一款2.4GHz～2.5GHz的RF能量收集系统设计

近年来,为了达到控制环境的目的,无线传感器网络迅速兴起,但传感器节点的生命周期对电池容量有很大的依赖性。为解决无线传感器不可持续性供电的问题,设计一款收集环境频率在2.4GHz～2.5GHz的能量采集系统,主要由微带天线、阻抗匹配电路、四倍压整流电路组成。微带天线的设计采用天线阵列,提高了天线捕捉能量的灵敏度,天线打样样品实际测量在2.4GHz～2.5GHz整个频段内S11均小于-10dB。阻抗匹配电路设计简单,阻抗匹配电路ADS仿真在2.4GHz～2.5GHz整个频段内S11均小于-10dB。四倍压整流电路提高了RF-DC的转换效率,能使电压放大四倍输出。实验结果表明,2.4GHz～2.5GHz的RF能量收集系统达到了设计要求,可以有效收集环境中2.4GHz～2.5GHz频率内的能量,系统输出直流电压最大可达1.628V。     

一款用于无线胶囊内窥镜的微带天线设计与仿真

基于时域有限差分方法,采用真实人体数字三维模型,仿真了天线在人体消化道内辐射情况,分析了天线结构参数对天线辐射性能的影响。针对无线胶囊内窥镜(Wireless Capsule Endoscopy,WCE)在人体消化道内工作特点,设计了一款能够用于发送消化道内图像数据的WCE微带天线,该微带天线谐振频率为500 MHz,输入回波损耗S11-10 dB时相对带宽为8%,带内VSWR2.0,最后采用仿真优化后的结构参数和材料制作了天线,并进行了测试,得到了满足实际应用要求的微带天线。     

一种宽频带四单元微带天线阵设计*

综合运用了H型缝隙耦合馈电技术和引入空气层技术展宽了天线的频带,设计出一个工作在Ku波段的宽频带微带天线单元并组成四单元阵列。该天线由两层介质板构成,并利用180°反相馈电抑制了高次模的耦合激励,降低了交叉极化电平。使用三维电磁场仿真软件(Ansoft HFSS)对微带天线进行仿真优化,仿真结果表明,天线单元性能良好,相对阻抗带宽(S11≤-10 dB)为8.5%,增益为8.05 dB。四单元天线阵列相对阻抗带宽(S11≤-10 dB)达到16.6%,增益为13.7 dB。天线阵列性能良好,设计方法具有很好的可扩展性。归纳总结出的介电常数计算式也具有普遍性。     

适用于太赫兹通信系统的E形微带天线设计

设计了一种用于太赫兹通信系统的E形微带天线,并利用高频结构仿真软件(HFSS)对设计天线进行仿真。E形微带天线通过在矩形微带天线上加载两条平行缝隙槽以获得宽频带特性。仿真结果表明设计天线的-10dB相对带宽达到29%(从1.394THz到1.87THz),同时给出了该天线的驻波比曲线图和增益曲线图。研究结果显示该E形天线结构简单,能够满足无线通信系统的要求。     

北斗宽波束“U”型槽双频微带天线的设计

基于北斗导航系统的实际通信需求,要求接收天线具有多频带、宽波束、小型化等特点,为此选定设计一款矩形贴片微带天线。结合微带天线的双频圆极化理论,采用同轴线的馈电方法,设计了一款在贴片上开“U”型槽的双频微带天线,使微带天线可以同时工作在北斗B2频段（1210±10MHz）和B3频段（1268±10MHz）,实现了微带天线的双频化,而且减小了天线尺寸。通过HFSS对该天线进行了仿真和参数优化,结果表明,天线回波损耗S11小于-20dB;天线增益大于3dB;双频内的轴比小于6dB;具有较宽的波束,较好的圆极化性能,较小的尺寸,可达到设计要求;而且,电路的设计方法简单,制作工艺简单,可为实际的应用提供参考。     

原油含水率测量系统中螺旋天线的设计

针对目前我国原油含水率高的特点,对原油含水率的实时测量研究有着非常重要的研究意义.根据螺旋天线的基本原理设计了一款用于原油含水率测量的收发天线,该天线在2 ～3 GHz频段内,回波损耗(S11)均小于-10 dB,在2.45 GHz频点的传输损耗(S12)值为-11.3 dB,仿真增益达到11.4 dB.为了提高测试的精确度,对螺旋天线加了圆锥形的屏蔽罩,仿真结果均满足要求.进一步,根据仿真得到的天线参数制作了3款天线,每款天线的S11在带宽内均满足要求,并对任意两款天线进行S12的测量.测量结果表明,当距离为150 mm时,实测的其中两款S12值为12.1 dB,这与仿真的S12值相近,从而最终选定该组天线作为收发天线.     

一种矩形微带整流天线的研究与设计

微波整流是无线输电中的一个重要环节,为完成微波能量的接收,设计了一个结构简单、整流效率高的贴片矩形微带整流天线,此整流天线包括矩形微带天线、输入低通滤波器、整流二极管及输出滤波器。该整流天线的面积小,配合其他装置组成的微波输电系统,可方便地应用于传统有线输电无法应用的场合。通过系统仿真以及实验测试,验证了整流天线的可行性及其高效率,实际测量后计算出整流效率高达63．4％。     

一种高增益宽频带圆极化微带阵列天线的研制

针对微带天线阻抗匹配带宽一般较窄的自身缺陷,基于相控阵雷达天线的应用背景,设计了一种工作在X波段的双层圆极化微带天线结构,且优化发现,其各电磁参数良好。为提高其增益,还在此基础上设计并最终制作了双层2×2结构的微带天线阵列,其实测性能与设计值相符,增益达到10.7dB,带宽1.2GHz,相应轴比为4dB,符合圆极化要求。     

一种433MHz小型化螺旋形印刷天线的设计

采用微带线在介质基片上模仿螺旋天线的走线形式,设计了一种433 MHz小型化螺旋形印刷天线,减小了天线的结构尺寸。采用仿真软件HFSS对天线的主要结构参数进行分析和优化,推导出了天线的最佳结构参数,并通过加载无源集总元件的方法改进了天线的阻抗性能。对回波损耗、增益进行了研究,结果表明:S(1,1)<-10 dB的有效带宽为3.4 MHz(431.5 MHz~434.9 MHz),在433 MHz谐振频点处的S11为-24 dB,有效增益为-4.14 dB。     

X波段超轻薄整流天线设计

为解决无人机等移动目标领域的微波无线传能问题,文章设计了一种适用于微波无线能量传输系统中的10 GHz轻薄微波整流天线。该天线为线极化微带天线,天线印刷制作于厚度为0.254 mm(约0.008λ₀,其中λ₀为天线工作波长)的介质基板上,整流电路采用MA4E1317肖特基二极管作为整流器件,并且通过导电过孔与天线金属地相连接。该天线尺寸为117 mm×117 mm×0.254 mm。加工测试了整流天线样品,测试结果表明,该整流天线在天线接收功率为16 dBm时,整流效率达到62%。     

A novel RF energy harvesting cube based on air dielectric antenna arrays

In this article, a new 2 × 2 circular microstrip antenna array with air dielectric layer for ambient RF energy harvesting has been proposed. Two pairs of arc‐shaped slots located close to the boundary of the circular microstrip patch have been designed for achieving dual‐band response and extending the frequency bandwidth. The antenna has a frequency bandwidth from 1.85 to 1.93 GHz and from 2.0 to 2.1 GHz which can cover GSM‐1800 and UMTS‐2100 bands. At the frequency of 1.89 and 2.05 GHz, the measured gain is 5.3 and 6.6 dBi, respectively, and high gain of 3.8‐9.3 dBi has been achieved over the whole band. Also, a broadband rectifier that can cover all the bandwidths of the antenna array is designed for the rectenna, which has the maximum rectifying efficiency of 53.6%. Finally, a cube device formed of four antenna and four rectifiers is designed to harvest RF energy, whose maximum output DC voltage is 2.3 V and the maximum output power is 4 mW that can drive four LEDs and an electronic watch.     

A compact omnidirectional dual‐circinal rectenna for 2.45 GHz wireless power transfer

A compact dual‐circinal rectenna with omnidirectional characteristic is designed for microwave wireless power transmission at 2.45 GHz. A novel dual‐circinal receiving antenna with the reflection coefficient of ?32.5 dB is proposed which is formed by expanding folded curves. By designing an impedance matching network with a 60 ° radial stub and a single stub, a rectifier is presented with the maximum efficiency of 55.6 % and the output dc voltage of 1.19 V under the input power of 0 dBm. Simulation and measurements have been carried out for the antenna and the rectifier. The measured results agree well with the simulated value. The results of rectenna experiment show that the maximum conversion efficiency is 51% at 2.45 GHz when the input power is 0 dBm. The proposed rectenna has the characteristics of compact size and omnidirectional harvesting which are advantageous in RF energy harvesting applications.     

一种双频段圆极化移动导航终端天线的设计

给出了一款应用于北斗导航卫星系统(CNSS)B1频段/S频段的双频圆极化缝隙天线的设计方法。该天线采用微带线进行馈电,在地板上开有两个方形螺旋槽,其总槽长度大约均为一个自由空间操作波长。通过调节螺旋槽的终点处的长度即可获得最适宜的轴比,从而实现圆极化。另外,还可以通过调节螺旋槽的宽度来获得较大的轴比带宽。在地板中央切去一个圆环形槽可增大感应电流的路径,从而降低圆极化的中心频率。通过仿真软件HFSS对天线结构参数进行优化设计,并制作实物。其仿真及实测结果表明:回波损耗小于-10 dB的阻抗带宽为38.5%,且在阻抗带宽内天线的相对轴比带宽也达到了大约5%。     

Design of perfect electrical conductor wall‐loaded 2.45 GHz high‐efficiency rectenna

A 2.45 GHz industrial, scientific and medical band rectenna with a two‐layered structure for various applications involving microwave wireless power transmission (WPT) has been designed and measured in this article. A microstrip antenna with two perfect electrical conductor walls loaded for gain enhancement is designed. In addition, a typical single‐diode compact radio frequency (RF) rectifier with a series bandpass structure is presented. The simulated RF to dc conversion efficiency of the rectifier is above 50% when the input power ranges from 0 to 28 dBm. The fabricated rectenna is compact with a dimension of 0.5λ × 0.5λ. A RF to dc conversion efficiency of about 73% is achieved under received power density of 38.5 W/m² with a 500 Ω dc load. Due to the integration design of antenna and rectifier, the proposed rectenna is suitable to be well applied in miniaturization of rectenna array.     

A broadband circularly polarized slot antenna with a compact microstrip to CPW transition

A simple structure of broadband circularly polarized slot antenna based on coplanar waveguide (CPW) feeding is proposed in this article. To obtain circular polarization with a single feed, a transition from microstrip to CPW is designed to excite the even and odd modes of the CPW simultaneously. By adjusting the relative position and dimensions of the two circular patches introduced at the end of microstrip line and CPW, a 90° phase difference between two modes can be produced. When the two modes are coupled into the wide slot antenna, broadband circular polarization operation can be realized. The 10‐dB reflection coefficient bandwidth of the proposed antenna is 88.2% (2.49‐6.42 GHz) and 3‐dB AR bandwidth attains 50% (2.72‐4.49 GHz).     

Serial‐feed for a circular patch antenna with circular polarization suitable for arrays

A compact sequential‐rotation array with serial feed and three probes using multi‐layer substrate is proposed. The most compact shape for the microstrip patches are selected with the optimization for the axial ratio and return loss bandwidth. The gain, return loss, and axial ratio bandwidths of the antenna are improved significantly by converting three patches to one circular. The patch radius and the position of probes are selected to form circular Poynting vectors around it where the maximum power is present at large frequency range. While the two layers of the structure use similar board this structure only uses a substrate and three simple pins. Also the total area of the antenna is limited to the microstrip patch and it has a straightforward fabrication steps. So the wideband antenna is relatively inexpensive and compact. The antenna has 21.4% 3 dB axial ratio bandwidth in simulation and 21.1% in fabrication. Consequently, the serial‐multi‐fed circular patch with unique angular and phase arrangements is suitable for many applications as the antenna arrays. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:529–535, 2014.     

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.     

Offset‐fed trapezoidal monopole antenna for broadband circular polarization

A novel broadband circularly polarized monopole antenna consisting of an isosceles trapezoidal monopole antenna which is offset fed by a microstrip line is presented. By choosing an appropriate offset, it is possible to establish two orthogonal current components that are out of phase by 90° and thus producing circular polarization. The axial ratio bandwidth of the proposed antenna has been further increased by adding a vertical slot parallel to the microstrip feed line. The measured results show that the proposed antenna has a 34.57% (1.89 GHz to 2.68 GHz) 3 dB axial ratio bandwidth. The ?10 dB reflection coefficient bandwidth is 122.53% (1.04 GHz to 4.33 GHz). The advantages of the proposed antenna are simplicity and a broad 3 dB axial ratio bandwidth.     

Dual‐band aperture‐coupled rectenna for radio frequency energy harvesting

The article presents a dual‐band aperture‐coupled rectenna for radio frequency (RF) energy harvesting at 2.45 and 5 GHz application. The rectenna consists of a dual‐band π‐shaped slot‐etched aperture‐coupled antenna, designed at the lower substrate of two FR4 substrate layers and a dual‐band rectifier. The proposed antenna design also introduces the harmonic suppression of third‐ and higher order harmonics, ranging from 6 up to 10 GHz from the asymmetrical stubs design at the transmission feedline. The dual‐band rectifier is designed to operate at 2.45 and 5 GHz frequency, successfully achieving high conversion efficiency at 68.83% and 49.90% with the optimum load resistor of value 700 Ω and 1.1 kΩ. The minimum DC voltage of 0.167 and 0.236 V with 0 dBm RF input power can be increased when greater RF power is being applied to it, increasing its flexibility to cater various low‐power applications.