Characterization of embroidered dipole-type RFID tag antennas

Radio Frequency Identification (RFID) is a technology which is used for automatic identification of objects. A typical RFID system consists of a stationary radio-scanner unit, called reader, and a movable transponder, called tag, which is attached to an object. The tags include an antenna and a microchip with internal read/write memory. Tag antenna plays an important role in the overall RFID system performance factors, such as the read range, and the compatibility with tagged objects. This thesis focuses on garment-integrated embroidered tags which can be used for the means of human monitoring and identification. The embroidered tag antennas are sewed on fabric using conductive threads and computer aided sewing machine. Modeling of embroidered tag antennas is not a straightforward task, because embroidered antennas do not have a distinct conductivity, which could be used in the simulation model of them. In fact, conductivity of sewed flat conductive layer depends on the selection of the conductive thread, the thread and stitch density and the sewing pattern. The aim of this thesis has been to investigate the effect of these factors on the conductivity, and evaluate conductivity values for the embroidered dipole-type RFID tag antennas. In this project, T-matched dipoles have been sewed on cotton with two different sewing patterns and also with many different stitch densities. The effect of the geometry of the antenna is also investigated by sewing and measuring straight simple dipoles with both sewing patterns. The achieved read range values of the sewed tag antennas have been up to 7.5 m. In this thesis it is proved that each sewing pattern has its own conductivity and con-ductivity of a sewing pattern improves if the pattern consists of sewed lines along the direction of current flow. It is not necessary to sew the antenna with a high thread and stitch density. We can achieve high conductivities even from very sparsely sewed an-tennas, using less conductive threads and spending considerably less time on sewing. The evaluated conductivities and the presented simulation model of the sewed dipoles in this project can be used in future for optimization of the sewed antennas to operate in the vicinity of body

Textile UHF-RFID antenna sensors based on material features, interfaces and application scenarios

Tesi en modalitat de compendi de publicacions, amb una secció retallada per drets de l'editor. In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of Universitat Politècnica de Catalunya's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to http://www.ieee.org/publications_standards/publications/rights/rights_link.html to learn how to obtain a License from RightsLink.Radio frequency identification over measurable ultra-high frequency textile substrates (UHF-RFID) is a promising technology to develop new applications in the field of health and the Internet of Things (IOT), due to the massive use of fabrics and the technological maturity of embroidery techniques. This thesis is the result of a compendium of publications on this topic. First, as a result of the analysis of the state of art, a systematic review entitled 'Wearable textile UHF-RFID sensors: A systematic review' has been published. The thesis aims to improve research on UHF-RFID textile-based sensor technology. Thanks to the analysis of the state of art, three novel research objectives have been set that are worth exploring. The first is to study novel detection functions for textile UHF-RFID based sensor technology; the second is to find a connection/interface solution between textile antennas and integrated circuit (IC) chips and the third is to reduce the costs of such technology to promote future commercial applications. To contextualize the thesis, it includes the necessary theoretical fundamentals and the manufacturing and characterization methods used during it. As a result of the work derived from the first objective, a scientific article entitled “Textile UHF-RFID Antenna Sensor for Measurements of Sucrose Solutions in Different Levels of Concentration” has been published. In this work, a textile UHF-RFID tag with two detection positions is proposed for sucrose solution measurements. The two detection positions with the different detection functions show good performance and can offer two options for future full applications. In addition, another scientific article entitled “ Textile UHF-RFID Antenna Embroidered on Surgical Masks for Future Textile Sensing Applications” has been published to support the first objective. The inspiration for this work came from the current pandemic situation. This work develops three progressive designs of textile UHF-RFID antennas over surgical masks due to the current global epidemic situation. Reliability testing demonstrated that the proposed designs can be used for human healthcare focused applications. As a result of the second objective, a research article entitled 'Experimental Comparison of Three Electro-textile Interfaces for Textile UHF-RFID Tags on Clothes' has been published. This work proposes three electro-textile interfaces integrated with the corresponding textile UHF-RFID antennas and provides the chip-textile connection solutions (through sewing, push buttons and insertion). As a result of this objective, an electro-textile interconnect system has been proposed together with its electrical model, which allows the correct adaptation of impedances between the RFID antennas and the integrated circuit. It is worth noting that the mixed-use feasibility of the proposed electro-textile interfaces and the designed textile UHF-RFID antennas has been verified, reducing the cost in the design procedure in applications where the read range requirements of the order of 1 meter. The third objective has been achieved and exposed by a scientific article entitled 'Electro-textile UHF-RFID Compression Sensor for Health-caring Applications'. It proposes a single UHF-RFID based compression textile sensor that can be used simultaneously in two different healthcare application scenarios, which directly impacts on cost reduction.La identificación por radiofrecuencia sobre substratos textiles de ultra alta frecuencia (UHF-RFID) con capacidad de medida es una tecnología prometedora para desarrollar nuevas aplicaciones en el campo de la salud y el Internet de las cosas (IOT), debido a la masiva utilización de los tejidos y a la madurez tecnológica de las técnicas de bordado. Esta tesis es el resultado de un compendio de publicaciones sobre dicha temática. En primer lugar, como resultado del análisis del estado del arte se ha publicado una revisión sistemática titulada 'Wearable textile UHF-RFID sensors: A systematic review'. La tesis tiene como objetivo mejorar la investigación sobre la tecnología de sensores basada en textiles UHF-RFID. Gracias al análisis del estado del arte se han fijado tres objetivos de investigación novedosos que vale la pena explorar. El primero es estudiar funciones de detección novedosas para la tecnología de sensores basada en UHF-RFID textiles; el segundo es encontrar una solución de conexión/interfaz entre antenas textiles y chips de circuito integrado (IC) y el tercero es la reducción de costes de dicha tecnología para promover futuras aplicaciones comerciales. Para contextualizar la tesis, ésta incluye los fundamentos teóricos necesarios y los métodos de fabricación y caracterización utilizados durante la misma. Como resultado del trabajo derivado del primer objetivo, se ha publicado un artículo científico titulado “Textile UHF-RFID Antenna Sensor for Measurements of Sucrose Solutions in Different Levels of Concentration”. En este trabajo, se propone una etiqueta UHF-RFID textil con dos posiciones de detección para mediciones de solución de sacarosa. Las dos posiciones de detección con las diferentes funciones de detección muestran un buen rendimiento y pueden ofrecer dos opciones para futuras aplicaciones completas. Además, se ha publicado otro artículo científico titulado "Textile UHF-RFID Antenna Embroidered on Surgical Masks for Future Textile Sensing Applications" para respaldar el primer objetivo. La inspiración para este trabajo vino de la actual situación de pandemia. En este trabajo se desarrollan tres diseños progresivos de antenas UHF-RFID textiles sobre mascarillas quirúrgicas debido a la situación epidémica mundial actual. Las pruebas de fiabilidad demostraron que los diseños propuestos se pueden usar para aplicaciones centradas en el cuidado de las personas. Como resultado del segundo objetivo, se ha publicado un artículo de investigación titulado 'Experimental Comparison of Three Electro-textile Interfaces for Textile UHF-RFID Tags on Clothes'. En este trabajo se proponen tres interfaces electro-textiles integradas con las correspondientes antenas UHF-RFID textiles y se aportan las soluciones de conexión chip-textil (mediante costura, botones a presión e inserción). Como resultado de este objetivo, se ha propuesto un sistema de interconexión electro-textil junto con su modelo eléctrico, lo que permite la correcta adaptación de impedancias entre las antenas RFID y el circuito integrado. Vale la pena señalar que se ha verificado la viabilidad de uso mixto de las interfaces electro-textiles propuestas y las antenas UHF-RFID textiles diseñadas, lo que reduce el coste en el procedimiento de diseño en aplicaciones donde los requerimientos de rango de lectura del orden de 1 metro. El tercer objetivo se ha alcanzado y expuesto mediante un artículo científico titulado 'Electro-textile UHF-RFID Compression Sensor for Health-caring Applications'. En él, se propone un único sensor textil de compresión basado en UHF-RFID que puede ser utilizado a la vez en dosPostprint (published version

Textile UHF-RFID antenna embroidered on surgical masks for future textile sensing applications

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Ultra High Frequency (UHF, 865-868 MHz) Radio Frequency Identification (RFID) devices are expected to be implemented in many health-caring areas. In this paper, we present three progressive designs of textile UHF-RFID antennas on surgical masks using a function-extensible integrated circuit (IC) chip (Rocky 100). The simulated and measured resonance curves of the designs all match well (|S11| < -20 dB at 868 MHz) and the maximum realized gain are improved progressively in order to overcome the difficulty of the chip low sensitivity and increase the maximum read range. The best type (Design 3) is selected and its read range measured by the RFID reader (M6e kit) can reach 2.5 m in air. In addition, several reliability validation measurements are performed, such as bending and skin contact, and maximum read range can reach 1.1 m considering the on-body worn worst case. The proposed Design 3 allows common use as a tag for tracking or safe distance alert under an epidemic situation. Alternatively, for the used function-extensible chip, the design can be applied to many different types of sensors for various application scenarios.This work was supported in part by Spanish Government-MINECO under Project TEC2016-79465-R, and China Scholarship Council under Grant No.201908440233.Peer ReviewedPostprint (author's final draft

Embroidery Leaf Shape Dipole Antenna Performances and Characterisation

In this paper, leaf shape textile antenna in ISM band has been chosen to study. The operating frequency of the dipole antenna is 2.45GHz. The effect of conductive threads with three different types of sewing has been analysed. The first type of sewing leaf shape dipole antenna is to stitch around itself and embroidered into a fleece fabric with circular follow by vertical and horizontal stitch respectively. From measured return loss, the antenna with circular stitch shows better performances with optimum resonances compared with the two types of stitching. The measured results confirm that the circular stitch is more suitable for leaf shape dipole antenna design. Thus it can be concluded that different stitch gives different results for leaf shape dipole antenna

Characterization and Design Methodologies for Wearable Passive UHF RFID Tag Antennas for Wireless Body-Centric Systems

Radio Frequency Identification (RFID) is a wireless automatic identification technology that utilizes electrically active tags – low-cost and low-power wireless communication devices that let themselves transparently and unobstructively be embedded into everyday objects to remotely track information of the object’s physical location, origin, and ownership. At ultra-high frequencies (UHF), this technology uses propagating electromagnetic waves for communication, which enables the fast identification of tags at large distances. A passive RFID tag includes two main components; a tag antenna and an RFID integrate circuit (tag IC). A passive tag relies solely on the external power harvested from an incident electromagnetic wave to run its circuitry and for data transmission. The passiveness makes the tag maintenance-free, simple, and low-cost, allowing large-scale commercial applications in the supply chain, ticketing, and asset tracking. The future of RFID, however, lies in the transition from traditional embedded applications to wearable intelligent systems, in which the tags are seamlessly integrated with everyday clothing. Augmented with various ambient and biochemical sensors, the tag is capable of detecting physical parameters of its environment and providing continuous monitoring of human vital signs. Tremendous amount of tagged entities establish an intelligent infrastructure that is personalized and tailored to the needs of each individual and ultimately, it recedes into the background of our daily life. Although wearable tags in intelligent systems have the enormous potential to revolutionize the quality of human life, the emerging wearable RFID applications introduce new challenges for designers developing efficient and sophisticated RFID systems. Traditional tag design parameters and solutions will no longer respond to the new requirements. Instead, the whole RF community must adopt new methods and unconventional approaches to achieve advanced wearable tags that are highly transparently integrated into our daily life. In this research work, an empirical as well as a theoretical approach is taken to address the above-mentioned wearable RFID tag challenges. Exploiting new analysis tools in combination with computational electromagnetics, a novel technique to model the human body in UHF applications for initiating the design of optimized wearable tags is developed. Further, fundamental unprecedented UHF characteristics of advanced wearable electronics materials – electro-textiles, are established. As an extremely important outcome of this research work, innovative optimization methodologies for the promotion of novel and advanced wearable UHF antennas are proposed. Particularly, it is evidenced that proper embroidery fabrication techniques have the great potential to realize wearable tag antennas exhibiting excellent RF performance and structural properties for the seamless integration with clothing. The kernel of this research work is the realization of a flexible and fully embroidered passive UHF RFID patch tag prototype achieving optimized performance in close vicinity of the high-permittivity and dissipative human body. Its performance may be considered as a benchmark for future wearable antenna designs. This shows that this research work outcome forms an important contribution to the state of the art and a milestone in the development towards wearable intelligence

Evaluation of conductive threads for optimizing performance of embroidered RFID antennas

Radio frequency identification (RFID) refers to a technology that utilizes radio signals for identifying objects automatically. This technology consists of a reader that detects the objects and a transponder that gets attached to the object and it is called tag. The tag is an enclosure that houses the antenna and an IC that stores the necessary information on that object. This thesis focuses tag antennas made for embroidered RFID. Embroidered antennas are made by sewing antenna using conductive thread onto a fabric using a computerized sewing machine. This enables us to extend the field of RFID technologies to textiles. Conventional RFID systems that use metal conductors are easy to model but the same cannot be said for embroidered RFID. The reason being conductive threads and embroidered antennas don’t have definite conductivity. The conductivity of an embroidered antenna depends multiple factors like thread conductivity, thread density, stitch density, sewing pattern etc. The target of this thesis is experimenting with conductive threads physically and for their conductivity followed by eval-uating them for the use of embroidered RFID antenna fabrication for optimizing the perfor-mance. In this thesis, using same antenna pattern and technique, tags were fabricated from 6 differ-ent conductive threads onto the same cotton fabric. The conductive threads were investigated for their conductivity, thread thickness and their strength. The antennas were tested for their read range and the effect of different threads on the antenna were analysed. The threads with the highest conductive nature gave the highest read range of 6.2 meters. The threads were also evaluated for their usability for embroidery. Some threads were too thick, some had exposed structures leading to malfunction in the sewing machine and others were too thin and ripped easily during sewing. The selected thread should not only have great performance, but also it needs to be practical. It is seen that the conductivity of antenna and hence the performance is easily improved with using high conductive thread. After taking all the factors into account, finally a thread was selected that can be used to make high performance embroidered RFID antennas and also highly suitable for embroidery process. In the future, the same work can be revisited or extended to other more versatile and higher conductivity threads. Also, the advancement is embroidery techniques will allow for more con-ductive threads to be compatible for embroidery opening more options for optimization

Design and Characterization of a Flexible Wideband Antenna Using Polydimethylsiloxane Composite Substrate

The design and characterization of a simple, flexible wideband antenna using polydimethylsiloxane (PDMS) composite are presented. Conductive fibers are used to construct the metallic parts on a PDMS composite. To characterize the performance, two identical antennas are designed, one using the PDMS composite while the other on conventional dielectric materials. It was observed that both antennas behave well in terms of the matched bandwidth; however, the radiation towards the broadside direction is reduced when using the PDMS composite as substrate, particularly at higher frequencies. The antenna exhibits a matched bandwidth of 59.9%, ranging from 3.43 to 11.1 GHz. Moreover, the bending analysis carried out for different scenarios show that the wideband behavior of the antenna is well preserved and the variation reaches a maximum of 1% variation

The Design, Fabrication and Practical Evaluation of Body-centric Passive RFID Platforms

Passive ultra-high-frequency (UHF) radio-frequency identification (RFID) technology is increasingly being recognized as a compelling approach to utilizing energy- and costefficient wireless platforms for a wireless body area network (WBAN). The development of WBANs has stimulated a lot of research over recent years, as they can offer remarkable benefits for the healthcare and welfare sectors, as well as having innovative sportsrelated applications.This thesis is to evaluate and develop the RFID tags used in an integrated wearable RFID platform working in a realistic environment. Each of the wearable antennas were specifically designed for a target part of the body, such as the back or the hand. The antennas were manufactured in different ways, using copper tape, electro-textiles (Etextile) and embroidered conductive threads. After they had been produced, the tags were subjected to on-body measurement and reliability tests. The reliability tests were performed under tough conditions in which the tags were stretched, for instance, or exposed to high humidity and washing. Our results show that the tags can perform well when worn on-body in a harsh environment.This thesis provides several integrated solutions for wireless wearable devices. By different RFID antenna design and fabrication methods, the RFID tag can be used as the moisture and strain sensor with lightweight, small size, flexible pattern and great dailyuse reliability

Reliability Testing on Wearable Textile-Based UHF RFID Tags

Due to their huge future potential in identification, monitoring, and sensor applications, textile-integrated radio-frequency identification (RFID) tags have been an active topic of research during the recent years. A passive, battery-free RFID tag is composed of an antenna and an integrated circuit (IC) and, when integrated into a textile material, offers a cheap, unobtrusive, and completely maintenance-free wireless platform for versatile body-centric systems. One of the key challenges to be addressed, before the large-scale deployment of these textile RFID components, is their ability to withstand continuous washing, which has been found to be a major reliability issue and is currently actively studied. This thesis presents a washing reliability study of passive UHF RFID textile tags with three different coating materials. The tag antennas were fabricated by brush-painting silver ink on a 100 % cotton fabric. After attaching the ICs, the ready RFID tags were fully coated with three different protective coating materials: regular textile glue, white epoxy coating, and silicone rubber. The coated tags were washed 15 times in a household washing machine and tested wirelessly after each washing cycle for the total of 15 washing cycles. Before washing, all tags exhibited good performance and attainable read ranges of about 10 meters, under the European RFID emission regulation. Based on the reliability test and the done measurements, all three protective coating materials can successfully protect the RFID tags from the effects of washing and especially the textile glue was found to be suitable coating for the brush-painted tags. Silicon rubber also can be said as a suitable coating. White epoxy glue coating does make the tags water resistant but it is constantly losing its ability of protection after each washing cycle and, in the long run, it can be said that it does not make the tags washable