Circularly polarized tag antenna on an AMC substrate for wearable UHF RFID applications

This paper presents a circularly polarized tag on an AMC to achieve longer read range for UHF RFID on-body applications. In the conference paper, two asymmetrically orthogonal cross-dipoles printed on FR4 substrate are combined to generate a degenerate mode for circularly polarization. A symmetric T-matching transformer is employed to conjugate matching with a Monza 4 microchip. The body effect is very significant as the tag is designed for on-body applications. An artificial magnetic conductor (AMC) is placed on the back plane of the cross-dipole tag in order to insulate the influence from a human body. The tag with the AMC can increase antenna gain and achieve over 15 m read range as it is pasted on the human body.