 GHz with its peak gains of 7.1 dBi at 903 MHz, 4.1 dBi at 1 800 MHz, 5.2 dBi at 2 430 MHz. The radio frequency to direct current(RF-to-DC) conversion efficiencies of the rectifier are 58%~62% at these three frequencies for an input power of 0 dBm. The overall measurement results validate that the rectenna suits for energy harvesting and exhibits approximate maximum efficiencies of 58% at 0.9 GHz, 56% at 1.8 GHz, and 55% at 2.4 GHz with a low incident power density of 8 μW/cm^2.

A review of self-assembled monolayers as potential terahertz frequency tunnel diodes

In this review, we describe the principles of the tunnel junction, self-assembled monolayer （SAM） application techniques, experimental testbed fabrication, and characterization of the films and devices. In addition, techniques for directed application, removal, and functionalization of the monolayers are discussed. Bottom-up fabrication techniques have seen increased attention because of their versatility and ease of use. These films see mechanical uses as surface modifiers and micro-scale lubricants. Advances in nanowatt electronics and ultra-low power sensors have opened up an energy harvesting niche for solutions which would have proven ineffective just some years ago. The focus of this study is the two- terminal junction which has potential applications in THz rectification for energy harvesting, medical imaging, and defense sensing. The quantum theory of operation behind these devices is touched on briefly---describing tunneling through the organic monolayers. Commentary on trends in research and potential future work are presented as well.