【作者】 王旭；

【导师】 王剑钢；

【作者基本信息】 吉林大学 ， 生物医学工程， 2009， 硕士

【摘要】 射频识别(Radio Frequency Identification,简称RFID),又称电子标签技术,是20世纪90年代兴起的一种自动识别技术。它是一项利用射频信号通过空间耦合(交变磁场或电磁场)实现无接触信息传递并通过所传递的信息达到识别目的的技术。射频识别技术无需光学可视、无需人工接触可完成信息输入和处理、操作快捷方便、迅速发展等优点,广泛应用于生产、物流、交通、医疗、食品、防伪等领域。射频识别系统从狭义的角度说,由两个部分组成,即电子标签和阅读器。广义的射频识别系统还应该包括实际应用中的后台软硬件,甚至包括所构建的数据传输网络。本论文以医疗机构中的RFID系统为例,重点讨论了有源RFID系统在医院信息管理中人员管理、物品管理及检验科室就诊管理等几方面的应用。同时本文提出了一种2.45GHz有源RFID系统的设计与实现。设计中使用nRF2401A射频收发芯片实现射频传输,以MSP430系列低功耗单片机作为控制核心实现射频识别功能。电子标签中选用MSP430F1122单片机,阅读器中选用MSP430F149单片机。在实现射频识别功能的基础上,本系统还具备基于CAN和485总线的远程通信功能、标签低电检测及报警功能、实时时钟、处理器监督、键盘及显示功能、温度检测与SD存储等应用功能,可以使本系统在更多应用场合发挥作用,对现实应用、实际生产有一定的指导意义。更多还原

【Abstract】 The paper discusses a design of active RFID tags and reader which work at 2.45GHz ISM band. The system is hoped to be used in the Medical institutions.RFID OverviewRadio Frequency Identification (RFID), also known as e-tag technology, is an automatic identification technology, brought about in 20th century 90’s. It is an identification technology which uses radio frequency signals through space coupling to achieve non-contact transmission of information and relies on the transmission of information to achieve identification.The technology usually uses small wireless transceiver as the tag to mark an object, and the tag takes some information about the object. The wireless transceiver called tag launches radio waves which takes the information to the nearly data reader. The reader can be applied to these data collection and processing, and can handle computer and network to send the data.At present, a lot of radio frequency identification research and development are concerned about its application in the field of medicine. RFID system in the field of medicine and medical institutions have been involved in the aspects such as application of identification, drug tracking, tracing a history of exposure to infectious diseases, goods management, human function expansion and so on.The design of Active RFID SystemThe paper discusses a design of active RFID system working at 2.45GHz ISM band. It uses RF transceiver chip nRF2401A to complete RF transmission, and the control core is the MSP430 family of low-power MCU to complete Radio Frequency Identification. In order to make the system be able to fit in the medical institutions in real-time locating system applications, to improve the personnel, materials management efficiency, the design adds many additional features except for the basic function, such as RS-232 serial communication, RS-485 or CAN bus Remote communications, processor monitoring, real-time clock, sound and light alarm, LCD display, temperature detection as well as the SD card storage and so on. Therefore the system can meet the majority of occasions the application.Work frequency choiceAt present, the most used are close 13.56MHz radio frequency identification systems. Compared to the former, 2.45GHz range of the RFID system works further, to reach tens of meters or even one meter distance. At the same time, it not only has stronger anti-interference ability, but also can penetrate some metal shielding. Moreover, 2.4GHz ~ 2.48GHz are not required to apply for the use of the world’s only common band permits. So the design in this paper chooses the 2.45GHz work frequency.The choice of the tag power supplyElectronic tags are generally divided into two types of active and passive. Passive tags work by the energy required by electromagnetic coupling unit or antenna, which can be sent from a non-contact reader to the tag. Passive tag identification usually works in a distance of dozens of centimeters to ten meters. Active tags have their own electronic power supply, so the identifying range can up to 100 meters or even tens of meters. However, its battery life subject to the restrictions, life-expectancy of up to 2-5 years. Medical institutions and the surrounding buildings have a larger environment of space, so it requires further transmission distance, and the replacement of the battery is not difficult. So it chooses the active electronic tags.System designThis paper focuses on the active RFID system design and implementation of hardware. Hardware design is divided into two parts: the design of the tag and the reader.The design of the tagThe hardware circuit of the tag including two parts: RF modules and control module.RF modulesRF module uses the chip nRF2401A produced by NORDIC company. nRF2401A is a single-chip radio transceiver for the world wide 2.4-2.5 GHz ISM band. The transceiver consists of a fully integrated frequency synthesizer, a power amplifier, a crystal oscillator and a modulator. Output power and frequency channels are easily programmable by use of the 3-wire serial interface.nRF2401A and its peripheral 50? matching networks, constitute the basic part of RF modules. In order to improve the efficiency of RF transceiver, the module can use power amplifier and antenna. The tag antenna is drawn directly on the PCB board, and the copper ring on circuit board acts as the antenna.Control module The control module selects ultra-low power mixed signal microcontroller MSP430F1122 produced by Texas Instruments (TI). A 200mAh Li-ion battery works as the power supply.The Texas Instruments MSP430 families of ultralow-power microcontrollers consist of several devices featuring different sets of peripherals targeted for various applications. The architecture, combined with five low power modes is optimized to achieve extended battery life in portable measurement applications. The device features a powerful 16-bit RISC CPU, 16-bit registers, and constant generators that attribute to maximum code efficiency.The design of the readerThe reader has many functions, according to their functional modules are as follows: power supply module, control module, RF module, real-time clock, isolation module, remote communication module, display module, keyboard, sound and light alarm.Power supply modulePower supply module uses a 9V AC power. In the circuit many chips need 3.3V DC power supply, but there are some chips need 5V power supply. In order to ensure that reader circuit can work normally, the power supply module must converts the 9V into 3.3V and 5V to drive the different chips. In this paper, there are two same integrated voltage regulator block 7805 change 9V voltage into two 5V voltage loops. One of them is used as 5V power supply, the other one is sent to Regulator tube AMS1117, and be reduced to 3.3V. In order to improve the safety performance of the circuit, add a DC-DC power supply isolation chip and a self-recovery fuse in the power supply module.Control moduleControl module includes controller chips, processor chips monitor, RS-232 download chips etc. The design uses MSP430F149 as the reader’s control chip. The BSL download provides a good way to its system development for Security after the deal. The MCU internal integrated temperature sensor and 12-bit, 8-channel A/D converter which can achieve temperature and voltage monitoring functions.In this paper, use the MAXIM chip production MAX3232ECAE to complete serial communication function. The MAX3232E communications interface devices feature low power consumption, high data-rate capabilities, and enhanced electrostatic-discharge (ESD) protection. A proprietary low-dropout transmitter output stage delivers true RS-232 performance from a +3.0V to +5.5V power supply, using an internal dual charge pump. TPS3823 is processor supervisory circuit produced by TI. It doesn’t need any peripheral circuits. It has features of such as watchdog timer, Reset output available in active-Low; manual reset input and so on. It is faster than the watchdog timer written by software, so it can ensure the reader to work normally for a long time.RF moduleThe basic core of the reader’s RF module is the same as the tag’s. But the reader requires higher transmitting power, so that it can expand the scope of effective reading, improve the accuracy of reading. So add power Amplifier PA2423L and the RF switches UPG2214TK to make improve transmitting power.Remote communication moduleIn this paper, long-range communication module contains CAN bus and RS-485 bus, the practical application can choose either.CAN(Controller Area Network)is a serial bus system, particularly suitable for the formation of intelligent industrial equipment, networks and building automation control systems. CAN has a high transmission speed and high reliability, capable of high-quality high-performance and highly reliable means of monitoring systems, can greatly protocol to meet the user’s design requirements.Microchip Technology’s MCP2515 is a stand-alone Controller Area Network (CAN) controller that implements the CAN specification, version 2.0B. The TJA1040 is the interface between the CAN protocol controller and the physical bus.RS-485 bus is a multi-standard transmitter circuit, the interface uses a pair of balanced differential signal lines, and it permit one transmitter to drive 32 load equipments on two-wire. The SP485E is a family of half-duplex transceivers that meet the specifications of RS-485 and RS-422 serial protocols with enhanced ESD performance.Isolation moduleLong-range communication module’s long lines can introduction the external voltages interfere. In order to avoid it, the design should add the isolation to the module for electrical isolation chip. In this paper, long-range communication module and sound alarm light module use Toshiba’s high-speed optocoupler isolation TPL113 chip to complete the signal isolation. The whole system uses a DC-DC power supply to isolate.Real-time clockThe data from the tags need to be added time information, so the reader needs a real-time clock to record the natural time. PCF8563T produced by PHILIPS is an industrial class I2C bus low-power clock and calendar chip. It has four alarm function and timer function. The internal clock, oscillator, low-voltage detection, and two-wire I2C bus communication increase the reliability of the chip. SummaryIn this paper, the design of electron 2.45GHz Active RFID tags and reader have the properties of long transmission distance, high transmission speed, high-resolution card, high reliability, anti-static. And have a lot of practical features. The system use modular design, so different applications can require the use of different combination of the actual range of function modules. The hardware consults the requirements and standards of industrial production. This study not only has the significance of design, but also has more production value. It is not only the flexibility to facilitate the application and medical institutions in real-time positioning system for medical items, personnel management, can also be applied to a wide range of posts and telecommunications, and transportation of all kinds of application of radio frequency identification applications.更多还原