Research On Key Technologies Of The Antennas In RFID System

With the rapid development of the Internet of Things?IoT?in recent years,the radio frequency identification?RFID?technology has been widely applied to many fields.The property demands of RFID antenna miniaturization,high-gain,wideband,circular polarization and so on are becoming more and more prominent.The tag antenna for metal surface and reader antenna in ultra-high frequency?UHF?and microwave frequency?MW?are researched and designed in this dissertation.Its content is listed as follow:1.Design of the UHF band tag antennas for metal surface.Here,two tag antennas are designed in this paper,which are compact structure with broadband and ultra-thin profile with high-gain,respectively.The former adopts the double-layers coupling structure and similar-dipole radiation patch whose impedance bandwidth can cover the UHF bands like the European standard,the American standard,the Chinese standard and the Japanese standard.Its measurement result shows the recognition distance reaches 4 meters.The latter utilizes open slots structure and its depth is0.8mm.Meanwhile,the maximum identification distance is 4.5m in free space while the distance is 6.8m as it is close to the metal surface.2.Research on portable reader antenna.The dissertation presents a novel miniaturization high-gain antenna based on verified Quasi-Yagi antenna whose size is about?₀/3×?₀/3??₀ is the wavelength at center frequency?and its measured gain achieves 6.8dBi.Then,two broadband antennas in microwave band are proposed based on the antenna mentioned above.The impedance bandwidths of them are2.27-3.35GHz?1.08GHz?and 2.14-3.3GHz?1.16GHz?,respectively.These antennas can operated in several wireless frequencies range and exhibit good performances near the human body.Finally,a new compact antenna for 2.45GHz and 5.8GHz is designed by using?balun feeding and two levels radiation dipoles,which possesses good directivity in these frequency bands.3.Development of the fixed reader.This dissertation describes a novel broadband circular polarization antenna applied in 2.45GHz fixed reader with single-feeding planar structure.Its axial ratio and impedance bandwidth are 40.7%?2-2.95GHz?and62.1%?1.61-3.06GHz?,respectively.The operation band covers the multiple wireless bands with good electric performance.