Study On The Mutual Coupling Effect Of UHF RFID System In Label-Intensive Environment

With the maturity of the Internet of Things(IoT),radio frequency identification(RFID)technology,one of its core technologies,is more widely used in various fields of economic and social development.However,due to the increasingly complex application environment of RFID systems,its deployment has become more and more Intensive.The mutual coupling between dense tags can cause many mutual coupling effects on the RFID system,such as a decrease in system recognition rate,a shift in operating frequency,a decrease in tag antenna gain,and an increase in tag activation threshold.Studying the above problems,this has important guiding significance for RFID system performance research,label and reader design,and dense label placement in dense environments.Firstly,the article briefly introduces the basic electromagnetic field theory in the field of RFID antennas from Maxwell's equations,and theoretically analyzes the antenna electromagnetic field division of the electric small loop size antenna and the electric large loop size antenna in the RFID system.Aiming at the mature working mode of RFID system,the working principle of inductively coupled and electromagnetic backscatter coupled RFID system is briefly introduced.Secondly,based on the HF RFID system,the electromagnetic field fading around the 13.56 MHz antenna coil is analyzed,and the electromagnetic field distribution between two adjacent dense tags is given.An inductive coupling matrix of dense label system is proposed.The eigenvalues of the inductive coupling matrix are extracted and substituted into the Thomson formula to estimate the system frequency.The experimental results show that the proposed method is more accurate than the full coupling method and the superposition method.Thirdly,based on the transformer model,the mutual impedance expression between dense tags of UHF RFID near-field system is derived from the perspective of wireless energy transmission,and the near-field frequency offset problem of UHF RFID is studied from the perspective of environmental factors affecting the mutual impedance between two tags.The test results show that when the label spacing is d<30mm,the derived mutual impedance expression is applied to the frequency offset calculation error range 1.6MHz~7.3MHz.The research results provide a reference for the mutual coupling effect between UHF RFID near-field tags based on mutual impedance estimation between tags.Finally,based on the UHF RFID far field system,a small interval dense label HFSS simulation model and a large interval dense label experimental test platform were established from the dense label spacing d ??2? and d(29)?2?.The interference label was found to be in the working label induction.The mutual coupling effect of the UHF RFID far field system in the field area and the radiated far field area is analyzed.The influence of mutual coupling effect on the gain,directivity coefficient and minimum transmit power of the working tag antenna is analyzed.