Study On The Metal Resistance Property Of UHF RFID Tags

Radio frequency identification(RFID)technology is an automatic identification technology that started in the 1990s and is gradually mature.It uses non-contact identification of target objects through the spatially coupled transmission characteristics of radio frequency signals.Two-way communication technology.It is widely used in access control,transportation,Warehousing and logistics,medical and other fields and industries.UHF(Ultra High Frequency)RFID tags are widely used in industrialized fields such as warehouse logistics and equipment management due to their faster information transmission efficiency and longer identification distance than ordinary tags.In the above application scenario,the tag antenna will inevitably contact metal objects,and the metal environment will interfere with the performance parameters of the RFID tag and cause the reading performance to decline,which is an important technical problem that hinders its popularity and wide application.In this paper,the effect mechanism of metal environment on the performance parameters of RFID tags is analyzed in detail,and the performance parameters of metal environment on tag antennas are analyzed in detail by adjusting the metal surface physical parameters such as metal plate size,metal plate and label distance,and metal internal electromagnetic parameters.Finally,based on the theoretical analysis of metal environmental impact,a high-gain anti-metal tag antenna that meets the requirements of metal environmental work is designed.First,this article introduces the working principle of UHF RFID system and the basic performance parameters of the antenna,and analyzes the impact of the physical parameters of the metal surface on the performance parameters of the tag antenna.Ansoft HFSS software was used to simulate and analyze the ALN-9640 tag.It was found that the input impedance,radiation pattern,antenna gain,and return loss of the ordinary tag antenna changed significantly on metal surfaces.When the distance between the metal and the tag increases,the power reflection coefficient and gain of the tag antenna increase significantly,and the effect of reading and writing voids on the metal surface gradually disappears.Through a large number of simulations,it is found that the antenna reaches the optimal working state when the tag and antenna distance is?/4..Changing the size of the metal plate has little effect on the antenna's input impedance,pattern,and resonance frequency,but as the size increases,the antenna gain will first increase and then decrease.Secondly,the influence of the metal's own electromagnetic parameters on the performance parameters of the label is analyzed.The calculation of Maxwell software combined with theoretical analysis shows that the relative permeability is an important factor affecting the electromagnetic loss of the antenna.The electromagnetic loss in the magnetic material metal is much larger than that of the non-magnetic metal,which shows the absorption of electromagnetic waves.Metal magnetism has no significant effect on the radiation pattern and input impedance of the tag antenna,but it has a more severe suppression effect on the antenna gain.As the permeability loss tan?increases from 0 to 0.5,the gain of the magnetic metal surface antenna decreases from 2.41dB to 1.72dB.Based on the feature that increasing the radiation impedance will increase the tag antenna gain,a high-gain anti-metal tag antenna that meets the miniaturization of the antenna is finally designed.An RF-4 material with a thickness of h=3 mm was used as the dielectric substrate.Simulation analysis performed by Ansoft HFSS software determined the optimized antenna size structure to achieve impedance matching between the tag antenna and chip(Z_C=27-j201,unit?).The working parameters of the antenna with different distances from the metal,different areas of the metal,and different metals are analyzed,and the simulation analysis is verified through experiments.The maximum recognition distance is above 5m,which meets the tags in the metal environment.Higher requirements for metal resistance and identification.The new type of anti-metal tag designed this time has low cost and simple manufacturing process,which is helpful for the mass production of tag applications.The high gain of the tag antenna can increase the reading distance of the tag,making it better to meet different metal environments The work needs to expand the application range of RFID tags.