Research Of Some Key Technologies In RFID Systems

Wireless radio frequency identification (RFID) system is a kind of advanced technology to identify goods and human identity intelligently and automatically. It may improve the efficiency and reliability of merchandise management, logistic control and security check of people. RFID system is mainly composed of two parts, tag and target. In this paper, the design of hardware circuits and the idea of software design of the RFID system, which works at 13.56MHz according to the theory of inductance coupling, are presented.First of all, the composition and classification of RFID systems are simply introduced in this paper. And then the theory of magnetic field i.e. the physical working foundation of the system is particularly discussed from the point of view of RFID systems. The whole structure and the design of the key circuits of the hardware system researched are analyzed particularly afterwards. ASK modulation is adopted to transmit data from target to tag, while load modulation adopted from tag to target. 2SC1945 and class C power amplifer are adopted in the output circuit of the target to improve the output power and efficiency. Separated components are adopted to design the tag circuits. Tag rectifies the received signal and provides power supply V_CC for microcontroller to work. 16-bit microcontroller MSP430 is adopted in the tag to reduce the power consumption and increase working distance. Finally, the antenna, ASK modulation, power supply of the tag, load impedance modulation, demodulation, power supply sensor and HF power amplifier were realized.In the software part, the working flow of the system is introduced first. And then the two key technologies, Cyclic Redundancy Check (CRC) method and Anti-Collision method are presented.There are innovations in the method of tag design, the selection of microcontroller, the design of HF power amplifier, load modulation and demodulation circuits in this paper.In the end, the conclusion is made. Those worth further research and optimization are put forward, and the subject is prospected.