Analysis of the power transfer and electrical performances of an embroidered textile loop antenna for near field communication (NFC) application

We present a new class of wearable textile antenna and analyse their performances through an electrical study. The developed prototypes have been realized by an embroidery process and are made of conductive twisted copper/polyester yarns on a cotton substrate. These antennas aim to transfer power and data thanks to the NFC technology, so the operating frequency is 13.56MHz and the maximal reading distance is around 10cm. The strong resistance of the yarn (4.20/m) make us overlap three yarns to reach satisfactory electrical characteristics. Antennas are composed of a textile plan circular coil to which we add a usual capacitor. The study of coils electrical characteristics highlights a linear evolution of coil resistance and inductance in function of embroidery geometrical parameters. Also, these data show the feasibility of such antennas, especially through quality factor values reaching 45.