【作者】 卿剑；

【导师】 朱青；

【作者基本信息】 湖南大学 ， 电路与系统， 2008， 硕士

【摘要】 射频识别作为近年来逐渐兴起的一种非接触式自动识别技术,在各领域的应用越来越广泛。目前,超高频射频识别读写器的射频模拟前端电路存在元器件数目多、成本高、功耗大等问题。针对这一情况,论文以915MHz读写器射频前端电路为研究对象,对读写器射频前端的拓扑结构、参数选择、电路设计与调试等方面作了详细的分析和研究,主要研究内容有:(1)阐述了射频识别技术的发展、原理和射频识别系统的构成,分析了ISO/IEC18000-6 Type B标准,研究了射频通信电路设计的相关理论。在给出读写器主要技术基础上,提出了读写器总体设计框图,并详细分析了射频前端电路的结构和工作原理。论文将射频前端电路分为发射电路和接收电路两部分分别进行设计和调试。(2)在发射电路中,针对超高频RFID读写器的工作特点,设计了基于数字频率合成器LMX2315的锁相环路,给出了锁相环伪随机跳频程序流程图。仿真结果表明该锁相环电路具有良好的性能,适用于实际的RFID读写器电路设计。选用合适的IC,设计了符合ISO/IEC18000-6 Type B标准要求的射频调制,射频功率放大电路和电源管理电路,实现了读写器输出功率可调,射频放大器电源可管理的功能,有效地减少了读写器的功耗。(3)在接收电路中,设计了基于射频功率检测芯片AD8319的反射功率检测电路,能持续检测负载匹配状态,实现无负载保护功能。并针对超高频RFID读写器的工作特点,选用合适器件,设计了零中频接收电路,减少了外接元件,降低了读写器成本和功耗。(4)根据读写器总体设计要求,开发了读写器样机,对其射频模拟前端电路进行了分模块调试,给出了实验结果并对实验数据进行了分析。通过对读写器样机测试表明,其输出功率、读卡距离、功耗等技术性能指标均达到或优于设计标准要求,样机运行稳定可靠,达到了预期的设计目标。更多还原

【Abstract】 Radio Frequency Identification (RFID) has been gradually used in all fields as a new contactless automatic identification technology developed in recent years.Aiming at the weakness of RF analogy front end circuit in ultra high frequency (UHF) RFID reader, such as too many components, high cost, high power consumption, and so on, topology, parameter selection and circuit design are analyzed and studied in detail in this paper. The main contents are as follows:Firstly, the development, working principles and system structure of RFID were introduced, the ISO/IEC 18000-6 type B standard was analysed, and the theory of RF communication system was researched. According to the technical specifications of RFID reader, the paper offers the overall design diagram of the reader and analyzes the structure, working principles and interfaces of the RF analog front end in detail.The RF analogy front end circuit includes transmission circuit and receiver circuit.Secondly, this paper designs the PLL circuit based on digital frequency synthesizer LMX2315, which aims at the requirement and the character of UHF RFID reader. Then it presents pseudorandom frequency hopping program flow chart of PLL. Simulation results show that this PLL circuit has good performance and can be applied to the practical RFID reader circuit. By choosing appropriate IC, this paper designs the RF modulation circuit, RF power amplification circuit and power management circuit which are compatible with the ISO/IEC 18000-6 type B standard. The reader power consumption is reduced effectively, because the reader output power is adjustable and the RF amplifier supply is managed.Thirdly, this paper designs the reflected power detection circuit based on AD8319, and realizes non-load protection by detecting the impedance matching between reader and load continually. Aiming at the requirement and the character of UHF RFID reader, zero-IF circuit has been adopted to reduce the reader cost and power consumption further.Finally, under the system design requirements, a UHF RFID reader prototype was developed. Its hardware was experimented and debugged, and the experimental results and data were given out.The test results show that the prototype’s output power, read distance and power consumptio are attained or better than design standards required. The prototype can work stably and achieve the expected goals.更多还原