Flexible Textile-Based Coaxial Transmission Lines for Wearable Applications

Flexible and lightweight textile-based coaxial transmission lines for wearable applications are presented. In particular, textile yarns defined by copper (Cu), polyester (PES), and polytetrafluoroehtylene (PTFE) materials were used to design transmission line prototypes offering a 50- Ω characteristic impedance. These structures, which have the weight and texture of a cylindrical shoe lace, were also simulated and measured using a commercial simulator and results are in agreement. In addition, the textile cables were also studied in various straight, bent and wet conditions to ensure flexibility and durability whilst observing low reflection and insertion losses in these scenarios. In addition, the mass and DC losses of the fabricated cables were measured and are competitive when compared to a commercially available cable. To the best knowledge of the authors, this is the first implementation of simple RF/microwave coaxial cables whilst achieving a 50- Ω characteristic impedance, made possible by using purely wearable yarns and materials, whilst adopting a textile braiding process during manufacturing. Findings suggest that the reported textile-based cables are suitable for data connectivity between wearable devices in the UHF and the 2.4 GHz ISM frequency bands, for example, and can provide an alternative to more established strategies for wireless connectivity between body worn IoT devices and other related technologies.