Folded Antipodal Dipole for Metal-Mountable UHF Tag Design

Abstract

A compact folded dipole antenna that consists of two C-shaped arms, which are placed in the antipodal constellation, is proposed for designing a metal-mountable miniature tag antenna in the UHF band. Here, each of the dipole arms is composed of four unequal line segments for reducing the current crowding effect and for improving the tag’s performance. Two inductive shorting stubs are introduced for tuning the tag’s resonant frequency. The proposed tag antenna is made using a flexible substrate and it is electrically small, having a circuit size of 50 mm $\times30$ mm $\times1.6$ mm ( $0.153\lambda \times 0.092\lambda \times 0.005\lambda$ ). It has been found that conjugate match can be easily obtained by adjusting the dimensions of the C-shaped arms and the inductive shorting stubs. When mounted on metal, the proposed tag antenna is able to achieve a maximum read distance of 9.1 m at the equivalent isotropic radiated power of 4 W. The proposed tag antenna is found to be platform insensitive and it can read beyond 7 m when placed on dielectric objects.