Research And Design Of Passive UHF RFID Tag Antenna

Internet of things (IOT) is an emerging strategic industry and has gotten great attention globally. As a popular technology of IOT, the Radio Frequency Identification (RFID) technology is also experiencing rapid development and widespread application. In compared with other RFID technologies, the ultra-high frequency (UHF) RFID technology appeal more concern with further reading distance, larger capacity and lower cost.This paper gives a detailed study of UHF RFID system on tag antenna design and performance measure methods based on antenna design knowledge and electromagnetic theory.Firstly, the thesis analyses the characteristics of UHF RFID system, and explores the antenna theory and main performance parameters. At the same time, this part also introduces the design methods, the impedance matching and measuring methods for tag antenna.Secondly, this thesis analyses the characteristics of the dipole tag antenna, focuses on the miniaturization of the dipole antenna and improves the antenna structure. A progressive meander-line dipole antenna with bars is designed, and the size of antenna is 40mmx36mm, and the frequency band of antenna is 840-965MHz, thus the antenna has the miniaturization and broadband characteristic. Meanwhile, the impedance of antenna is easy to adjust and the theoretical read range can reach 9m. The tag antenna has a good performance which satisfies the design requirements.Thirdly, the thesis explores the effect of the metallic environment on the tag antenna performance and shows the dipole tag antenna does not work in the metallic environment. Then, based on the common rectangular microstrip antenna, a low-profile anti-metal passive UHF RFID tag antenna is designed. This antenna is embedded with a pair of F-type slot. By using a short-circuited stub feed in the antenna plane, good complex impedance matching between the antenna and the tag chip can be obtained. The simulation results show that the proposed anti-metal tag antenna has good broadband characteristics (impedance bandwidth is 212MHz, return loss S11<-10dB) and good impedance matching in the UHF band (840 960MHz). Also, the proposed antenna has good radiation pattern and gain.Finally, these tag antennas which are designed in this paper are manufactured and the testing methods are summarized. Then, this paper tests the impedance of tag antenna by using vector network analyzer. The simulation results and actual measurement results are basically consistent. At last, the paper sets up the reading range test platform of the tag and completes the maximum reading distance test.