基于FRID的充值消费卡系统设计【物联网开题报告外文翻译说明书论文】.zip
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基于FRID的充值消费卡系统设计【物联网开题报告外文翻译说明书论文】.zip,物联网开题报告外文翻译说明书论文,系统设计开题报告,基于RFID的,系统设计开题,基于RFID 的,基于RFID,论文开题报告,系统开题报告,基于 RFID 的,基于 RFID
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毕 业 设 计(论 文)任 务 书1本毕业设计(论文)课题应达到的目的: 通过本次毕业设计,学生应掌握基于FRID的充值消费卡系统设计的相关开发技术、原理和使用方法,学会查阅资料的方法和阅读一般专业英文文献和期刊等,为以后进行项目设计或深造时查阅资料奠定基础,通过本课题能对RFID、消费和管理方面的知识有了进一步的了解,熟悉并掌握RFID电路设计及RFID技术应用有关方面的知识。能够综合分析目前国内外该课题的研究现状,结合所学的专业技术,提出结合应用实际的解决方案。通过论文的撰写锻炼按规范要求完成论文的能力。 2本毕业设计(论文)课题任务的内容和要求(包括原始数据、技术要求、工作要求等): 由于RFID的消费卡不仅满足了消费者的特殊要求,而且商家可以将优惠和积分等营销手段附加于消费卡中,因此消费卡受到消费者与商家的欢迎。基于这一背景,研究这一种成本低廉和稳定性高的消费卡管理系统具有很强的实用性和广阔的市场前景。本课题主要用到射频识别技术,是利用射频信号和空间耦合传输特性,实现对被识别物体的自动识别。IC卡与阅读器之间通过耦合元件实现射频信号的空间耦合,在耦合通道内,根据时序关系,实现能量传递和数据交换。以单片机为核心控制器件的消费卡识别系统,通过单片机对射频卡读写器等器件的控制。实现射频读卡器电路设计,实现基于RFID的充值消费卡系统软件设计。总结和分析开发原型的过程,设计论文的结构,完成毕业论文的撰写。总结和分析开发原型的过程,设计论文的结构,完成毕业论文的撰写。 毕 业 设 计(论 文)任 务 书3对本毕业设计(论文)课题成果的要求包括图表、实物等硬件要求: 本课题要求是设计基于FRID的充值消费卡系统,该系统能够对卡进行充值,消费者能够查询RFID充值卡的余额,查询消费记录和修改登录密码等读写和管理。最终成果包括:各功能模块的设计,功能实现;源程序代码;设计说明书。符合毕业论文撰写规范的论文和系统说明书。 4主要参考文献: 1.谢磊,殷亚凤,陈曦,陆桑璐,陈道蓄.RFID数据管理:算法、协议与性能评测J.计算机学报,2013(03):457-470. 2.周永彬,冯登国.RFID安全协议的设计与分析J.计算机学报,2006(04):234-254 3.万学春,亓晓彬,龙广钱.RFID控制应用系统中串行通讯的实现J.机电工程技术, 2015(11):384-388. 4.邵明媚.一款RFID读写器天线的设计与研究D.北京:北京邮电大学,2013. 5.岳克强.RFID多标签防碰撞算法研究及应用D.浙江:浙江大学,2014. 6.徐志枢.RFID读写器及天线研究D.北京:北京邮电大学,2009. 7.童乔凌.RFID阅读器芯片设计及通讯算法研究D.湖北:华中科技大学,2010. 8.解光军,顾云海,夏禹根.用于RFID的自动天线调谐系统的设计J.电子测量与仪器学报, 2009(03):123-156. 9.谈熙.超高频射频识别读写器芯片关键技术的研究与实现D.上海:复旦大学,2008. 10.韩益锋.射频识别阅读器的研究与设计D.上海:复旦大学,2005. 11.佐磊.RFID调制方式测试方法的研究与仿真D.湖南:湖南大学,2009. 12.陈传波,杜娟,张智杰.WIN32下基于RS232C协议的串口通信方法及应用研究J.南昌大学学报(工科版),2005(03):78-103. 13.黎步银,姜胜林,吕文中,周东祥.基于C语言的串口通讯程序设计J.传感技术学报, 2002(01):109-124. 14.高婷.计算机软件数据接口的应用分析J.计算机光盘软件与应用,2012(18):93-107. 15.陈百良.单片机C语言与汇编语言的混合编程J.科技信息(科学教研), 2008(06):140-169. 16.赵亮,侯国锐编著.单片机C语言编程与实例M.北京:人民邮电出版社, 2003. 17.朱博,许伦辉.Keil C51中函数指针的使用J.单片机与嵌入式系统应用,2008(05):42-90. 18.施大发,王辉.基于Keil C51编译器的程序优化设计J.电脑编程技巧与维护, 2010(02):23-44. 19.王常钰.使用C51高级语言设计单片机应用系统J.科技风, 2012(06):293-320. 20.冯建雨.电子元器件的焊接技巧J.山东农机化,2008(07):324-340. 21.谭淑梅.简析STM32单片机原理及硬件电路设计J.大庆师范学院学报,2014(06):221-249. 22.常萌,石芳.基于Altium Designer的数码管显示电路的PCB板设计J. 煤炭技术, 2011(09):23-36. 毕 业 设 计(论 文)任 务 书5本毕业设计(论文)课题工作进度计划:起 讫 日 期 工 作 内 容 2015.12.152016.01.02 撰写及修改开题报告、外文参考资料及译文、论文大纲并提交开题报告、外文参考资料及译文、论文大纲 2016.01.052016.04.05 拟定论文提纲或设计说明书(下称文档)提纲;提交基本完成的毕业设计创作成果以及文档的撰写提纲 2016.04.062016.04.10 中期检查(含毕业设计成果验收检查) 2016.03.202016.04.20 进行毕业设计文档撰写; 2016年4月20日定稿截止 2016.04.142016.05.08 1、学生进行毕业设计文档撰写。若是计算机软件开发类课题,需撰写不少于2000字的软件使用说明书; 2、5月1日前,做好答辩安排,学生回校进行答辨 3、2016年5月08日为学生毕业设计文档定稿截止日。 2016.05.092016.05.24 1、毕业设计答辩;2、答辩未通过同学进行二次答辩; 3、5.16-5.29发布及报送毕业设计(论文)成绩;报送毕业设计(论文)信息表给教务处。 2016.05.162016.06.05 根据答辩情况修改论文相关资料,并上传最终稿,上交纸质稿;完成毕业设计全套材料(含电子稿)提交(含网上提交)工作 所在专业审查意见:通过负责人: 2015 年 12 月18 日 毕 业 设 计(论文) 开 题 报 告 1结合毕业设计(论文)课题情况,根据所查阅的文献资料,每人撰写不少于1000字左右的文献综述: 本课题研究的题目是基于RFID的充值消费卡系统设计。本课题所研究的RFID消费系统可实现对卡进行充值,消费者能够查询RFID充值卡的余额,查询消费记录和修改登录密码等读写和管理。 RFID是物联网的重要技术之一。从信息传递的基本原理来说,射频识别技术在低频段基于变压器耦合模型(初级与次级之间的能量传递及信号传递),在高频段基于雷达探测目标的空间耦合模型(雷达发射电磁波信号碰到目标后携带目标信息返回雷达接收机)。1948年哈里斯托克曼发表的“利用反射功率的通信”奠定了射频识别射频识别技术的理论基础。射频识别技术的发展可按十年期划分如下: 1940-1950年:雷达的改进和应用催生了射频识别技术,1948年奠定了射频识别技术的理论基础。 1950-1960年:早期射频识别技术的探索阶段,主要处于实验室实验研究。 1960-1970年:射频识别技术的理论得到了发展,开始了一些应用尝试。 1970-1980年:射频识别技术与产品研发处于一个大发展时期,各种射频识别技术测试得到加速,出现了一些最早的射频识别应用。 1980-1990年:射频识别技术及产品进入商业应用阶段,各种规模应用开始出现。 1990-2000年:射频识别技术标准化问题日趋得到重视,射频识别产品得到广泛采用,射频识别产品逐渐成为人们生活中的一部分。 2000年后:标准化问题日趋为人们所重视,射频识别产品种类更加丰富,有源电子标签、无源电子标签及半无源电子标签均得到发展,电子标签成本不断降低,规模应用行业扩大。 2010年以来,由于经济形势的好转和物联网产业发展等利好因素推动,全球RFID市场也持续升温,并呈现持续上升趋势。同时,RFID的应用领域越来越多,人们对RFID产业发展的期待也越来越高。目前RFID技术正处于迅速成熟的时期,许多国家都将RFID作为一项重要产业予以积极推动。美国在RFID的推广与应用上走在世界前列,利用RFID技术带来的经济效益一直在飞速增长。据Sanford C. Bernstein公司的零售业分析师估计,通过采用RFID,沃尔玛每年可以节省83.5亿美元,其中大部分是因为不需要人工查看进货的条码而节省的劳动力成本。尽管另外一些分析师认为80亿美元这个数字过于乐观,但毫无疑问,RFID有助于解决零售业两个最大的难题:商品断货和损耗(因盗窃和供应链被搅乱而损失的产品),而现在单是盗窃一项,沃尔玛一年的损失就差不多有20亿美元,如果一家合法企业的营业额能达到这个数字,就可以在美国1000家最大企业的排行榜中名列第694位。研究机构估计,这种RFID技术能够帮助把失窃和存货水平降低25%。而在我参阅的以下文献中,国内外科学家利用多种方法解决了RFID发展过程中面临的种种问题。有的设计了一种防碰撞算法,以解决在多个RFID标签短距离同时工作时的信号碰撞问题,使得多个标签可以同时工作。有的文中以RFID的数据管理为切入点,从算法、协议以及性能评测3个层面对RFID的研究工作进行阐述与分析,着重介绍了RFID的防冲突算法、认证与隐私保护协议以及真实环境下系统的性能评测与分析等方面的研究成果及进展。但是,目前中国无源射频市场还处于发展的初期,核心技术急需突破,商业模式有待创新和完善,产业链需要进一步发展和壮大,只有核心问题得到有效解决,才能够真正迎来RFID无源射频市场发展。 参考文献 1.谢磊,殷亚凤,陈曦,陆桑璐,陈道蓄.RFID数据管理:算法、协议与性能评测J.计算机学报,2013(03):457-470. 2.周永彬,冯登国.RFID安全协议的设计与分析J.计算机学报,2006(04):234-254 3.万学春,亓晓彬,龙广钱.RFID控制应用系统中串行通讯的实现J.机电工程技术, 2015(11):384-388. 4.邵明媚.一款RFID读写器天线的设计与研究D.北京:北京邮电大学,2013. 5.岳克强.RFID多标签防碰撞算法研究及应用D.浙江:浙江大学,2014. 6.徐志枢.RFID读写器及天线研究D.北京:北京邮电大学,2009. 7.童乔凌.RFID阅读器芯片设计及通讯算法研究D.湖北:华中科技大学,2010. 8.解光军,顾云海,夏禹根.用于RFID的自动天线调谐系统的设计J.电子测量与仪器学报, 2009(03):123-156. 9.谈熙.超高频射频识别读写器芯片关键技术的研究与实现D.上海:复旦大学,2008. 10.韩益锋.射频识别阅读器的研究与设计D.上海:复旦大学,2005. 11.佐磊.RFID调制方式测试方法的研究与仿真D.湖南:湖南大学,2009. 12.陈传波,杜娟,张智杰.WIN32下基于RS232C协议的串口通信方法及应用研究J.南昌大学学报(工科版),2005(03):78-103. 13.黎步银,姜胜林,吕文中,周东祥.基于C语言的串口通讯程序设计J.传感技术学报, 2002(01):109-124. 14.高婷.计算机软件数据接口的应用分析J.计算机光盘软件与应用,2012(18):93-107. 15.陈百良.单片机C语言与汇编语言的混合编程J.科技信息(科学教研), 2008(06):140-169. 16.赵亮,侯国锐编著.单片机C语言编程与实例M.北京:人民邮电出版社, 2003. 17.朱博,许伦辉.Keil C51中函数指针的使用J.单片机与嵌入式系统应用,2008(05):42-90. 18.施大发,王辉.基于Keil C51编译器的程序优化设计J.电脑编程技巧与维护, 2010(02):23-44. 19.王常钰.使用C51高级语言设计单片机应用系统J.科技风, 2012(06):293-320. 20.冯建雨.电子元器件的焊接技巧J.山东农机化,2008(07):324-340. 21.谭淑梅.简析STM32单片机原理及硬件电路设计J.大庆师范学院学报,2014(06):221-249. 22.常萌,石芳.基于Altium Designer的数码管显示电路的PCB板设计J. 煤炭技术, 2011(09):23-36. 毕 业 设 计(论文) 开 题 报 告 2本课题要研究或解决的问题和拟采用的研究手段(途径): 本课题主要研究一套成本低廉和稳定性高的消费卡管理系统,设计基于FRID的值消费卡系统,该系统能够对卡进行充值,消费者能够查询RFID充值卡的余额,查询消费记录和修改登录密码等读写和管理。本课题主要用到射频识别技术,是利用射频信号和空间耦合传输特性,实现对被识别物体的自动识别。IC卡与阅读器之间通过耦合元件实现射频信号的空间耦合,在耦合通道内,根据时序关系,实现能量传递和数据交换。以单片机为核心控制器件的消费卡识别系统,通过单片机对射频卡读写器等器件的控制。具体设计过程中拟采用13.56Mhz的电感耦合天线与其信息编码传输与调制,利用Altium Designer软件设计PCB电路板,利用Keil编写C语言控制程序。实现射频读卡器电路设计,实现基于RFID的充值消费卡系统软件设计。 毕 业 设 计(论文) 开 题 报 告 指导教师意见:1对“文献综述”的评语:该生阅读了一定的文献,对所阅读的文献进行了简要的综述,在写毕业论文时,文献综述部分还应加强 2对本课题的深度、广度及工作量的意见和对设计(论文)结果的预测:本课题深度一般,广度一般,工作量适中,学生应能按时完成毕业设计工作 3.是否同意开题: 同意 不同意 指导教师: 2016 年 01 月 10 日所在专业审查意见:同意 负责人: 2016 年 04 月 22 日说明:要求学生结合毕业设计(论文)课题参阅一篇以上的外文资料,并翻译至少一万印刷符(或译出3千汉字)以上的译文。译文原则上要求打印(如手写,一律用400字方格稿纸书写),连同学校提供的统一封面及英文原文装订,于毕业设计(论文)工作开始后2周内完成,作为成绩考核的一部分。Principle of RFID technique and design of RF antennaSince 1970, the first piece of IC card came from, IC card become when microelectronic technology market growth the fastest one of the products, to 1996 World sale IC card has more than 700 million Zhang 1. But this to use the contact type IC card has its own inevitable shortcomings, namely, the contact point of contamination, corrosion and lack of resistance, greatly reducing the service life of the IC card and the scope of use. In recent years, people began to development and application of non contact IC card to gradually replace the contactless IC card, including radio frequency identification (RFID) card is a kind of typical non contact IC card, it is to realize the data exchange between the system and IC card using wireless communication technology, shows the advantages of using more convenient than ordinary contact IC card, has been widely used in the production of electronic tags or identity identification card. However, RFID needs to realize data exchange using different antenna communication technology in different application environment. Here we will first design by introducing the basic principle of RFID application system to specify the RF antenna is the key to RFID application system, then several typical RFID antenna and its design principle are introduced, finally introduces the use of Ansoft HFSS tools to design RFID an omnidirectional antenna.1. RFID Technology PrincipleTypically, the RFID application system is mainly composed of a reader and a RFID card is composed of two parts, as shown in Figure 1. Among them, the general reader as a computer terminal, to achieve RFID card data read and write, it is composed of control unit, high frequency communication module and antenna and RFID. The card is a passive transponder, is mainly composed of an integrated circuit (IC) chip and external antenna, the RFID chips are usually integrated with RF front-end circuit, logic control, memory 2, and some even put together the basic working principle of antenna integrated on the same chip 3.RFID application system is the RFID card to enter the field of RF reader, induction current obtained by the antenna through the boost circuit as the power source, and the induced current will take information through the RF front-end circuit. The digital signal into a logic control circuit for information processing; and the reply is from the memory access through the logic control circuit back to the RF front-end circuit, finally through the antenna is sent back to the reader. Visible, RFID card and read-write device to realize the data communication process plays the key role is the antenna. On the one hand, passive RFID card chip to starting work circuit needs through the antenna in read write electromagnetic field generated by the antenna gain enough energy; on the other hand antenna determines the RFID card reading and writing device between communication channels and means of communication.Current RFID has been widely used, and has the international standard: iso10536, iso14443, iso15693, ISO18000 and several. These standards in addition to the requirements of the external communication data frame protocol on of working distance, frequency, coupling mode and the physical characteristics of the antenna related technical specification for lattice were Standard Specification for RFID Application system development determines the choice of RFID antenna, are given below has been widely application of various types of RFID antenna and its performance.Fig.1Structure of RFID systemFig.2Equivalent circuit diagram of responder2. RFID antenna typeAntenna of RFID is mainly a coil type, type of microstrip patch, dipole type three basic forms. Among them, less than 1 m close application system of RFID antenna commonly used has the advantages of simple process, low cost of the coil antenna, they mainly work in the low-frequency. And more than 1 m distance should with system needs to use the RFID antenna of microstrip patch type or dipole. They work in the RF and microwave frequency bands. The working principle of these types of antenna is not the same.2.1 coil antennaWhen the RFID antenna coil into the reading and writing device to generate the alternating magnetic field, rfid antennas and read write the interaction between the antenna was similar to that of transformer, coil of both quite in the primary and secondary coils of the transformer. Formed by the RFID antenna coil resonant circuit as shown in Figure 2. It includes RFID antenna coil inductance, parasitic capacitance CP and connected in parallel with a capacitor C2 , the resonant frequency: but PI L C, (C for CP and C2 equivalent parallel capacitance) of RFID application system is by the carrier frequency realize bidirectional data communication of. Insert and usually the appearance of common Id-1 type non-contact type IC card is a small plastic card (85.72m*54.03 mm*0.76 mm), the antenna coil resonant frequency of 13.56 MHz. Currently has developed a minimum area of 0.4mm x 0.4 mm coil antenna 3 short distance RFID application system. Some applications for RFID antenna coil shape is very small, and the need for a certain distance, such as used for animal identification RFID. Coil contour and the area is small, the RFID reading and writing device between the antenna coil mutual inductance m is obviously can not meet the actual use. Usually in the RFID antenna coil with high magnetic permeability Mu iron ferrite materials, in order to increase the mutual inductance, thus compensating coil cross-section decreases.2.2 microstrip patch antennaMicrostrip patch antenna is made up of the radiation patch conductor in the dielectric substrate with metal board on the 4, as shown in Figure 3. According to the antenna radiation characteristics, can be designed into various shapes. Usually the patch conductor patch antenna radiation conductor and the metal floor distance of several 1/10 wavelengths, assuming that the radiation field along the conductor of the horizontal and vertical direction of the two did not change, only along about half wavelength (lambda g/2) the conductor length direction. The radiation of microstrip antenna is basically composed of open edge of the edge of the patch conductor field caused by radiation, to determine the basic, therefore, generally applicable RFID system used in the communication direction small. In order to improve the performance of the antenna and its communication direction, people also put forward different kinds of microstrip slot antenna, such as the design of a 5,6 operating in the 24 GHz of the single slit A circular polarization slot coupled patch antenna is developed in the paper, which is a circularly polarized slot coupled patch antenna, which can be used in the binary data of 1 and 0 and 5.9 for encoding.Fig.3Microstrip antennaFig.4Dipole antennaFig.5Dipole antenna2.3 dipole antennaIn the RFID application system of long-distance coupling, is the most commonly used dipole antenna (also called dipole antenna) 9. dipole antenna and its evolutions as shown in Figure 4, the dipole antenna consists of two segments of the same thickness and length of the straight wire line, the signal from the two endpoints of feed in the middle have certain current distribution on the arms of the dipole antenna current distribution in the space around the excited electromagnetic field. Using the Maxwell equation can calculate the radiation field equation: E = l-ldE = l-l60 alpha theta formula formula Izrsin (alpha theta theta cos zcos) DZ where Iz is the current distribution along the vibrator arm the alpha phase constant, R oscillator is point to the distance of the observation point, theta is the oscillator shaft to the R angle, l single vibrator arm length. Also, also can get the antenna input impedance, input return loss S11, impedance bandwidth and antenna gain. Parameters. When a single vibrator arm length L = lambda / 4 (half wave dipole) and the reactive components of the input impedance is zero, and the input impedance of the antenna can be regarded as a pure resistance. In condition of neglecting the transverse influence of thickness of the antenna, a simple dipole antenna design can take the vibrator length L is an integer multiple of the Lambada / 4, such as the work frequency of 2.45 GHz half wave dipole antenna, the length of about 6 cm. When the requirements of dipole antenna with high input impedance, the figure 4-b folded vibrator.3. RFID RF antenna designFrom the point of view of the principle of RFID technology and RFID antenna type, RFID application the key lies in the characteristics and performance of rfid antennas. The coil antenna implementation technology is mature, although have been widely applied in such as identification, goods labels, RFID application system, but for those requiring high frequency, large amount of information, RFID applications, working distance and direction is not determined by coil antenna is difficult to design to achieve the corresponding performance. Similarly, if the use of microstrip patch antenna, due to the complicated process, high cost, a hasnt been low cost RFID application system. Dipole antenna with radiationThe ability to be strong, simple manufacturing and low cost, and can be designed to be suitable for the full direction of communication RFID application system, therefore, we come to the specific design of a work in 2.45 GHz (international industrial medical research free band) RFID dipole antenna.The half wave dipole antenna model as shown in Figure 4-A. The antenna adopts copper material (conductivity: 5.8e7 s/m permeability: 1) filled with air, is located in the center of the cube. The cube set in vitro surface radiation absorbing boundary. The input signal from the antenna at the center of feed, is also the location of the RFID chip. The working frequency of 2.45 GHz the half wave length is about 61mm, a dipole antenna arm width W is 1 mm, and the infinite thin, because of the influence of antenna arm width, half wave dipole antenna length is 57mm. in the actual Ansoft HFSS tool platform, using the finite element method named10 to simulate the antenna, the input return loss S11 the distribution is as shown in Fig. 5-a, the radiation field of E surface (i.e. maximum radiation direction and the electric field vector plane) direction diagram as shown in figure 5-b. The input impedance of antenna is about 72 psi, voltage in Bobbi (VSWR) is less than 2 when the impedance bandwidth is 14.3% days Line gain is 5-b from figure 1.8. and can be seen in the antenna axis direction, and the antenna is almost no radiation.Out any reaction. In order to obtain the full range of radiation of the antenna in order to overcome the disadvantages, can make appropriate deformation of antenna, such as in the direction that is perpendicular to the dipole antenna arms at the end of the extended quarter wavelength as shown in Figure 4-C. Such that the antenna with a total length of modified for (57.0 mm+2 * 28.5 mm), antenna arm width still for 1 mm. Antenna arms extended a Lambada / 4, the antenna resonance in length, rather than the original half a wavelength. This makes the input impedance of the antenna is greatly increased, the simulation results about 2 K only. The input return loss S11As shown in figure 6-A. Figure 6-b e (antenna) plane radiation field pattern, in which the solid line is the simulation results, black spots for the actual sample data, both results are in good agreement with those that the impedance bandwidth of the design is correct. From figure 6-b can see has been greatly improved in the direction of the original weak radiation, the radiation is similar to the direction of the. Voltage standing wave ratio (VSWR) (VSWR) less than 2.0 was 12.2%. The gain of 1.4, for most of the RFID application system, the dipole antenna can meet the requirements.Fig.6Changed dipole antenna4. concluding remarksAnyway, RFID application key is the antenna design, especially for commodity label with very large market capacity, it is required that RFID can realize omnidirectional wireless data communication and also has the advantages of low price, small size. Therefore, we designed the whole to dipole antenna structure is simple, easy to batch processing and manufacturing is to meet the actual needs. Through the design of actual samples for testing parameters, testing results and the expected results are consistent.RFID技术原理及其射频天线设计自1970年第一张IC卡问世起,IC卡成为当时微电子技术市场增长最快的产品之一,到1996年全世界发售IC卡就有7亿多张。但是,这种以接触式使用的IC卡有其自身不可避免的缺点,即接触点对腐蚀和污染缺乏抵抗能力,大大降低了IC卡的使用寿命和使用范围。近年来人们开始开发应用非接触式IC卡来逐步替代接触式IC卡,其中射频识别(RFID)卡就是一种典型的非接触式IC卡,它是利用无线通信技术来实现系统与IC卡之间数据交换的,显示出比一般接触式IC卡使用更便利的优点,已被广泛应用于制作电子标签或身份识别卡。然而,RFID在不同的应用环境中需要采用不同天线通讯技术来实现数据交换的。这里我们将首先通过介绍RFID应用系统的基本工作原理来具体说明射频天线的设计是RFID不同应用系统的关键。然后分别介绍几种典型的RFID天线及其设计原理,最后介绍利用Ansoft HFSS工具来设计了一种全向的RFID天线。1.RFID技术原理通常情况下,RFID的应用系统主要由读写器和RFID卡两部分组成的,如图1所示。其中,读写器一般作为计算机终端,用来实现对RFID卡的数据读写和存储,它是由控制单元、高频通讯模块和天线组成。而RFID卡则是一种无源的应答器,主要是由一块集成电路(IC)芯片及其外接天线组成,其中RFID芯片通常集成有射频前端、逻辑控制、存储器等电路,有的甚至将天线一起集成在同一芯片上。RFID应用系统的基本工作原理是RFID卡进入读写器的射频场后,由其天线获得的感应电流经升压电路作为芯片的电源,同时将带信息的感应电流通过射频前端电路检得数字信号送入逻辑控制电路进行信息处理;所需回复的信息则从存储器中获取经由逻辑控制电路送回射频前端电路,最后通过天线发回给读写器。可见,RFID卡与读写器实现数据通讯过程中起关键的作用是天线。一方面,无源的RFID卡芯片要启动电路工作需要通过天线在读写器天线产生的电磁场中获得足够的能量;另一方面,天线决定了RFID卡与读写器之间的通讯信道和通讯方式。目前RFID已经得到了广泛应用,且有国际标准:ISO10536,ISO14443,ISO15693,ISO18000等几种。这些标准除规定了通讯数据帧协议外,还着重对工作距离、频率、耦合方式等与天线物理特性相关的技术规格进行了规范。RFID应用系统的标准制定决定了RFID天线的选择,下面将分别介绍已广泛应用的各种类型的RFID天线及其性能。图1射频识别系统原理图图2应答器等效电路图2.RFID天线类型RFID主要有线圈型、微带贴片型、偶极子型3种基本形式的天线。其他,小于1 m的近距离应用系统的RFID天线一般采用工艺简单、成本低的线圈型天线,它们主要工作在中低频段。而1 m以上远距离的应用系统需要采用微带贴片型或偶极子型的RFID天线,它们工作在高频及微波频段。这几种类型天线的工作原理是不相同的。2.1线圈天线当RFID的线圈天线进入读写器产生的交变磁场中,RFID天线与读写器天线之间的相互作用就类似于变压器,两者的线圈相当于变压器的初级线圈和次级线圈。由RFID的线圈天线形成的谐振回路如图2所示,它包括RFID天线的线圈电感L、寄生电容Cp和并联电容C2,其谐振频率为:f=1/(2L C)(式中C为Cp和C2的并联等效电容)。RFID应用系统就是通过这一频率载波实现双向数据通讯的。常用的ID-1型非接触式IC卡的外观为一小型的塑料卡(85.72m54.03 mm0.76 mm),天线线圈谐振工作频率通常为13.56 MHz.目前已研发出面积最小为0.4mm0.4 mm线圈天线的短距离RFID应用系统.某
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