Research Of UHF RFID Near-field Reader Antennas

With the propose of item-level identification,ultra-high frequency(UHF)near-field radio frequency identification(RFID)system has been received extensive attention and applications for its high data transmission rate and stable near-field performance.In this thesis,three UHF RFID near-field reader antennas in large size are fabricated.The main research work is as follows:1.An enlarged interrogation zone has been achieved by four square-segmented loops,with double-sided parallel-strip line(DSPSL)feeding network.The zero and reverse phase of the current on the loop is solved by a segmented coupling structure.The measured impedance bandwidth of the antenna is 128MHz.With the input power of 20d Bm,the antenna reaches 100%read percentage within the height of 20mm,and the interrogation zone is 690×225mm~2.2.A UHF near-field reader antenna with a large reading distance is designed.The antenna is mainly composed of two meander open-ended microstrip lines and periodically slits to generate a strong uniform electric-field distribution without null zones.The measured impedance bandwidth of the antenna is 104MHz.With the input power of 30d Bm,the height of the 100%read percentage reaches at 350 mm.Meander line elements with simple structure are introduced,and it can be adapted to the specific scenarios by increasing or decreasing the number of elements.3.A near-field RFID reader antenna based on six microstrip antenna elements coupling is proposed.By adjusting the electrical length between the elements,a strong and uniform electric field is generated,and a better reading performance of the tool cabinet management system can also be achieved.The simulation results show that the metal environment has little effect on the antenna performance.After fabricated and measured,the antenna has good impedance performance in the900-955MHz.With the input power of 27d Bm,the interrogation zone is 680×145 mm~2,and within the height of 450mm the antenna can obtain100%read percentage.