Reliable UHF Long-Range Textile-Integrated RFID Tag Based on a Compact Flexible Antenna Filament

Abstract

This paper details the design, fabrication and testing of flexible textile-concealed Radio Frequency Identification (RFID) tags for wearable applications in a smart city/smart building environment. The proposed tag designs aim to reduce the overall footprint, enabling textile integration whilst maintaining the read range. The proposed RFID filament is less than 3.5 mm in width and 100 mm in length. The tag is based on an electrically small (0.0033 λ 2 ) high-impedance planar dipole antenna with a tuning loop, maintaining a reflection coefficient less than −21 dB at 915 MHz, when matched to a commercial RFID chip mounted alongside the antenna. The antenna strip and the RFID chip are then encapsulated and integrated in a standard woven textile for wearable applications. The flexible antenna filament demonstrates a 1.8 dBi gain which shows a close agreement with the analytically calculated and numerically simulated gains. The range of the fabricated tags has been measured and a maximum read range of 8.2 m was recorded at 868 MHz Moreover, the tag’s maximum calculated range at 915 MHz is 18 m, which is much longer than the commercially available laundry tags of larger length and width, such as Invengo RFID tags. The reliability of the proposed RFID tags has been investigated using a series of tests replicating textile-based use case scenarios which demonstrates its suitability for practical deployment. Washing tests have shown that the textile-integrated encapsulated tags can be read after over 32 washing cycles, and that multiple tags can be read simultaneously while being washed.

Omnidirectional Dual-Polarized Low-Profile Textile Rectenna With Over 50% Efficiency for Sub-μW/cm2 Wearable Power Harvesting

“…Features down to 150 µm, such as surface mount components pads, can be easily resolved using a commercial copper etcher and a standard UV light source without the need for a clean room environment. Textile-based electronics require encapsulation for improved reliability [31], [32]. Fabricating flexible circuits on thin polyimide filaments for textiles integration support encapsulation techniques such as vacuum-forming [32].…”

“…Textile-based electronics require encapsulation for improved reliability [31], [32]. Fabricating flexible circuits on thin polyimide filaments for textiles integration support encapsulation techniques such as vacuum-forming [32]. Encapsulated RFID tags have been demonstrated withstanding over 30 machine washing cycles [32].…”

A Review of Flexible Wearable Antenna Sensors: Design, Fabrication Methods, and Applications

“…In fact, this is one of the important considerations for wearable electronics design [ 58 ]. Several flexible wearable antenna sensors are implemented on different types of materials such as papers [ 59 ], fabrics [ 60 ], and plastics [ 61 ]. Plastic substrates are neither recyclable nor biodegradable, as they affect environmental pollution and involve many health problems.…”

Wearable Textile UHF-RFID Sensors: A Systematic Review

“…Certainly, the common materials, PCB, can be applied for multi-sensor structures in terms of multi layers, as shown in Figure 4a, which also gives textile UHF-RFID sensors a novel research orientation towards multi-layer structures with flexible and comfortable features. [45]); (b) UHF-RFID tag with polyimide substrate (adapted from [40]); (c) UHF-RFID tag with 50% cotton and 50% polyester substrate (adapted from [44]).…”