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Localization, wireless monitoring, and emerging body-centric wireless systems demand low-cost and low-power devices that are efficient, maintenance-free, and comfortable to wear. Patch-type UHF radio frequency identification (RFID) tag antennas realized using electro-textiles are promising candidates for this purpose. In this letter, we design a patch-type tag antenna operating at 900 MHz and investigate how different types of ground planes using electro-textiles affect the antenna performance. Various conductive fabrics and embroidery structures are considered. We demonstrate that depending on the ground plane structure and density, it is possible to influence the tag impedance behavior and radiation characteristics. Furthermore, wireless reflectometry measurements are conducted to characterize the sheet resistance for the investigated electro-textiles. We then use the sheet resistance in modeling the conductive fabric ground planes in a full-wave electromagnetic solver. Our results contribute to deeper understanding of the complex electro-textiles structures and guidelines for future practical wearable antenna designs.

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This paper presents the design of a sewed chipless RFID tag and sensor, on a fabric for wearable applications. The proposed design is based on three sewn scatterers on cotton textile. The tag is realized using a computer-aided sewing machine and electro-thread plated with silver. The simulation and frequency-domain measurement results validate the design from 3 to 6 GHz. The tag's static backscattered response can be identified in free space and on the human body. Some preliminary results from a sewn stretchable sensor are also given to demonstrate the potential for biomedical applications. Finally, we discuss the main challenges concerning the practical implementation of this technology.

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