Electro-textile UHF RFID patch antennas for positioning and localization applications

Passive ultra-high frequency (UHF) radio frequency identification (RFID) provides an attractive technology for indoor positioning and localization. It offers contactless communication, non line-of-sight readability, compactness, and low cost. Localization techniques and algorithms have been actively researched recently from accuracy point of view. However, less attention has been paid to the antenna and its effects on the achieved localization accuracy. Particularly, wearable antennas in human localization applications are key components affecting the achieved accuracy and reliability. In this paper, we elaborate on the material choice for wearable UHF RFID patch antennas. Two highly attractive and flexible conductive electro-textiles are discussed and compared: anisotropic embroidered textile structure and uniform commercially available copper fabric. A patch tag antenna is designed for each electro-textile to operate at 866 MHz. The on-body readability and Received Signal Strength (RSS) in office environment for the antennas are recorded and analyzed. Based on the results we decide on the antenna feasibility in localization applications.