| Internet of Things,as one of the three application scenarios of the "5G era",it has broad market prospects.As the core technology of the Internet of Things,radio frequency identification(RFID)technology will play a crucial role.Ordinary RFID tags contain chips,which can’t compete with bar codes because of their high cost.Therefore,the research of low-cost chipless RFID tags is of great significance and is one of the focuses of modern RFID technology research.This paper mainly focuses on the design and research of a chipless RFID tag structure with compact structure,large code capacity and strong environment adaptability.(1)According to the radio frequency identification theory and the analysis of resonance characteristics of different resonant units,three chipless RFID direction insensitive tags are designed: they are "I" shaped patch resonator tag with a coding capacity of 9 bits,the 15 bits tag of 1/4-ring patch resonator and the 16-bit tag of equilateral triangular slot resonator respectively.Three kinds of tags were simulated and verified in FEKO simulation software.The effects of incident direction,polarization of the incident wave,and the position of the observation point on the radar cross section(RCS)of the tag were mainly analyzed,and the tag’s code capacity scalability was studied without increasing the tag size.In order to increase the reading distance of tags,based on the radio frequency characteristic of frequency selective surface(FSS),a periodic array tag structure was designed based on the tag of equilateral triangular slot resonator to obtain a larger RCS and achieve long-distance reading of tags.(2)Using the single-polarization characteristics of the "I" resonator and the 1/4ring resonator,based on the designs of their direction-insensitive tags,the polarization diversity and polarization multiplexing,two kinds of RFID dual-polarization tags with double code capacity and a 50% increase in spectrum utilization were further designed respectively: One is an 18-bit tag of "I" shaped patch resonator,and the other is a 30-bit tag of 1/4-ring patch resonator.Using the dual polarization coding idea,the results of dual polarization coding are given.(3)The five kinds of tags were compared and summarized.Finally,using the pole expansion method and the matrix beam algorithm to extract the poles and residues of different tags,and completed the detection and recognition of the tags. |
