Design Of UHF RFID Reader

RFID (Radio Frequency Identification) technology is characterized by non-contact automatic identification, used to automatically identify target and access to relevant data through RF signals. The recognition process is without human intervention, and both multi-objective and moving target identification can be achieved. This paper designed an UHF RFID reader based on the ISO/IEC 18000-6C standard.Hardware design consists of baseband and RF parts. The Single-chip Microcomputer C8051F120 is used to realize the function of baseband part, including the coding and the decoding of signals, data processing, communication with application software of the computer and execute the commands from the application system software, RF part of reader includes the carrier signal synthesis module, ASK modulation module, power amplifier module, signal isolation devices, filter circuit, demodulation circuit. The circulator is used to separate forward transmitting signal and backward receiving signal. The receiver front-end uses homodyne receiver structure. This paper has made the detailed introduction to circulator's principle and analyzed the advantages and disadvantages of homodyne receiver structure.The system software adopts Top-down design procedure and divides the source codes into several modules, such as sending module, receiving module, main control module and CRC module. The program has been implement using languish C. The paper introduces the algorithm of PIE encoding, FM0 encoding, CRC encoding, sending and receiving of the single-chip, multi-tag reading and its implementation.Finally, test the reader, which realize the basic function of ISO/IEC18000-6C standard. The reader can read and write tags in 10 meters and display the EPC code of these tags on upper computer at the same time. The frequency synthesizer ADF4111 is used with a VCO (Voltage control oscillator) to produce the local oscillation signal (915MHz) for ASK modulation, which improves the stability of the system.