【作者】 王嘉；

【导师】 王均宏；

【作者基本信息】 北京交通大学 ， 电磁场与微波技术， 2009， 硕士

【摘要】 射频识别(RFID)系统,有着极其广阔的应用前景,其研究和开发受到各国的重视。UHF频段的射频识别系统以其独特的优势成为国际上研究的热点之一。天线是RFID标签的重要组成部分,而UHF频段的天线受金属表面影响较大,这样基于自由空间设计的RFID系统的性能在金属表面上会变得不稳定。本文准备对UHF频段金属表面薄型(易共形)标签天线进行研究,并设计出一到两种可用的标签天线。UHF频段RFID系统的优劣取决于其读写距离,而对读写距离影响最大的是天线的匹配状况以及天线的增益,本文针对这两个关键问题的研究取得了一些成绩,主要的工作和创新之处如下:1.设计出了一种同轴线馈电切口微带贴片天线,该天线在结构上有所创新,是基于厚度为0.635mm的薄型介质板设计的,其峰值增益能达到-4.5dBi,输入阻抗的变化范围可达(5～95~+)+j(100～350~+)Ω。天线利用同轴线进行馈电,芯片与同轴线相连,结构简单,制作成本低。根据设计结果制作了天线并进行了测量,测量结果与仿真结果基本一致。2.设计出了一种波导馈电的微带环缝天线,该天线同样也是基于厚度为0.635mm的薄型介质板设计的,其峰值增益能达到-4.7dBi,输入阻抗的变化范围可达和(8～150~+)+j(80～600~+)Ω,设计时是将芯片与天线直接集成在一起的,降低了成本,适宜大规模的RFID标签天线生产。实际制作了天线并进行了测量,测量结果与仿真结果基本一致。3.对不同金属环境下天线性能的变化进行了仿真分析,主要得出了以下三点结论:(1)天线周围有金属时,并且当天线距金属为λ/4(λ为工作频率点对应的波长)的奇数倍时,其增益会被增强,而偶数倍时其增益会被减弱;(2)当天线贴在金属表面时,沿电流流向增大金属表面的长度会令增益先增后减,垂直于电流流向增大金属表面的长度则会令增益持续减小;以上两种情况对天线回波损耗影响不大;(3)天线沿电流流向呈圆柱形弯曲时增益会不断减小,当垂直于电流流向弯曲时,增益会持续增大,弯曲的情况会对输入阻抗和回波损耗影响较大。更多还原

【Abstract】 Radio frequency identification (RFID) system has a wide range of application in future, and many countries paid lots of attention on it. As a result of its advantage, UHF RFID system now is the international hot spot. The RFID antenna in UHF frequency band is the key component of RFID tag, but the antenna that design on free space can be influenced greatly by metallic surface, which will cause the instability of the system. Some work on the thin (easy to be conformal with object) UHF RFID tag antenna for metallic surface is done and some kinds of antennas that can be used on metallic surface are designed in this paper.The performances of UHF RFID system largely depend on its reading range, and the reading range is greatly influenced by the gain and impedance matching of antenna, the paper makes some success at these two points, the main work and innovation points are as below:1. A microstrip patch antenna with a feeding line at incison is designed. Its structure is something new, used on a dielectric layer with the thickness of 0.635mm, the peak gain is -4.5dBi, and the Variational range of input impedance is(5～95~+) + j(100～350~+)Ω, it is fed by feeding line. Its structure is simple and the cost is low. The antennas are produced based on the design results and measured. Measurement results and simulation results are basically the same.2. A circular slot antenna fed with CPW is designed. Also its structure is and used on the layer with a dielictric thickness of 0.635mm, the peak gain is -4.7dBi, and the Variational range of input impedance is (8～150~+) + j(80～600~+)Ω, it is designed to be integrated with the chip, so the cost is reduced; it is suitable for mass production. The antenna is produced. Measurement results and simulation results are basically the same.3. The antennas with different kinds of metal environment are simulated and analized. The results can be sorted in three conditions: First, in the condition that there is metal aroud the antenna, if the distance between the antenna and the metal is about even times ofλ/4 (λis the wavelength corresponding to operating frequency), the gain will be enhanced by metal; If the distance is around double times ofλ/4, the gain will be weakened. Second, increasing the length along surface current will contribute to the gain at first, and then the opposite; while increasing the length calibration to surface current will reduce the gain constantly. In these two conditions above, the return loss is little influenced. Third, the antenna is bent along the cylindrical metallic surface. When it is bent along the surface current, the gain will keep reducing; in the opposite condition, the gain will be increased constantly.更多还原