Design And Implementation Of UHF RFID Reader

Radio Frequency Identification(RFID),as a contactless and low-cost automated identification technology,is widely used in the Internet of Things(IoT).Physical objects labeled by electronic tags can connect with IoT to identify themselves and collect information through RFID technology.With the improvement of RFID system functions,the requirements for data transmission rate and data traffic are also gradually improved,so RFID readers with better functions and performance are in greate demand.However,lots of cheap Ultrahigh Frequency(UHF)RFID readers in the domestic market only have the function of reading,without writing data,and the communication distance is short.Besides,some UHF RFID readers of high performance are expensive,thus obstruct the promotion of RFID technology.For the problems above,the thesis designs and implements an UHF RFID reader based on ISO 18000-6B/C protocol to realize the function of reading and writing,which can also meet the requirement of low cost,long communication distance,fast identification and stable performance.At the same time,novel anti-collision mechanisms of RFID systems are proposed for static and dynamic RFID scenes respectively as the solutions to data collision when readers identify multiple tags.The main contributions of the thesis are summarized as follows:(1)The thesis researches the key technology of RFID systems and introduces its composition,basic principles,common coding and modulation methods.Also,the thesis briefly introduces the data collision challenges faced by RFID systems.(2)The modular design concept is used to design and implement the hardware system of UHF RFID reader.The baseband control module takes STM32F103ZET6 Micro Controller Unit(MCU)as the core and the data interfaces module includes J-TAG and USB to UART circuits.Besides,the radio frequency transceiver is composed of KLM900 and R2000 integrated chips.Also,the hardware system contains the power module.(3)The software design of the system is achieved,including commonly used instruction planning and definition of format for data frame,design of MCU software and communication unit of upper computer.(4)The thesis researches the non-deterministic anti-collision algorithms based on ALOHA.Considering that the Enhanced Dynamic Framed Slotted ALOHA(EDFSA)algorithm is lack of accuracy in estimating the number of tags and flexibility in adjusting the frame size and the number of tag groups,a modified algorithm(EDFSAI)is proposed to solve these problems for static RFID systems.For the problem that in traditional anti-collision algorithms,the impact of moving tags on tag quantity estimation is not taken into account in dynamic RFID systems,an improved algorithm based on dynamic RFID systems(EDFSA-DS)is proposed.The simulation results show that both of the two algorithms can improve the recognition efficiency of the systems.(5)A test system is built up to accomplish the basic function tests and performance tests.The results show that the reader can complete the reading,writing and other operation quickly and accurately.What's more,the reader is in excellent working status with a maximum communication distance of 15 meters,which meets the design requirements.