Optimization of the Voltage Doubler Stages in an RF-DC Convertor Module for 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 5.0 V in measurement. This voltage can be used to power low power sensors in sensor networks ultimately in place of batteries.

RF energy harvesting system for wireless intraocular pressure monitoring

This paper presents an RF energy harvesting system for wireless intraocular pressure monitoring applications.The system consists of an implantable antenna and a rectifier.A new sizing strategy is adopted to optimize the conversion efficiency of the rectifier,and the design principle of an implantable antenna is introduced from material selection and structure design.Results from testing demonstrate that the antenna gain is about-20 dBi and the rectifier's maximum total conversion efficiency which contains match efficiency and rectifying efficiency is 47.18%under the implementation of0.18μm standard CMOS process.The maximum power obtained from the proposed system is 8μW when the power density of electromagnetic wave is lower than the national standard 40μW/cm^2 at915 MHz,which is enough to power the intraocular pressure monitoring system.

Design of a Five-Band Dual-Port Rectenna for RF Energy Harvesting

This paper proposed the design of a dual-port rectifier with multifrequency operations.The RF rectifier is achieved using a combination of L-section inductive impedance matching network(IMN)at Port-1 with a multiple stubs impedance transformer at Port-2.The fabricated prototype can harvest RF signal from GSM/900,GSM/1800,UMTS/2100,Wi-Fi/2.45 and LTE/2600 frequency bands at(0.94,1.80,2.10,2.46,and 2.63 GHz),respectively.The rectifier occupies a small portion of a PCB board at 0.20λg×0.15λg.The proposed circuit realized a measured peak RF-to-dc(radio frequency direct current)power conversion efficiency(PCE)of(21%,22.76%,25.33%,21.57%,and 22.14%)for an input power of−20 dBm.The RF harvester attains a measured peak RF-to-dc PCE of 72.70%and an output dc voltage of 154 mV for an input power of 3 dBm at 2.46 GHz.Measurement of the proposed rectifier in the ambiance gives a peak dc output voltage of 376.1 mV from the five signal tones.Similarly,a low-powered bq25504-674 evaluation module(EVM)is integrated with the rectifier.The module boost and drive the rectifier output dc voltage to 945 mV.The performance of the proposed rectifier in the ambiance environment makes it a suitable module for low-powered RF 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.

A Compact Dual-Port Multi-Band Rectifier Circuit for RF Energy Harvesting

This paper presents a compact multi-band rectifier with an improved impedance matching bandwidth.It uses a combination of–matching network(MN)at Port-1,with a parallel connection of three cell branch MN at Port-2.The proposed impedance matching network(IMN)is adopted to reduce circuit complexity,to improve circuit performance,and power conversion efficiency(PCE)of the rectifier at low input power.The fabricated rectifier prototype operates at 0.92,1.82,2.1,2.46 and 2.65 GHz covering GSM/900,GSM/1800,UMTS2100,and Wi-Fi/2.45–LTE2600.The size of the compact rectifier on the PCB board is 0.13λ_(g)×0.1λ_(g).The fabricated rectifier achieved an RF-to DC(radio frequency direct current)PCE of 31.8%,24%,22.7%,and 15%,and 14.1%for−20 dBm at the five respective measured operating frequencies.The circuit attains a peak RF-to-DC PCE of 82.3%for an input power of 3 dBm at 0.92 GHz.The proposed rectifier realizes an ambient output dc voltage of 454 mV for multi-tone input signals from the two ports.The rectifier drives a bq25504-674 power management module(PMM)to achieve 1.21 V from the two-port connection.The rectifier has the ability to exploit both frequency domain through the multi-band operation with good impedance bandwidth and a spatial domain using dual-port configuration.Hence,it is a potential candidate for various applications in radio frequency energy harvesting(RFEH)system.

Cross Layered MAC Design for RF Energy Harvesting Sensor Network

The main research objective in wireless sensor networks (WSN) domain is to develop algorithms and protocols to ensure minimal energy consumption with maximum network lifetime. In this paper, we propose a novel design for energy harvesting sensor node and cross-layered MAC protocol using three adjacent layers (Physical, MAC and Network) to economize energy for WSN. The basic idea behind our protocol is to re-energize the neighboring nodes using the radio frequency (RF) energy transmitted by the active nodes. This can be achieved by designing new energy harvesting sensor node and redesigning the MAC protocol. The results show that the proposed cross layer CL_EHSN improves the life time of the WSN by 40%.

Effect of oxygen partial pressure and transparent substrates on the structural and optical properties of ZnO thin films and their performance in energy harvesters

Zinc oxide(ZnO) thin films were deposited onto different substrates — tin-doped indium oxide(ITO)/glass, ITO/polyethylene naphthalate(PEN), ITO/polyethylene terephthalate(PET) — by the radio-frequency(RF) magnetron sputtering method. The effect of various O2/(Ar+O2) gas flow ratios(0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) was studied in detail. ZnO layers deposited onto ITO/PEN and ITO/PET substrates exhibited a stronger c-axis preferred orientation along the(0002) direction compared to ZnO deposited onto ITO/glass. The transmittance spectra of ZnO films showed that the maximum transmittances of ZnO films deposited onto ITO/glass, ITO/PEN, and ITO/PET substrates were 89.2%, 65.0%, and 77.8%, respectively. Scanning electron microscopy(SEM) images of the film surfaces indicated that the grain was uniform. The cross-sectional SEM images showed that the ZnO films were columnar structures whose c-axis was perpendicular to the film surface. The test results for a fabricated ZnO thin film based energy harvester showed that its output voltage increased with increasing acceleration of external vibration.

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.

Energy Harvesting——Technical Analysis of Evolution,Control Strategies,and Future Aspects

This paper provides a technical analysis of energy harvesting (EH) in the field of power and energy sector, including different aspects of harvesting energy, individual case history, control strategies of harvesting in the field of power and energy sector together with the current trend and future aspects of it. EH is comparatively a new concept which is growing very fast since the 20th century and catching new generation research approaches. This paper not only describes the past and current scenarios of harvesting energy with radio frequency (RF) and renewables but also gives author’s own anticipation of the upcoming future trends of it by comparing the case histories.

Ultra-Low Power High-Efficiency UHF-Band Wireless Energy Harvesting Circuit Design and Experiment

In this paper,an ultra-low power high-efficiency ultra-high frequency(UHF)-band wireless energy harvesting circuit based on the diode SMS7360 is designed and experimentally demonstrated,being operated in all released Global System for Mobile Communications(GSM)bands in China(GSM900 band:0.87-0.96 GHz and GSM1800 band:1.71-1.86 GHz).This UHF-band wireless energy harvesting circuit can harvest energy at 0.87-0.96 GHz and 1.71-1.86 GHz bands simultaneously in outdoor or indoor environment.The test results show that a radio-frequency(RF)-to-direct-current(DC)conversion efficiency in the range of 20%-63.2% is obtained for an available input power of-22 dBm to 1 dBm in GSM900 band and that in the range of 13.8%-55.5% is achieved for an available input power of-22 dBm to 3 dBm in GSM1800 band.The harvested RF energy is converted into DC energy and be stored in a 6.8 mF super capacitor through the energy management circuit.This super capacitor’s capacity is more than 20 mJ,which can meet the demand of high-speed broadband wireless communication transceivers.This ultra-low power highefficiency UHF-band wireless energy harvesting circuit could be used to achieve the low power wireless sensor network node(tag).

Design of Wireless Energy-Harvested UHF WSN Tag for Cellular IoT

In this paper,a wireless energy-harvested ultra-high frequency(UHF)wireless sensor network(WSN)tag is designed and implemented for cellular Io T applications.The WSN tag is made up of a wireless energy harvesting circuit,a temperature sensing circuit,and a radio frequency identification(RFID)tag.The developed WSN tag is compatible with the ISO/IEC18000-6C protocol.The WSN tag can receive the GSM RF energy operating in China GSM900 and GSM1800 bands in the surrounding environment and the solar energy,then converts the RF energy to direct current(DC)by schottky diode-based rectifying circuit,and finally stores the DC energy in a supercapacitor through a DC-DC booster circuit.The DC-DC booster circuit drives the front-end circuit,TI MSP430 microcontroller,temperature sensing circuit,and other active circuits in the tag.The MSP430 works in low-power mode when it is powered up,and it can also reduce power consumption more by reducing main clock(MCLK)frequency according to different forward link rates.The implemented WSN tag demonstrated that the RF-to-DC conversion efficiency is higher than 39% when the receiving 900 MHz RF signal power is from -14 dBm to 0 dBm and could make the tag work normally.The signal receiving sensitivity of the WSN tag is up to-32 dBm at the rate of 40 kbit/s from the Reader to the WSN tag.The WSN tag supports Miller coding and extended Miller coding.This wireless energy harvested UHF WSN tag,compared with conventional UHF passive tags and battery-powered active UHF RFID Tags,has many advantages,such as far communication distance,long service life,and sensing functionality.It will have wide applications in the Internet of Things(IoT).

用于射频能量收集的低阈值CMOS整流电路设计

基于TSMC 180 nm工艺,设计了一款高效率低阈值整流电路。在传统差分输入交叉耦合整流电路的基础上,提出源极与衬底之间增加双PMOS对称辅助晶体管配合缓冲电容的改进结构,对整流晶体管进行阈值补偿。有效缓解了MOS管的衬底偏置效应,降低了整流电路的开启阈值电压,针对较低输入信号功率,提高了整流电路的功率转换效率(PCE)。同时将低阈值整流电路三级级联以提高输出电压。测试结果显示,在输入信号功率为-14 dBm@915 MHz时,三级级联低阈值整流电路实现了升压功能,能稳定输出1.2 V电压,峰值PCE约为71.32%。相较于传统结构,该低阈值整流电路更适合用于射频能量收集。

用于微波无线输能的高增益柔性天线研究

为克服传统有线供能方式的接入不便问题,提出了一种用于5.8 GHz微波无线输能(MWPT)高增益柔性天线。天线以聚酰亚胺(PI)为基底,采用广义迭代设计方法得到3层圆环结构,并选用共面波导(CPW)方式馈电。此外,为提高天线增益,在天线背面加载空气层和柔性反射板,并对天线性能进行了测试。测量结果显示:该天线在频率5.8 GHz处的峰值增益为9.51 dBi;当天线弯曲在曲率半径为85,60,45 mm时,增益始终保持在8.89 dBi以上,S_(11)幅值始终小于-10 dB。最后,通过微波无线输能实验测得该天线最大能量捕获效率可达71.3%,在弯曲状态下也能保持59%以上的捕获效率。该天线的高增益、高能量捕获效率以及稳定性证明了其在微波无线输能中具有潜在的应用价值。

以纺织微带单元及阵列天线为接收天线的射频能量收集系统输出电压比较研究

近些年,纺织天线作为可穿戴产品射频能量收集系统中的重要电子设备,越来越受到青睐。为研究基于纺织天线的射频能量收集系统的收集性能,该研究设计并制备了以涤纶毡为基底的纺织微带单元天线和纺织微带阵列天线。为了建立一个完整的射频能量收集系统,将信号发生器、功率放大器、发射天线和所设计的纺织微带天线(作为接收天线)与整流电路连接。研究结果表明,阵列天线的最大增益比单元天线高5.35 dB。最终的输出电压显示了射频能量收集系统的有效性。随着输入功率的增加、接收距离的减小,输出电压增加。通过单元天线的最高输出电压为39.2 mV,通过阵列天线的最高输出电压为72.7 mV,这是由于阵列天线的增益较高。这项研究将为该领域带来更多的研究思路。

基于射频能量收集的无线中继网络资源分配

针对现有射频能量收集网络资源分配研究局限于单个数据源场景,无法适配于多数据源网络的问题,提出了一种适用于多数据源场景的射频能量收集中继网络传输协议框架,在该框架内节点可作为源节点或中继节点传输自身数据或转发数据,并在其他节点的数据传输过程中完成射频能量收集。以协议框架为基础,分别以系统吞吐量及用户公平性为优化目标设计两种资源分配方案。仿真表明,两种方案可有效改善网络吞吐量及资源分配公平性。

基于微波无线能量传输多径效应的多角度超表面能量收集器

文中深入研究了基于微波无线能量传输技术的多径效应及其对多角度超表面能量收集器的性能的影响。首先,概述了微波无线能量传输技术的基本原理与发展现状,随后详细讨论了超表面结构在多角度能量接收中的应用。通过理论分析与仿真实验,文中提出了一种优化的超表面设计方案,以提高能量收集效率。实验结果显示,该方案能显著提高多角度超表面能量收集器在复杂传播环境下的能量收集性能,不仅为超表面能量收集器的设计提供了新的视角,也为未来无线能量传输技术的发展提供了理论参考。

具有能量收集的双向RF/FSO中继系统性能分析

设计了一种在大气湍流和指向误差影响下的带有能量收集的混合双向RF/FSO中继传输系统。RF信号部分采用能量分割的方式进行能量收集,FSO信号部分则将其信号中的直流电分量所携带的能量收集起来存储在中继器中。其中射频RF链路采用Nakagamim信道衰落模型,自由空间光FSO链路采用Gamma Gamma信道衰落模型。并且计算出了两条链路各自的累积分布函数CDF。采用DF的中继协作方式,并利用Meijei G函数推导出系统中断概率的闭合表达式,最终通过仿真来验证结果的正确性。

RF能量采集全双工认知无线网络中协作频谱感知参数优化

在RF能量采集全双工认知无线网络中,次级用户同时进行频谱感知、数据传输和能量采集,提高了能效和谱效。将次级网络的能效定义为平均吞吐量与平均消耗功率之比,将采集效率定义为平均采集能量与平均消耗能量之比。将协作频谱感知引入RF能量采集全双工认知无线网络中,以提高次级用户的感知性能,进而提高能效和采集效率。协作频谱感知的感知性能与融合准则密切相关,因此考虑采用k-out-of-N融合准则,并提出优化融合准则参数k值的算法,经过仿真得到使能效和采集效率最优的k值。

CMOS衬底调制阈值调整型RF-DC整流器

基于CMOS交叉耦合桥式射频整流器结构,在MOS整流管的栅极与衬底之间引入耦合电容,利用衬底调制效应动态调整MOS整流管的阈值电压,从而提高射频整流器的输出电压,减小稳定时间。对整流器工作原理进行了分析,对电路进行了仿真。结果表明,改进后的CMOS交叉耦合桥式整流器在输入功率为-16dBm@900 MHz时,输出电压为1.48V,输出电压和稳定时间分别比传统电路提高了13mV和22μs。

移动通信信号对射频能量采集系统中RF-DC整流电路的影响分析

随着无线技术的飞速发展,无线技术传递信息的同时也可以进行能量的传递。空间环境中遍布各种无线信号,特别是移动通信信号,这些信号能量的收集技术已成为科学研究领域的研究热点。随着传感器等微型化、低功耗电子器件的普及,从周围环境中收集能量为其供电已成为可能。因此,首先介绍射频能量收集系统的各部分组成,分析系统中能量转化效率;其次,介绍射频整流电路;最后,分析移动通信中2G和3G信号,分别是GSM信号、WCDMA信号和CDMA2000信号的特点,以及正弦信号对系统能量转化效率的影响。