Research On New Passive Tags In Radio Frequency Identification And Sensing System

Radio frequency identification(Radio Frequency Identification,RFID)and sensing technology are the key technologies of the Internet of Things.The tag is an indispensable information carrier in the radio frequency identification and sensing system.Compared with other types of tags,passive tags do not contain batteries,so the cost is low,the structure is simple and the service life is long,but there are also defects such as limited functions.Therefore,it is of great significance for the development of radio frequency identification and sensing technology to study the theoretical basis,to explore the performance improvement methods of passive tags,and to realize low-cost,miniaturized and flexible passive tags in different application scenarios.In this paper,the new passive tags are studied from three aspects:the study of the theoretical model of passive tags,the design of liquid sensing tags,and the exploration of flexible passive tags.First,for the passive chipless RFID tags based on high impedance surface(HIS)structure,a compact and scalable physical model is proposed and validated.Based on the physical model,the lumped circuit parameters of the tag and the analytical formula of Radar Cross Section(RCS)are derived.It is worth mentioning that the lumped parameters and RCS values directly depend on the inherent physical size of the tag itself,which endures these parameters with physical meaning.Using this method and process,you can quickly and accurately calculate the resonance frequency,reflection coefficient,input impedance,RCS,and other parameters of this and other similar HIS structures.Secondly,a passive and chipless RFID tag for wireless liquid sensing is proposed.The chipless tag is loaded with a slot on the metal surface of the quarter-mode substrate integrated waveguide resonator,and some holes are provided in the high electric field strength area for loading the liquid sample.Liquid samples with different dielectric constants shift the tag resonance frequency.The frequency shift corresponds to RCS one by one,and is used to distinguish several specific liquids.Based on the analysis and design of the tag,a circular polarization transceiver system is built and two liquid materials are measured to verify the effectiveness of the compact chipless tag.Compared with existing similar tags,the tag has the advantages of wireless sensing,long service life,simple processing,low cost,flexible placement,and attachment to the surface of objects including metals.Finally,in order to meet the need for flexibility in radio frequency identification and sensing tags,spoof surface plasmons is further explored and a variety of artificial surface plasmon components are designed,including a broadband differential balun,multi-mode resonators and filters.These devices can be applied to radio frequency identification and sensing systems,and the multi-mode resonances are expected to be used to control the coding bits of flexible tags.