The Research And Design Of The Tag That Mountable On The Metallic Objects In UHF-RFID System

UHF-RFID(Ultra High Frequency Radio Frequency Identification)systems has its own unique advantages,such as the high data transferring rate and the long identifying distance.Consequently,it has gained great interest from many industries,including logistics,transportation and the Internet of Things.RFID systems need to identify the tags on the metal surfaces for some application scenarios.However,when a common dipole tag antenna is placed on the surface of the metallic objects,the performance of the antenna will deteriorate sharply and the reading range of the tag will be rapidly shortened.And even,the tag will not be identified.In order to make the RFID tag operate well on the metallic surface,this paper first studied the theoretical knowledge of the tag antenna,and then two kinds of tag antennas were designed and implemented for the UHF-RFID system in the metallic environment.Finally,the two kinds of tags were measured.The tag antennas maintain a relatively good consistency on the simulated performance and the experimental performance.The innovations and work contents of the paper are summarized as follow:(1)The first anti-metal tag antenna is designed for North American UHF band 902MHz?928MHz.It is based on microstrip patch structure and applies an inset microstrip feeding structure.The antenna consists of a shorting stub line to easily adjust the antenna reactance and a directly coupled patch to increase the bandwidth of the antenna.The impedance matching of the tag antenna and the tag chip at the center frequency is very good.The 3dB impedance bandwidth covers North American UHF band.The measurement reading range of the tag is 10.2m in the direction of the maximum radiation.(2)The second anti-metal tag antenna is designed for Chinese UHF band 920MHz?925MHz.It is based on planar Inverted-F antenna(PIFA)structure and applies a coplanar waveguide feeding structure to easily integrate with tag chips.It consists of a U-slot and several shorting via holes to improve the bandwidth of the antenna.The impedance matching of the tag antenna and the tag chip at the center frequency is relatively good.The 3dB impedance bandwidth covers Chinese UHF band.The measurement reading range of the tag is 8.21m in the direction of the maximum radiation.