低频射频识别技术分析-机械电子工程专业论文.docxVIP

AbstractIII Abstract III Abstract As one of the automatic identification technology，radio frequency identification (RFID) is becoming more and more important and common in people’s life recently. It could effectively abridge the human resource in many industries, thus could save a lot of expenditure for many companies. The low frequency RFID could be widely used in stock farming system, non-key access control system, auto-parking system, and underground pipe detection etc. So it has a very bright future in the market. The whole scheme for LF RFID system is proposed. The MCU produces a square wave signal with a frequency of 125 KHz. Then the signal is driven up and used to control four MOSFETs. The four MOSFETs form an inverter, which could be used as a power amplifier. The inverter could produce a signal with amplitude of 24 volt, which is then sent out by a coil antenna. The receiving circuit adopt three-stage amplifier to enlarge the receiving signal. The system works by two steps. In the first step, the LF RFID system sends signals to the tag. Then the reader stop sending signals and the reader antenna discharge before receiving the backscattered signal. After the coil antenna finishes the discharge progress, the RFID reader switch to the second step, receiving signals from the tag. The tag is charged at the first stage and then discharge in the second stage. What’s more, the theory of LF coil antenna is studied in this work, and reader coil antenna and tag coil antenna are designed, fabricated, and designed. The inductances of them are 48.1uH and 3.2 mH respectively. The circle tag antenna has an inner diameter of 42.6mm and outer diameter of 88.6mm. In the end, the PCB prototype are presented and fabricated on FR4 substrate. The test results are demonstrated, including the output signal of MCU, the input and output signal of the inverter, the receiving signal, and the tag induced wave pattern.To be concluded, the LF RFID system is made out successfully. Keyword