Circularly polarized unidirectional antenna using planar tennis shape structure

This paper presents the study and the design of the circularly polarized reader antenna with a tennis ball-shaped radiating plate operating at the universal UHF band (860-960 MHz). The proposed antenna is excited by a capacitively coupled feed technique to enhance |S₁₁|. The tennis ball-shaped radiating plate can be generated a circularly polarized radiation. The simulation is studied effect of the parameters of the proposed antenna for cover the universal UHF RFID band. The prototype antenna is achieved, |S₁₁| cover the frequency between 837.60 to 966.20 MHz, the 3-dB axial ratio (AR) bandwidth cover the frequency from 850.60 to 963.50 MHz, a unidirectional radiation pattern and an average gain 6.18 dBic, respectively.