Design And Investigaion Of Novel UHF Metal-mountable RFID Tag Antenna

Ultra High Frequency(UHF)Radio Frequency Identification(RFID)has the advantages of long reading distance and large data transmission rate and is widely used in logistics,Internet of Things,retail and other fields.With the continuous development of UHF RFID technology,RFID technology is inevitably applied to various fields.In some applications,RFID tags need to be attached to the surface of metal objects for use.When a traditional dipole-like RFID tag is applied to metal surface,its impedance matching and radiation characteristics will change,resulting in poor RFID tag performance and even failure to work properly.In order to solve the problem when RFID tags are applied to the surface of metal objects,vertical loop antennas and microstrip antennas are adopted as prototypes to design metal-mountable tag antenna in this thesis.The inset-feed structure and E-shaped patch are added to the antenna structure to achieve tag antenna input impedance adjustment and the performance of metal-mountable RFID tags in metal environment is studied.The research content and innovative summary of this thesis are as follows:For the North American UHF RFID frequency band(902 MHz-928 MHz),a metal-mountable tag antenna is designed based on the vertical loop antenna structure.The tag antenna mainly includes an inset-feed structure and a rectangular slot structure.The introduction of the inset-feed structure and a rectangular slot structure can achieve the miniaturization of the tag antenna and the changing of the input impedance of the tag antenna.The final size of the metal-mountable tag is 50 mm ×20 mm × 0.9 mm.The actual measured maximum reading distance is 4.3 m at 910 MHz.Its half-power bandwidth is 55 MHz,which covers the North American UHF RFID frequency band.The reading performance is relatively stable on metal plates of different sizes and the surfaces of different metal objects,and always maintains a high level.For the UHF RFID frequency band(920 MHz-925 MHz)of China,a metal-mountable tag antenna based on E-shaped patch is designed.The tag antenna mainly includes an E-shaped patch and a short-circuited stub structure.The tag antenna can be miniaturized by designing the patch as E shape.The short-circuited stub structure makes the input impedance of the metal-mountable tag antenna adjustable within a wide range.The final size of the metal-mountable tag is 54 mm ×30 mm × 1 mm.The measured maximum reading distance of the tag is 7.3 m at 918 MHz,and its half-power bandwidth is 16 MHz,which covers UHF RFID frequency band of China.When tested on the metal plates of different sizes and the surfaces of different metal objects,the reading performance fluctuates little,always has a large reading distance,and the working frequency is hardly shifted.The two metal-mountable tag antennas adopt new structures to achieve the miniaturization and low-profile design of the antenna and the easy adjustment of the input impedance of the tag antenna.Finally,the miniaturization and low profile characteristics are achieved.At the same time,the reading performance of the tag has good stability in different metal application scenarios.