Effect of Stitch Structure on the Reading Performance of Fabric-Based Embroidered UHF RFID Tags

Abstract

As the demand for low-cost rapid preparation techniques for RFID (Radio Frequency Identification) fabric tags is increasing, embroidery technologists have attempted to fabricate tag antennas. However, the effects of stitch structures on the performance of tag antennas have rarely been studied. Since the structure of an embroidered stitch is related to the embroidering process parameters and embroidery thread, this study chose a common stitch trace type to prepare two sets of UHF RFID tag antennae by changing the embroidery thread structure and stitch length, and then the electrical and gain properties of these antennas were analyzed. And again, the reading performance of the corresponding tag was evaluated. The results showed that the antennas embroidered with copper/PET wrapped yarns have higher energy transfer efficiency than those with single copper wire yarns. When the stitch length increases from 0.9 to 5 mm, the read range of the embroidered tag firstly increases and then decreases, due to the large embroidering process deviation of the tag antenna geometry, and the optimal stitch length for the read range is 1.7 mm, where the read range is 12.95 m. When the stitch length is 5 mm, the read range is minimum – 9.56 m. In summary, this study determined the embroidered thread structure and the process design of the stitch length in terms of the performance of a fabric-based embroidery antenna for an RFID tag as well as the read range.