Design And Implementation Of Multi-antenna RFID Long-range System Based On FPGA

In recent years,the country has continuously increased its support for the development of Io T technology,Radio Frequency Identification(RFID),as one of the core technologies of Io T,has rapidly developed and expanded into new application fields.RFID technology is based on inductance or electromagnetic coupling to achieve non-contact reading and writing,with the advantages of high efficiency,automation and multi-target fast identification,which has been widely used in the fields of item recognition,data collection,and logistics management.The data exchange of RFID systems is achieved through wireless electromagnetic wave transmission that relies on antenna coupling.However,there are signal attenuation,path loss and other phenomena in the space transmission process of electromagnetic waves,especially when the UHF RFID system identifies the metal material medium,it will lead to multipath propagation and signal interference.When encountering the water medium,it is easy to appear attenuation and decoupling,which seriously affects the read-write communication distance of the RFID system,reducing the identification effectiveness and reliability of the RFID system.This dissertation focuses on how to achieve long-distance reading and writing communication in RFID systems,focusing on the design of reader software and hardware,relay antennas,and other aspects.A high-frequency RFID system with a working frequency of 13.56 MHz has been designed.Firstly,based on the characteristics of the RFID system and the ISO/IEC15693 standard,determine the structure and working mechanism of the high-frequency RFID system.The baseband signal generation and reception signal processing of RFID systems are achieved using the "Field Programmable Gate Array(FPGA)+Transceiver Circuit" scheme.The emphasis is put on amplitude modulation(ASK),pulse position coding modulation,data frame structure,cyclic redundancy check(CRC)and anti-collision processing technology based on time division multiple access(TDMA)in RFID communication protocol.Secondly,a relay antenna design was introduced.Establish a dual antenna coupling system without a relay antenna and a three-antenna coupling system with a relay antenna,and theoretically derive the factors that affect the transmission efficiency of the antenna coupling system.Establish an equivalent circuit diagram using Advanced Design System(ADS)software to analyze the transmission loss S21 parameter.The antennas resonate at a frequency of 13.56 MHz,and compare and analyze the transmission efficiency and loss of the two antenna coupling systems.Simulation data shows that introducing relay antennas in RFID systems can effectively reduce transmission losses and improve the efficiency of wireless electromagnetic wave transmission.Then,based on the idea of radio circuit design,the hardware circuit of high frequency RFID reader is designed,including digital baseband circuit,RF transmitting circuit,antenna switching circuit,superheterodyne receiver circuit and power circuit.And the implementation methods of logic control,data processing,and transmission protocol were determined.Corresponding Verilog code was written on the FPGA chip,and timing simulation verification was conducted using Model Sim simulation tool to simulate the data transmission process.Finally,establish an RFID system testing environment to test the signals at key positions of the digital baseband circuit,RF transmission circuit,and receiver circuit of the reader,and verify the correctness of the hardware platform and software design.Establish an RFID testing system for quantitative and qualitative analysis,and study the impact of relay antennas on receiving antenna voltage and the farthest reading and writing distance of tags.The experiment shows that the introduction of relay antenna design in the RFID system effectively reduces transmission loss,improves wireless electromagnetic wave strength and transmission efficiency,and achieves long-distance reading and writing communication in the RFID system,achieving the expected effect.