【作者】 张宁；

【导师】 李秀萍；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2011， 硕士

【摘要】 射频识别(RFID)技术是利用电磁场的感应和辐射实现双向通信的一种自动识别技术。近年来,射频识别系统的应用领域日益扩大。相对于低频段的射频识别系统,工作在860MHz-960MHz的超高频段射频识别系统有着读取距离较远,阅读速度较快等优点,是目前国际上RFID技术发展的热点。读写距离是RFID系统中重要的关键参数之一,它由标签天线的增益、标签天线与芯片间的匹配程度以及芯片的读写开启电压所决定,所以标签天线可以说是RFID系统中最重要的部件,因此RFID标签天线的快速设计和测试的研究对RFID技术的成熟和广泛应用具有理论意义和实用价值。本文致力于解决UHF RFID标签天线设计所出现的问题。因此本文在简要介绍RFID系统的工作原理、分类以及UHF RFID标签天线的设计和测量所需要的电磁学知识的基础上,主要研究了RFID标签天线的快速设计、测量以及基于金属表面的标签天线的设计。本文的主要工作包括以下几个方面：(1)提出了两款结构的RFID标签天线,通过调节天线的2个关键尺寸,可以使天线与标签芯片(输入阻抗实部Rchip在(10～80)Ω范围,虚部Xship在(-600～50)Ω范围,且Xchip=-(5～10)*Rchip)在840MHz-930MHz频率范围内的反射系数SH<-10dB。然后结合关键尺寸和神经网络建模,完成了天线的快速设计和优化。(2)在介绍了UHF RFID标签天线阻抗测量方法的基础上,针对同轴测量系统,提出了一种简单准确的标签天线输入阻抗测量方法：基于电磁仿真的阻抗测量方法,并采用此方法对一款标签天线进行测量,测量结果与基于双端口S参数的测量方法的测量结果以及仿真结果都符合较好。(3)从理论上研究分析了金属表面对标签天线输入阻抗以及方向图的影响,并总结了目前论文中已有的基于金属表面的标签天线的三种结构并给出了各种结构的优缺点。同时给出了一款应用于烟盒内表面的标签天线。更多还原

【Abstract】 Radio Frequency Identification (RFID) is an automatic non-contact bidirectional communication identification technology taking advantage of electromagnetic induction and radiation. In recent year, RFID systems are applied in more and more fields, and they have been involved in many aspects of people’s daily life. Comparing with 13.56MHz RFID system,860MHz-960MHz UHF RFID system has farther reading distance and faster speed, etc. Nowadays, it has become a hot spot in RFID research. Reading distance is the most important aspect of an RFID system’s performance. It is dependent on the gain of tag antenna, the power transmission coefficient which is determined by the matching between tag antenna and microchip, and the power sensitivity. So the tag antenna which determines the system’s reading range plays a key role in the overall RFID system.This paper is committed to solve the problems in the research on the design of UHF RFID tag antenna. This paper first introduces working principle, common frequency band, the problems it’s now facing of the RFID system and the knowledge of electromagnetic which is needed in the design and measure of UHF RFID tag antenna. Then mainly research on the quick design and measurement of RFID tag antenna and tag antenna design based on metallic surface. The main work of this paper are:(1) In the third chapter of this paper, two structures of RFID tag antenna proposed for RFID tag antenna quick design and optimization. The two proposed antennas present at least 90MHz (840～930MHz) bandwidth for microchip impedance between (10-j80)Ωand (80-j600)Ωunder the condition of reflection coefficient S11 less than-10dB by changing the antenna’s two key parameters. Then using the ANN models of the two antennas, we can realize the quick design and optimization of the UHF RFID tag antenna. (2) The existed methods to measure the input impedance of UHF RFID tag antenna was first introduced in first section of the forth chapter, then EM simulation based measurement method are proposed in this paper. It is a de-embedding method based on EM simulation for accurate RFID tag antenna measurement using coaxial line and SMA connector. The measurement result agrees well with the result of the equivalent two ports scattering matrix measurement method and the simulated result. (3)The fifth chapter is focus on the research and analyze of the impact of metallic surface on the input impedance, directional diagram and the gain of the RFID tag antenna. And then summarize the three main antenna structures used on the metallic surface and also give the merit and demerit of these three structures.更多还原