Research On Key Techniques In RFID Integrated Antennas

Radio Frequency Identification (RFID) technology non-contact transfers information and recognizes objects with RF signal. It has the advantages of non-contact, no human intervention, large data storage capacity, strong environment adaptability and high safety etc. It is widely used in the field of logistics tracking, product anti-counterfeiting and asset management. The integrated antenna has the advantages of small size, light weight and easy mass production, so it is widely used in radio frequency identification system. Integrate antennas of RFID system include on-chip antennas, tag antennas and reader antennas. The antenna works as transmitter and receiver. It is of importance in RFID system.This paper begins the study of on-chip antenna, then designs a tag antenna for metal objects. In order to improve the reading range of tag, this paper designs a reader antenna. This paper studies integrity of various parts of RFID antenna. It is organized as follows: Firstly, this paper proposes a novel impedance measurement for balanced tag antennas. This method based on de-embedded see the fixture as a two port network. The impedance of antenna can be accurately measured without establishing the fixture model.Secondly, this paper studies the tag on-chip antenna for the purpose of realizing the miniature of tag. Based on silicon integrated inductance model, this paper analyses the parasitic losses. It simulates the substrate structure of the chip, the results show the antenna impedance variable with the changing of parameters of substrate structure.Thirdly, this paper designs RFID tag antenna for metal objects based on embedded fed microstrip antenna. The antenna can be flexible and large range of antenna impedance adjustment. The resistance and reactance of antenna are changed by adjusting the embedded depth of radiating patch and length of feedline. The effect of metal plate size and the distance between the tag antenna and the metal plate on the performance of the metal tag antenna is analyzed. The reading distance of theoretical calculation of design antenna on the metal plate is 4.8 meters.Finally, this paper designs an UHF RFID reader dual ports antenna. Different with the single port antenna, the dual ports antenna separates transmitting and receiving signal. Thus it reduces the interference of tag backscattering signal from transmitting signal and improves the ability of reader of receiving tag signal. According to requirement of reader dual ports antenna, this paper designs an aperture coupled microstrip antenna operating 2.4 GHz band. The antenna utilizes T shaped feedline to excite apertures. With the purpose of degrading ports isolation, two T shaped feedlines are placed vertically to form orthogonal polarization. In order to couple the energy from feedline to patch and produce linear polarization, two U shaped apertures are etched on the ground plane. The measurement results of fabricate antenna show the ports isolation is less than -25 dB in 2.4 GHz band and the antenna can be utilized as UHF RFID reader antenna.