Engineering Design Of RFID Tag Antenna

As one of key technologies of the Internet of Things,Radio frequency identification(RFID)technology,has a wide application prospect with the advent of the Internet of Things era.It also puts forward more and more requirements about its techonologies.As a device for transmitting and receiving radio frequency signals,the high-level of the system and the products are connected by the RFID tag antenna in the system.Its performance affects the reading distance and accuracy of the system,which is a vital part of the system.It is difficult to ensure a good impedance match while making the antenna small for the connected chip has complex impedance characteristics.This thesis has carried out on the technical research of miniaturization and high gain of the electronic tag antenna applied in engineering practice.The main content is presented as follow:1.The design of the meandering tag antenna has been studied,which is used for the study the influence of various parameters.For the antenna,the length of both the bent part and the horizontal part affects its impedance value as well as the resonant frequency.This thesis studies the influence of antenna design parameters on antenna impedance and power transmission coefficient.Comparing the influence of various structural parameters on transmission coefficient and summarizing the parameters sensitive to the real part of the impedance,the parameters sensitive to the imaginary part of the impedance,as well as the overall frequency sensitive parameters,the design method of bending antenna is given.Subsequently,the antenna is meandered and the conjugate matched with Higgs-3 chip impedance is realized according to the law of the characteristics of structural parameters.The design antenna is in the 915 MHz frequency range,with the power transmission coefficient is 0.9899 and the gain is 1.31 d Bi.The results show that the method is effective and provides a new method for solving the impedance matching of the antenna and the chip.2.The impedance matching technology of bent antenna is studied.On the basis of bent antenna,a smaller horizontal omnidirectional tag antenna is designed by adding T-type matching network.When the antenna is bent to adjust the impedance,it is easy to increase the size of the antenna due to the length change of the bent arm.The change of the parameters of the T-type matching network has a far greater effect on the imaginary part of the antenna impedance than the real part.The study found that the T-type matching network in the bent antenna structure can make the antenna miniaturized and reduce the difficulty of impedance matching.The results of model show that the size of the tag antenna designed by the T-type matching network is reduced by 33.3%,and its performance is improved in many aspects.For example,the power transmission coefficient also reaches 0.9993,the gain is 1.78 d Bi which has an increase of 0.47 d B.The results show that the addition of T-type matching network not only can achieve miniaturization of the antenna but also reduces the difficulty of impedance matching between antenna and chip.3.Two tag antennas conformal to the metal ring structure are designed according to the needs of application scenarios.Considering that the reflection of the metal floor will deteriorate the performance of the dipole antenna,the coupling stubs are introduced between the metal floor and the antenna.The stubs together with the bent stubs of the bent dipole,the input impedance of the antenna can be improved.In the frequency range of 920-925 MHz,the research results show that the power transmission coefficient of antenna can reach up to 0.96,and the antenna gain is 0.61 d Bi,which meets the application requirements of actual engineering.Moreover,a high-dielectric constant microstrip patch antenna is used to realize the conformal tag antenna design.In addition to the metal floor,the ring-shaped metal structure that participates in the antenna conformal is relatively large.By adjusting the length of the radiating patch of the antenna and the position of the feed point of the coaxial probe,the conformal microstrip patch antenna is designed.The antenna bandwidth covers917MHz-932 MHz,and the antenna gain is 1.5 d Bi.Finally,the content of the full text is summarized and the direction of further research is determined.