UHF RFID Reader Circuit Design

Radio frequency identification technology as the most potential for development ofan information management technology in the21st century, it is a good solution to solveto the defects of the bar code, such as less information of the bar code, not be multi-tagreading, read shortly distance. Because of complicated and high price，large-scaleapplication of RFID to logistics management relative to the bar code does not have aprice advantage, so the RFID readers with a low-cost, low-power will be mainly tosolve the technical difficulties in the future.RFID system consists of three components: tags, readers, host. Tag storage objectinformation, the reader reads the tag information stored and transmitted it to the host,the host is responsible for management of the information. According to the RFIDtechnology standard system: ISO/EPC18000(International Organization for Standard-ization), the operating frequency of RFID can be divided into of13.56MHz,433.92MHz,860MHz~950MHz,2.54GHz.The ultra-high frequency (UHF),from860MHz to950MHz,is the most widelyapplied to RFID readers, as the core of the RFID technology, the RF performance of theRFID reader will greatly affect the read performance. According to the technicalstandard of ISO/EPC18000-6C (Gen2) UHF RFID reader is the same frequency intransceiver, So transceiver channel requires as possible as high isolation and for therequirements of smaller, single-antenna mode handheld reader, which will greatlyworsen the isolation between the receiver and transmitter. Based on this point, UHFRFID reader RF front-end circuit is designed, the main work is the adaptive carriercancellation technology to improve the isolation of the transceiver channel to enhancethe reader’s read performance. The main work is divided into three parts.1, the designof transceiver circuit. The transceiver system module is designed by using Phychipscompanies PR9000as the master chip.2, the design of carrier offset circuit in receptionchannel. The carrier which is accessed from the isolation port of the directional coupleris adjusted by the multiplexer carrier amplitude modulation and phase shift circuit toachieve the purpose of receiving channels carrier offset. adaptive detection and control circuit design, Atmel’s AT89C5115microcontroller as the master chip to achievereal-time detection of receive channel carrier and the carrier offset process real-timecontrol.3, Design programming, according to the ISO/EPC18000-6C (Gen2) technicalstandards and regulations, the preparation of the reader and carrier offset control circuitprogram.