Linearly tapered meander line cross dipole circularly polarized antenna for UHF RFID tag applications

Abstract

In this article, a circularly polarized antenna for ultra-high frequency radio frequency identification (RFID) tag is presented. The circular polarization is realized by two orthogonal, unequal length linearly tapered meander line cross dipoles. The meander structure with capacitive tip loading is used for size miniaturization of the antenna. A modified T-match network is employed to feed the cross dipole structure. The measured 10-dB return loss bandwidth of the cross dipole antenna is 17 MHz (908-923 MHz) and the corresponding 3-dB axial ratio bandwidth is 6 MHz (912-918 MHz). The overall size of the proposed antenna is 0.17λ0 × 0.17λ0 at 915 MHz. The maximum read range between the reader and the tag with the proposed antenna is 4.7 m larger than the analogous linearly polarized tag antenna due to the reduction in polarization loss between the tag and reader antennas. Thus, a maximum read range of 15.66 m with the gain of 1.28 dBic is achieved at 915 MHz.