DESIGN OF A RFID READER ANTENNA FOR PERSONAL DIGITAL ASSISTANT (PDA)

Abstract

In this thesis, a circularly polarized microstrip antenna with vertical ground for UHF RFID reader antenna is proposed. To understand its background, brief history and basic structure of the RFID system are reviewed. The designed reader antenna operates in UHF band less than 1 GHz. For this reason, the size of an antenna volume would be big relatively to other mobile antenna, unless without high relative permittivity substrate. To overcome this limitation, antenna size reduction techniques are needed to achieve proper mobile antenna size. In this thesis, a vertical ground is used to reduce the overall size of an antenna while satisfying the bandwidth requirement. The proposed antenna is composed of a radiating patch and a vertical ground surrounding four sides of the substrate. The use of vertical ground reduces the resonant frequency about 25 % comparing to that without vertical ground. The height of the air layer between the ground plane and the substrate determines radiation efficiency and impedance characteristic. Result shows that the designed antenna has good impedance and radiation characteristics over the frequency band of interest. The dimension (100×100×13 mm3) of the proposed antenna is suitable to be used for a handheld PDA terminal.