A Dual-ID RFID Tag for Headgear Based on Quasi-Yagi and Dipole Antennas

In this article, we present a dual-ID radio frequency identification (RFID) headgear based on quasi-Yagi antenna where we reuse the reflector element as the second dipole antenna that provides radiation pattern upward from the user's head. Thus, we achieve simultaneously the broadside and endfire patterns without increasing the size of the antenna platform. For avoiding the unpredictable impact of the surface of the human body to the electromagnetic properties of the antenna platform, we inserted a periodic surface made up of a 2-by-2 grid of square loops beneath it. It facilitates launching of surface waves thereby enhancing the endfire radiation for the quasi-Yagi antenna and its back metal plate isolates the antenna platform from the human body. We have fitted the whole structure on the headgear by folding the quasi-Yagi antenna elements and created the antenna on a low-permittivity textile substrate. Moreover, we have modeled the antenna in both simple and anatomical head models, both including curvature, and measured the attainable read ranges of 6.8 m and 5 m, for the quasi-Yagi and dipole tags, respectively, in head-worn configuration.