Design On The UHF Band RFID Reader Antenna Based On Fractal Structure And Its Experimental Research

Radio Frequency Identification(RFID)is an important,non-contact wireless communication technology that realizes the transmission of information through the propagation of electromagnetic waves in space.Antenna is the bridge of wireless communication in RFID system.The progress of antenna technology will promote the development of wireless communication.This paper studies and designs three RFID reader antennas working in the UHF band,as follows:Firstly,this paper introduces the development requirements of RFID reader antenna,and reviews the research status of miniaturization and circular polarization of RFID reader antenna at home and abroad.Then introduce some related design theoretical foundations of antenna,including electrical parameters,analysis methods,and design process of antenna.Secondly,based on the theory of microstrip antenna,the miniaturization technology of antenna is emphatically studied,and a miniaturized UHF band RFID reader antenna based on fractal structure is designed.The antenna uses the Minkowski fractal and the Koch fractal together to achieve miniaturization of the antenna and improve the matching degree of the antenna to some extent.The design of antenna is supplemented by slotting technology,which further reduces size of the antenna and meets the design goal of miniaturization of the antenna.Finally,according to the circular polarization design theory of microstrip antenna,two circular polarization RFID reader antennas based on fractal structure are designed and fabricated.The design of the first antenna uses second-order Minkowski fractal and antenna loading technology to realize miniaturization.On this basis,a perturbation element is introduced to separate the degenerate modes of the antenna,so as to realize circular polarization of the antenna.The design method of the second antenna is similar to that of the first one.The miniaturization method is the same,but construction method of the circular polarization perturbation elements is different.It uses the deformed second-order Minkowski fractal to form perturbation,realizing the circular polarization of the antenna.The innovative variation of fractal makes reflection coefficient and axial ratio performance of the antenna have been greatly improved.