Design And Study Of RFID Reader Antenna And Its Miniaturization

RFID (Radio Frequency Identification) technology, which uses electromagnetic waves forcommunication and data exchange for the purpose of identification, is a non-contact automaticidentification technology. The RFID technology in UHF frequency band(840-960MHz) is a hotspot inthe world, the RFID product at2.45Ghz and5.8GHz are also studied gradually. It is very importantto study and design the reader antenna, which is the key component of the whole RFID system.Firstly, the RFID reader antenna’s related knowledge and the importance of antenna design hasbeen introduced, and a compact RFID reader antenna with impedance bandwidth of835-851MHz,which contain China own frequency of840-845MHz, and peak gain of1.68dBi has been proposedbase of situation that the tag placement is pre-determined.Secondly, this thesis discusses the single patch in the UHF frequency band and analyzes thepattern of polarization and substrate material. Then a single feed circularly polarized RFID readerantenna with DGS(Defected Ground Structure) is proposed. A centre circular slot is adopted forantenna compactness and four rectangular slots are etched on the ground to improve the antenna’sperformance. The simulation result shows that this antenna has a-10dB impedance bandwidth of52MHz(906-958MHz),3dB (Axial Ratio)AR bandwidth of12MHz(917-929MHz), the peak value ofgain is0.8dBi at925MHz, which increase3dBi compared with that of no DGS. In order to furtherimprove the gain, thicker dielectric substrate of5mm is used to improve the gain to3.2dBi. Thesimulation result shows that this antenna behaves good characteristics in the design band, theimpedance and Axial Ratio bandwidth is94MHz and21.3MHz respectively. The antenna structure issimple, easy to fabricate and integration.Finally, the method to realize multiple band work of patch antenna is studied, and to meet thedual-band of reader antenna, slotted patch structure is used to make this design work in920-925MHzand2.4-2.45GHz dual-band and realize circular polarization. The simulation results show that tworesonance frequencies are922MHz and2.451GHz with impedance bandwidth of905-954GHz and2.424-2.470GHz. Axial Ratio below3dB bandwidth of11.6MHz for low-band and31MHz forhigh-band are obtained. The average antenna gain at low-band and high-band is1.6dBi and3.5dBirespectively.