Design Of Multifunctional RFID Reader Antenna

Radio Frequency Identification(RFID)is a kind of non-contact automatic Identification technology,which is widely used in warehouse goods management,manufacturing,vehicle automatic charging system,medicine,finance and other fields.Especially in the ship intelligent logistics management system,RFID subsystem has become an essential part.Antenna is an indispensable unit of RFID reader.Its functions such as miniaturization,high isolation degree,dual band and dual polarized have important practical application value.This thesis researches and designs miniaturized,high isolation,dual-band and dual-polarized RFID reader antennas,and obtains the following results:(1)A dual-polarized microstrip antenna with high isolation is designed.The antenna works in the 2.45 GHz RFID band and is fed by two ports.One port is horizontally polarized and is fed by microstrip line side,and the other port is vertically polarized and is fed by gap coupling.Through the improvement of the traditional rectangular feed strip and the optimization of the floor gap,the impedance bandwidth of the two ports is 2.38-2.49 GHz and2.39-2.49 GHz respectively,and the test isolation of the ports is greater than 57 d B in the2.4-2.483 GHz working band.The results show that the antenna can be used for the transceiver isolation of readers or the common antenna of two readers.(2)A dual-band circularly polarized antenna fed by a single port is designed.The circular radiation patch is loaded with an asymmetric windmill groove to realize the dual-band circularly polarized radiation.In the 920MHz/2.45 GHz working band,the impedance matching is good,the polarization mode of the two bands is right-hand circular polarized,and the axial ratio is less than 3d B in the band range,the test gain is greater than-1.8d Bic/3.5d Bic respectively.The results show that the antenna can radiate circularly polarized waves in both 920MHz/2.45 GHz bands,which can meet the requirements of engineering applications.(3)One T-type power divided phase-shifting feed network feeds energy of equal amplitude and phase lag by 90 degrees to four inverted-F antennas,which realizes a small right-handed circular-polarized 0.865 GHz antenna.A 5.8GHz circularly polarized patch antenna was designed using the available space between the four curved inverted F antennas,resulting in a dual band dual circularly polarized reader antenna in the 0.865/5.8GHz band.The impedance bandwidth and 3-d B axial ratio bandwidth of the antenna can fully cover the RFID(0.865-0.868GHz)and WLAN(5.725-5.85GHz)bands,and the gain of the tested antenna is greater than 1.82 d Bic/6.02 d Bic,respectively.Compared with the traditional microstrip patch antenna,the size of the antenna is reduced by 65.3%.Compared with the similar antennas provided in the existing literature,it is shown that the integrated performance of the designed antenna is better.