UHF RFID elastic textile yarn

Over the last decade, the wearable electronics has greatly improved and the wearables market is expected to increase exponentially in the next years. Ultra high frequencies (UHF) radio frequency identification (RFID) textile yarns represent one of the most relevant solutions for adding smart functionality into clothes and more generally for any object integrating a textile tag. Among the existing textile yarn solutions, the E-Thread technology consists on electronics embedded into textile yarn using a micro-encapsulation method. This technology is the starting point of the work presented in this article. One of the hardest constraints that the RFID yarn should overcome is the robustness against stretching. Thus, the antenna has to be tolerant to the deformation of the associated textile yarn. Unlike the half-wave dipole antenna used in the current E-Thread yarn, the proposed solution is based on helical dipole antenna topology because its geometry naturally makes feasible an axial stretching. This study details the manufacturing process as well as the design methodology of the antenna taking into account the RFID context as well as the constraints imposed by the manufacturing process. The impact of the antenna's physical parameters is highlighted in order to provide design guidelines. The helical dipole antenna enables until 16% of axial elongation while the dipole antenna would tear apart.