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.

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.

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.

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.

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.

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.

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.

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.

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.

Design of a sector bowtie nano-rectenna for optical power and infrared detection

We designed a sector bowtie nanoantenna integrated with a rectifier （Au-TiOx-Ti diode） for collect- ing infrared energy. The optical performance of the metallic bowtie nanoantenna was numerically investigated at infrared frequencies （5-30 μm） using three-dimensional frequency-domain electro- magnetic field calculation software based on the finite element method. The simulation results indi- cate that the resonance wavelength and local field enhancement are greatly affected by the shape and size of the bowtie nanoantenna, as well as the relative permittivity and conductivity of the dielectric layer. The output current of the rectified nano-rectenna is substantially at nanoampere magnitude with an electric field intensity of 1 V/m. Moreover, the power conversion efficiency for devices with three different substrates illustrates that a substrate with a larger refractive index yields a higher efficiency and longer infrared response wavelength. Consequently, the optimized structure can pro- vide theoretical support for the design of novel optical rectennas and fabrication of optoelectronic devices.

一种紧凑型高效率毫米波整流天线

为了提高毫米波无线输能系统的接收端效率,设计了一款基于缝隙耦合馈电的紧凑型高效率毫米波整流天线,该整流天线通过划分子阵,每个子阵单独进行能量转换,采用直流合成的方式进行整合输出,具有尺寸小、剖面低、易共形等特点。天线采用缝隙耦合馈电,馈线和辐射贴片分别在地板的两侧,有效的减少天线电路之间的影响,同时增大了天线的有效辐射面积。后端整流电路采用单二极管并联整流拓扑,利用扇形枝节作为直通滤波器进行直流滤波。该整流天线工作频率为35GHz,天线阵列增益为23.4dBi,实测在17dBm接收功率下具有最高58.65%的整流效率,可广泛应用于毫米波无线输能系统中。

无线能量传输整流天线技术研究进展

近年来,无线电技术不断发展,其中无线能量传输技术可以实现无线供电,引起了广泛关注,具有很高的研究价值和应用前景。无线能量传输系统中的整流天线用来将接收到的电磁波转换为直流电,其转换效率是衡量系统能量传输能力的一个重要指标。文中首先介绍了无线能量传输技术的基本原理,接下来阐述了无线能量传输整流天线的研究进展,总结了近年来整流天线设计的主流技术方案,包括多频段和宽带整流天线、谐波抑制整流天线、高增益整流天线、双极化整流天线、大功率及负载范围整流天线、基于电磁超材料的整流天线等,并讨论了不同方案的关键技术及优势,展望了未来的发展趋势。

空间太阳能电站微波能量传输验证方案设计

微波能量传输技术作为空间太阳能电站(Space Solar Power Station,SSPS)的关键技术之一,目前的研究和验证工作均集中在各单项技术的突破和验证,缺乏针对SSPS系统特点的全面优化设计。文章根据SSPS的工作模式给出了全面验证空间太阳能电站微波能量传输的验证系统方案设计,对收发天线进行了一体化设计,利用了幅度近似高斯分布的发射阵列场分布设计和低反射的接收整流阵列设计,以高精度来波方向测量和高精度移相控制为波束指向控制的技术途径。对验证系统的波束收集效率进行了分析,收集效率可达94.2%,比传统均匀分布系统高出17.6%。验证系统可从系统规模缩比、波束扫描范围、发射天线口径场分布、整流天线处功率密度、反向波束控制方法等方面模拟SSPS微波能量传输工作模式,推动SSPS系统技术的发展。

微波无线输能技术研究进展与系统设计

微波无线输能(microwave wireless power transmission,MPT)技术应用于不易获取直流电能的场合,是研制太阳能卫星、近空间飞行器的关键技术,也可应用于无线传感器网络节点供能及环境低微微波能量的回收.比较了微带线型和共面带状线型2种典型整流天线的单元和阵列性能,提出了对接收天线和整流电路的要求;以获得最大微波波束捕获效率为目标,分析了发射天线拓扑结构及高斯削尖口径电平分布.在研究以上关键技术的基础上设计了一套C波段微波输能系统,该系统从发射端到接收端的直流-直流效率为35%.最后指出了微波无线输能技术存在的问题和未来发展方向.

整流天线组阵等效模型分析与实验

将整流天线单元等效为一个直流源和负载的串联,以此提出了整流天线串/并联组阵等效模型,得到了整流天线的组阵形式及最佳负载与阵元个数之间的关系.利用所设计的低功率密度应用整流天线单元,通过ADS软件仿真了二元并联阵,并通过实验测试了二元串联阵与二元并联阵.结果显示,并联阵的仿真与实验结果及串联阵的实验结果均与组阵模型基本吻合,从而验证了整流天线组阵模型的有效性.提出了多元组阵的可行性方案,为大规模阵列设计提供指导.

肖特基二极管整流的计算与测量

提出了改进型的肖特基二极管整流数理模型,用加速迭代法和四阶精度龙格-库塔法编制了计算程序,并结合实验测量得到了整流效率与输入功率、频率和负载等关系曲线:负载一定时,输入功率从零开始增大,整流效率先快速上升,然后上升趋势变缓;输入功率一定时,负载从零开始增大,整流效率先增大后减小,对于某一固定的输入功率,存在着一个最佳负载值;当输入功率和负载都相同时,降低工作频率,整流效率上升。型号为2DV10B的X波段管子在负载为525Ω、输入功率为10 mW、频率为3.2 GHz时获得的整流效率为75.2%;频率为10 GHz时获得50.2%的效率,实验测量结果与理论分析一致。

一种2.45GHz微波二极管整流电路

为了提高用于微波无线功率传输的微波整流效率,本文采用微带结构实现了一个2.45GHz的微波二极管整流电路。仿真实验结果证明在输入功率约为20dBm的情况下,获得了大于50%的整流效率。通过完善和改进电路,可以进一步提高整流的效率,并应用于微波整流天线。

一种实用线极化矩形微带贴片接收整流天线的仿真设计

太空电站以及微波输电被认为是解决人类能源危机的一个切实可行的方案之一 ,本文介绍了微波接收整流天线的原理 ,设计了一种实用、尺寸简洁的线极化矩形微带贴片接收和整流天线 ,通过高频电磁仿真软件An softDesignerV1.0仿真表明该系统中二极管的转换效率超过 70 % ,系统总转换效率大于 63 % ,验证了该设计在理论和实际上的可行性。

多界面匹配高效微波整流天线设计方法

整流天线效率对远距离微波能量传输的整体效率至关重要.针对传输系统接收整流端效率提升的需求,提出了一种多界面匹配高效微波整流天线的设计方法.首先对整流天线的效率给出了数学描述,并据此在能量波束入射界面、能量转移界面、能量转换界面、直流合成界面提出了匹配原理和方法.多界面匹配联合就形成了高效整流天线设计方法.最后,根据相关匹配原理进行了实验验证,证实了对波阻抗匹配和输入阻抗匹配的分析.