ID-Yarn: Form-factoring an RFID Tag into a Yarn and How It Can Work Well

We propose a novel design for RFID tags - ID-Yarn, in which an RFID tag is integrated into a yarn suitable for weaving, embroidery, or seam attachment to fabric. ID-Yarn comprises an RFID transponder chip soldered with a conductive filament onto the chip pads. The chip and the filament are then enveloped with non-conductive fibers, creating a yarn structure. The conductive filament within the ID-Yarn serves as a dipole antenna, and various dipole antenna configurations can be achieved by shaping the ID-Yarn into different geometries. We have introduced three dipole variations: a dipole with varied arms for conjugate-matching the chip impedance, a dipole with meander-lined arms, and a dipole with looped arms. Simulations and prototypes of these variations demonstrate the feasibility of ID-Yarns. Notably, the ID-Yarn shaped into a looped dipole geometry exhibits the best performance.