Research And Application Of RFID Detection Technology In A Closed Environment With Strong Reflection

With the continuous development of modern information technology,the application of RFID technology has become increasingly extensive.Among them,the market share in the warehouse management field is increasing.The warehouse management field is a typical RFID application field which is in a closed environment with strong reflection.In such an environment,the problem of leakage reading and misreading of the tags is more serious than other application scenarios.Taking the item management cabinet as an example,increasing reader’s power transmission causes misreading of the tags in the next cabinet.If the reader’s transmission power is reduced,it causes leakage reading of the tags in this cabinet.This thesis mainly focuses on the problem of tag leakage reading.The problem of tag misreading can be effectively solved by shielding cabinet and the upper computer algorithm.The specific work of this thesis is as follows:(1)The complete link loss model of RFID system in closed environment with strong reflection is established.Aiming at the application scenarios of multi-tag RFID in a closed and strong reflection environment,this thesis analyzes the influence of the multipath,mutual coupling between the tags and self-jammer signal on the link loss of the RFID system.The multipath loss factor,the power transmission coefficient,the modulation loss factor and self-jammer signal are introduced to establish a loss model of forward and reverse links.The self-jammer signal is introduced into the link loss model for the first time.By analyzing the circuit,this thesis provides the correct mutual impedance formula.Then,the general formulas for power transmission coefficient and the modulation loss factor incorporating the mutual coupling effect between the tags are derived.The relationship curves of each of them and the tag spacing are drawn,which are consistency with the results of the experiments.(2)This thesis analyzes the generation mechanism of the recognition blind zone,and two solutions are proposed:main and auxiliary channels,and the adaptive self-jammer cancellation.By analyzing the link loss model,this thesis explained that the multipath propagation,the mutual tag coupling between the tags and self-jammer signals are the main reasons for the recognition blind zone.According to the idea of enhancing the energy acquisition of the forward link and improving the signal-to-noise ratio of the reverse link,blind zone elimination scheme based on the main and auxiliary channels and the adaptive self-jammer cancellation scheme are proposed respectively.On the basis of theory and simulation analysis,the blind zone cancellation circuit based on the main and auxiliary channels is designed.The optimal control strategy of the auxiliary channels and the optimal layout of the main and auxiliary antennas are given.On the basis of analyzing the principle,an active self-jammer cancellation circuit is designed.Through the improved Powell optimal search algorithm,the adaptive adjustment of circuit parameters is realized to make the circuit work in the optimal self-jammer suppression state.(3)A multi-area distributed detection system for items in the cabinets is designed and built which is composed of the main cabinet control board,the sub-cabinet control board and the host computer.The blind zone elimination schemes of the RFID system proposed in this thesis is tested and verified.The test results show that compared with the reader using R2000 chip alone,the blind zone elimination scheme based on the main and auxiliary channels can improve the tag recognition rate from 86.43%to 95.71%.In the RFID frequency band between 840 MHz and 960 MHz,the adaptive self-jammer cancellation scheme can automatically adjust the parameters in about approximately 3.9ms.Compared with R2000 chip,it can improve the suppression rate from 23dB to 37dB,and improve the tag recognition rate from 62.14%to 83.71%.Compared with R2000 reader,the detection system of the items in the cabinet which use both of the above schemes proposed in this thesis can increase error-free rate of the tags from 81%to 94%,and the research work in this thesis can solve the problem of tag leakage reading in a closed environment with strong reflection.