Miniature Dipolar Patch UHF RFID Tag Antenna for Metal and Dielectric Surfaces

Abstract

A rectangular dipolar patch is proposed for designing a UHF RFID tag antenna that is suitable for metal and dielectric surfaces. The proposed tag antenna has a very compact structure with a dimension of 46 mm × 15 mm × 1.7 mm. It consists of a circular matching loop surrounded by two highly capacitive loading radiating patches, creating an embedded structure that has a very small size. Two L-shaped slot lines are etched in the radiating patches for lengthening the electrical length of the radiating patches. The low-profile dipolar patch is capacitive in nature, and the inclusion of a circular matching loop is an effective way to make the tag antenna inductive to achieve good impedance matching with the microchip. Series of simulations have been performed to evaluate the characteristics of the proposed tag antenna. When measurement is done on dielectrics based on North America regulated Radiated Power (EIRP) of 4 W, the tag antenna is managed to radiate beyond 8.5 m, but it decreases to 2.5 m when being placed on metallic surfaces. A noteworthy fact is that the resonant frequency of the proposed tag antenna is preserved and is not greatly affected by the type of materials attached to it. To our best knowledge, the proposed tag is performing much better than other recently published tags for the same application, with a relatively simpler antenna structure.