Research On RFID Perception Of Complex Confined Space For Internet Of Things

Internet of Things(IoT)covers information perception,network transmission,storage,analysis and intelligent applications process.The perception layer is the foundation and main data source of the IoT,among them,radio frequency identification technology is the key technology,the efficiency of radio frequency perception directly affects the quality of information interaction.Complex confined space is one of the main scenarios for information exchange and transmission of IoT.The confined area has small space and irregular shape,and the electromagnetic propagation environment is relatively complex.Research for the electromagnetic sensing characteristics in the constrained space can effectively improve the efficiencyof IoT information interaction.This thesis oriented to the needs of IoT applications,mainly analyzes the effects of electromagnetic characteristics in complex confined spaces based on geometric features,media types,and multi-source interference.The main contents include:Firstly,based on the geometric characteristics of confined space,the propagation path loss theory,geometric ray tracingtheory and uniform diffraction theory,path loss model based on high loss factor is proposed.The effects of direct,refraction,diffraction and scattering on electromagnetic path loss are discussed.Based on geometric characteristics,the propagation path of electromagnetic waves is divided into different geometric regions,and the path loss models of multi-class scenes are discussed.The influence of scattered signals caused by rough ground on receiving signals is also considered in the research process.The effect of factors such as antenna operating frequency,antenna height,RFID tag position and space geometry on path loss is discussed.The results show that in order to reduce the path loss,the optimal position for RFID tag placement is the upper half of the device.The experimental and simulation results optimize the radio frequency sensor wireless sensing paths and the efficiency of RFID,which realizing the dynamic management of equipment.Secondly,the propagation mechanism of electromagnetic waves in multi-media environment is studied.Based on the ray tracing method in the confined complex environment,multipath transmission characteristics were simulated and analyzed.The effects of wood medium,metal medium,glass and plastic medium on electromagnetic wave propagation performance were studied.The distribution of received power,delay distribution,mean square delay spread and other parameters under line-of-sight propagation and non-line-of-sight propagation were analyzed.The analysis results provide a basis for the deployment of RFID tags in a confined environment,and provide an effective theoretical and practical basis for link budget,coverage prediction,electromagnetic simulation and interference analysis of electromagnetic sensing.Through the study of the propagation path,each path to the receiving point can be accurately analyzed,which greatly improves the efficiency of IoT information interaction.Thirdly,the theoretical analysis and actual test of multi-tag interface in complex environment are carried out.Based on the transformer model,the inductive coupling mutual impedance expression forinduction near-field region of densely placed UHF RFID is derived from the perspective of wireless energy transmission.The double-tag is taken as an example to extract the coupling coefficient between dense tags,and the mutual impedance value between the tags is introduced into the working frequency offset calculation process;the internal interference between dense tag nodes in the confined space is analyzed.Based on the principle of multi-source signal S transform,the electromagnetic environment time,frequency and energy occupancy rate are evaluated.Through the simulation of the same-frequency interference signal and noise signal,the subjective complexity and objective complexity based on multi-dimensional F norm are given.The study of multi-tag interference mechanism effectively evaluates the conflicts in the process of electromagnetic sensing and improves the efficiency of tag-aware recognition.Finally,RFID is applied to the equipment management process.The technical requirements and implementation methods of multi-tag equipment management are analyzed.For the identification of small-size tools,the inductively coupled Impinj J41 ultra-wideband ring tag is used for simulation,and three typical confined spaces are constructed for extracting thecoupling features.The relative position of the tag,the stacking method,and the influence of the attached medium on the working frequency shift of the tag were studied.The influence of the metal medium on the sensing performance of the tag antenna was analyzed.Finally,the influence of multi-tag interference on the minimum transmit power of the reader antenna is analyzed.The results show that in the actual application process,the tag spacing and the angle should be as large as possible to reduce the transmit power of the reader.The research results are important for asset management under dense tag environments.