A dual‐band efficient circularly polarized rectenna for RF energy harvesting systems

A multilayered circularly polarized (CP), dual‐band, stacked slit‐/slotted‐patch antenna with compact size and with compact rectifier is offered for RF energy harvesting systems. The compact dual‐band CP antenna size is able to achieve by stacking slotted‐circular‐patch (SCP) on the substrate above the tapered‐slit‐octagon patch (TSOP). Dual‐band CP radiation is realized by stacking the SCP on the TSOP and the microstrip feedline with metallic‐via to SCP. Eight‐tapered‐slit with length difference of 6.25% are embedded along the octagonal directions symmetrically on the TSOP from the patch's center and two unequal size circular slots are embedded in diagonal axis onto SCP to produce dual‐orthogonal modes with almost equal magnitude for CP waves. The designed antenna is realized measured gain of greater than 5.2 dBic across the band (0.908‐0.922 GHz) with maximum gain of 5.41 dBic at 0.918 GHz and gain of greater than 6.14 dBic across the band (2.35‐2.50 GHz) with maximum gain of 7.94 dBic at 2.485 GHz. An overall antenna volume is 0.36λ _o × 0.36λ _o × 0.026λ _o (λ _o is free space wavelength at 0.9 GHz). A compact composite right‐/left‐handed (CRLH) based rectifier with dual‐band at 0.9 and 2.45 GHz is designed, prototyped, and measured. The right‐handed (RH) part of the CRLH transmission line (TL) is formed by a microstrip line. The left‐handed (LH) part of the CRLH‐TL is formed by lumped components. The measured RF‐DC conversion efficiency is 43% at 0.9 GHz and 39% at 2.45 GHz with rectifier size of 0.18λ _o × 0.075λ _o × 0.0002λ _o at 0.9 GHz.     

Design and realization of an ultra‐low power sensing RF energy harvesting module with its RF and DC sub‐components

Herein, design, development, and analysis of ultra‐low power sensing energy harvesting modules and their subcomponents for ISM band applications have been studied with a holistic approach in an effort to achieve a feasible and high efficient RF energy harvesting performance. The complete harvester system designed and developed here consists of a zero‐bias RF energy rectifying antenna (rectenna), DC boost converters and energy storage super‐capacitors. Compared with the counterpart energy sources, the surrounding or transmitted wireless energy has low intensity which requires designs with high efficiency. To achieve a successful harvester performance, rectifier circuits with high sensitivity Schottky diodes and proper impedance matching circuits are designed. Dedicated RF signals at various levels from nanowatts to miliwatts are applied at the input of the rectenna and the measured input power versus the scavenged DC output voltage are tabulated. Furthermore, by connecting the rectifier to a high gain antenna and using a RF signal transmitter, the wireless RF power harvesting performance at 2.4 GHz was tested up to 5 m. The performance of the rectenna is analyzed for both low‐power detection and efficiencies. Impedance matching network is implemented to reduce the reflected input RF power, DC to DC converters are evaluated for their compatibility to the rectifiers, and super‐capacitor behaviors are investigated for their charging and storage capabilities. The measured results indicate that a wide operating power range with an ultra‐low power sensing and conversion performance have been achieved by optimizing the efficiency of the Schottky rectifier as low as ?50 dBm. The system can be used for battery free applications or expanding battery life for ultra‐low power electronics, such as; RFID, LoRa, Bluetooth, ZigBee, and low power remote sensor systems.     

一种共面带状线高增益整流天线的设计

为了解决微小型机器人应用过程中能量供应的问题,介绍了一种应用于微小型机器人,由共面带状线组成的阶跃阻抗滤波器整流天线设计方法,这种整流天线具有结构简单、不需要集总元件即可滤波、能够对系统进行电磁场仿真、制作方便等优点。同时,在振子天线后面加上反射器,提高了天线增益。利用ADS2005A的Momentum对整流天线进行了仿真及实验验证,证明了设计的可行性。     

Dependence of dc output of a rectenna array on the method of interconnection of its array elements

In 1994 and 1995, a ground-to-ground microwave power transmission (MPT) experiment was carried out by a group including participants from Kyoto University, Kobe University, and Kansai Electric Power Company. Among the MPT technologies, which are one of the most important key issues for the realization of the Solar Power Satellite, the “rectenna” (rectifying antenna) has been studied to achieve higher efficiency of conversion from microwave to dc We had developed a new rectenna panel which can effectively rectify a microwave power of 2.5 W at 2.45 GHz, prior to the ground-to-ground MPT field experiment. We examine the sum of the outputs of two or three rectenna panels which are connected either in parallel or in series or in a hybrid manner under the same microwave circumstances. The experiments lead us to conclude: (1) The sum of the dc outputs from two rectenna panels connected in parallel is larger than that from those connected in series. (2) The sum of the dc outputs of two rectenna panels is generally smaller than the sum of the dc output of the individual panels unless their outputs are equal. (3) Better total output dc power of a rectenna array is achieved when we take careful account of the array element balance. Based on the experiments, we propose an optimum method for connection of individual rectenna elements to form a high-efficiency rectenna array. © 1998 Scripta Technica, Electr Eng Jpn, 125(1): 9–17, 1998     

整流天线技术及应用

整流天线能把空间的微波能量转化为直流能量。本文分析了它的工作原理,介绍了几种理论分析方法和关键指标测试方法,并进一步分析研究了检波二极管微波/直流转换效率随负载和输入功率的变化关系。最后,列举了整流天线技术在工程技术领域已取得的成果并分析了它的应用前景。     

一种2.45 GHz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2.45 GHz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20 dBm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.     

无线传感器网络中的整流天线技术研究进展

本文介绍了适用于无线传感器网络的、能进行无线输能的整流天线和能进行无线定位的时间反演算法.适用于无线传感器网络的整流天线要求紧凑的天线结构,高效的微波能量到直流电量的转换效率以及较高的入射波频率.利用时间反演算法的时-空聚焦特性,可解决无线传感器网络中节点无线定位问题,以提高整流天线的效率.     

A novel meander line integrated E‐shaped rectenna for energy harvesting applications

In this article, design of a novel meander integrated E‐shaped rectenna is presented. The designed rectenna operates at ISM frequency range from 2.2 to 2.5 GHz with acceptable reflection coefficients, gain and VSWR values. The designed rectenna is simulated using HFSS 15 (High Frequency Electromagnetic Field Simulation) and FR4 epoxy material is used in rectenna design for low cost having dielectric constant of 4.4 and thickness of 1.6 mm. In the rectifying stage full wave voltage doubler circuit is designed for DC power generation with SMS7630 Schottky diode and lumped circuit elements. The impedance matching circuit between the antenna and the rectifier is designed and simulated using advanced design system (ADS) software for efficient power transmission from the antenna to the load. The simulation and measurement results with different load and input power levels prove that the designed and implemented system can be used for low power energy harvesting applications in order to feed electronic components and battery free sensor networks.     

An ultra‐wideband rectenna using optically transparent Vivaldi antenna for radio frequency energy harvesting

This paper presents a novel ultra‐wideband rectenna which consists of a transparent Vivaldi antenna and a wideband rectifying circuit for radio frequency energy harvesting. The antenna is realized on a 2.2‐mm‐thick soda‐lime glass substrate coated with fluorine‐doped tin oxide of thickness 650 nm. It provides an optical transmittance greater than 80% in the visible region. The rectifying circuit with a cascaded matching network and the Greinacher doubler circuit are fabricated on an FR4 substrate with a thickness of 0.8 mm. The antenna provides the best matching characteristics and the realized peak gain is 3.2 dBi. The designed matching network enables maximum power transfer from the antenna to the rectifier. The rectenna provides a peak power conversion efficiency of 69% for ?10 dBm input power. The proposed antenna can be realized on the windscreen of automobiles and glass windows without causing any obstruction to normal view.     

新型CPS型低通滤波器在整流天线中的应用

提出了一种新型共面带状线(CPS)低通滤波器,并将其用于圆极化整流天线中。该滤波器实现了小插损、宽阻带。通过宽带巴伦转换,实验测得衰减大于15dB的阻带带宽达到10.3GHz,5.8GHz处插入损耗为1.62dB,在11.6GHz和17.4GHz处插入损耗分别为30.3dB和26.3dB,与仿真结果吻合较好,有效地抑制了二次和三次谐波。将该低通滤波器应用于圆极化整流天线中,测得高达72.3%的RF-DC(Radio Frequency-Direct Current)转换效率,该整流天线可作为无线输能系统的接收部件。