UHF RFID Tag Antennas Research And Design

At present,radio frequency identification technology is one of the wireless communication technology which uses the radio frequency signal to activate the tag to read and obtain the unique encoded information of the tag chip on the target object.RFID is widely used in vehicle management system and safe system.The gain of tag antennas directly influences the reading distance.This paper designs two tag antennas for electronic registration identification,the anti-metal tag antennas and a near and far field of tag antenna.Firstly,two tag antennas for ERI(Electronic Registration Identification)of the motor vehicle are designed.The first tag antenna for ERI uses double closed loop.The bandwidth of first antenna is 840-993MHz over the entire UHF RFID band and the gain of first antenna is 2.5dBi.Theoretically,the reading distance of first tag antenna surpassed the required.But the operating frequency of first tag antenna is 925MHz which deviate the required center frequency.Second tag antenna for ERI using snap ring achieved good impedance matching in 915MHz.The bandwidth of second antenna is 820-988MHz over the entire UHF RFID band and the gain of second antenna is 2.5dBi.Theoretically,the reading distance of second tag antenna surpassed the required reading distance of ERI.Meanwhile,we processed and tested the second tag antenna and analyzed the test results.The novelty is slotting the closed loop dipole antenna,which realizes the optimization of impedance matching for tag antennas and strengthens the matching depth of tag antennas.Secondly,we do some research into the tag antennas on the metal surface and designed the anti-metal tag antenna and the anti-metal CP(Circularly Polarized)tag antenna.The anti-metal tag antenna combines bow-tie dipole antenna and rectangular snap ring.The operating frequency of the anti-metal tag antenna is 842.5MHz.The bandwidth of the anti-metal tag antenna is 611-1013MHz over the entire UHF RFID band and the gain of the anti-metal tag antenna is 3.1dBi at 842.5MHz.This anti-metal tag antenna achieves good performance characteristic with the size of 100×100 100mm2,200×200mm2 and 300x300mm2 of metal plate,respectively.The anti-metal CP tag antenna symmetrical feed for loop antenna.The operating frequency of the anti-metal CP tag antenna is 842.5 MHz.The bandwidth of the anti-metal CP tag antenna is 533-1066MHz over the entire UHF RFID band and the gain of the anti-metal CP tag antenna is OdBi at 842.5MHz.This anti-metal CP tag antenna achieves excellent performance characteristics on 100×100mm2,200×200mm2 and 300x300mm2 of metal plate,respectively.The anti-metal tag antenna and the anti-metal CP tag antenna can satisfy the requirements.The novelty is grounding via hole which realizes anti-metal and proposing symmetrical feed for loop antenna which realizes CP.Finally,a near and far field of tag antenna is designed.This antenna achieves excellent performance characteristic by combining loop-antenna and dipole antenna.The operating frequency of the near and far field tag antenna is 915MHz.The near and far field tag antenna which bandwidth over 580MHz-1080MHz and accomplish uniform magnetic near-field distribution.And the gain of antennas is 1.7dBi.The novelty is slotting the closed loop dipole antenna,which realizes the optimization of impedance matching for tag antennas and strengthens the matching depth of tag antennas.The novelty is proposing the double ring,which realizes the optimization of impedance matching for tag antennas and accomplish good match.