Wearable antennas and electronics technology rapidly grows the last decades and leads to a future where smart textiles will be integrated into our garments. However the wearable technology research includes unsolved or of different approach challenges. This thesis deals with challenges regarding wearable antenna characterization and measurements, textile antennas feeding and textile transmission lines interconnecting. Regarding the wearable antenna characterization and measurements, a novel design of a liquid torso phantom and a new methodology for evaluating wearable antenna performance by using the cylindrical near field measurement technique are proposed. As for the textile antennas and transmission lines feeding and interconnecting, two novel methods are proposed.

No description available.

abstract: Flexibility, reconfigurability and wearability technologies for antenna designs are presented, investigated and merged in this work. Prior to the design of these radiating elements, a study is conducted on several flexible substrates and how to fabricate flexible devices. Furthermore, the integration of active devices into the flexible substrates is also investigated. A new approach of designing inkjet-printed flexible reconfigurable antennas, based on the concept of printed slot elements, is proposed. An alternate technique to reconfigure the folded slot antenna is also reported. The proposed radiator works for both Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The flexible reconfigurable antenna is also redesigned to resonate at both (2.4/5.2 GHz) for WLAN devices and its Multiple-Input Multiple-Output (MIMO) configuration is reported. Two orthogonal elements are used to form the MIMO antenna system for better isolation. The wearability of the proposed flexible reconfigurable radiator is also discussed. Since wearable antennas operate close to the human body, which is considered as a lossy tissue, an isolation between the radiating elements and human body is required to improve the radiation characteristics and to reduce the Specific Absorption Rate (SAR). The proposed antenna is redesigned on an Artificial Magnetic Conductor (AMC) surface that also functions as a ground plane to isolate the radiator from the human body. To examine its performance as a body-worn device, it is measured at different positions on the human body. Furthermore, simulations show that the SAR level is reduced when using the AMC surface. The proposed wearable antenna works for both Wireless Body Area Network (WBAN) and WiMAX body-worn wireless devices. Electromagnetic bandgap (EBG) structures are used to suppress surface wave propagation in printed antennas. However, due to the presence of vias, not all of them can be utilized in flexible radiators. Thus, a Perforated High Impedance Surface (PHIS) is proposed which suppresses the surface waves without the need of vias, and it also serves as a ground plane for flexible antennas. The surface wave suppression and the antenna applications of the proposed PHIS surface are discussed. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

This thesis provides novel contribution to the field of body-centric wireless communications (BCWC) with the development of a measurement methodology for wearable antenna characterisation on the human body, the implementation of fully-textile wearable antennas and the on-body channel modelling considering different antenna types and user's dynamic effects. More specifically, a measurement methodology is developed for characterising wearable antennas on different locations of the human body. A cylindrical near-field (CNF) technique is employed, which facilitates wearable antenna measurements on a full-body solid anthropomorphic mannequin (SAM) phantom. This technique allows the fast extraction of the full spherical radiation pattern and the corresponding radiation efficiency, which is an important parameter for optimising wearable system design. It appears as a cost- effective and easy to implement solution that does not require expensive positioning systems to rotate the phantom, in contrast to conventional roll-over-azimuth far-field systems. Furthermore, a flexible fully-textile wearable antenna is designed, fabricated and measured at 2.4 GHz that can be easily integrated in smart clothing. It supports surface wave propagation and exhibits an omni-directional radiation pattern that makes it suitable for on-body communications. It is based on a multilayer low-profile higher-mode patch antenna (HMMPA) design with embroidered shorting vias. Emphasis is given to the fabrication process of the textile vias with conductive sewing thread that play an important role in generating the optimal mode for on-body radiation. The radiation pattern shape of the proposed fully-textile antenna was found to be similar to a copper rigid antenna, exhibiting a high on-body radiation efficiency of 50 %. The potential of the embroidery technique for creating wearable antennas is also demonstrated with the fabrication of a circularly polarised spiral antenna that achieves a broadband performance from 0.9-3 GHz, which is suitable for off-body communications. By testing the textile spiral antenna on the SAM phantom, the antenna-body interaction is examined in a wide frequency range. Finally, a statistical characterisation of on-body communication channels is undertaken both with EM simulations and channel measurements including user's dynamic movement (walking and running). By using antenna types of different polarisation, the on-body channels are examined for different propagation conditions. Four on-body channels are examined with the one part fixed on the waist of the human body while the other part located on the chest, back, wrist and foot. Channel path gain is derived, while large-scale and small-scale fading are modelled by best-fit statistical distributions.

SmartWatches are watches with the property that they can connect to internet.The interest and market for smartwatches has increased remarkably over the pastfew years. However, most of today's solutions cover only the frequency bandsBluetooth (BT) and Global Positioning System(GPS). A desired property of thenext generation of smartwatches is to include additional frequency bands suchas Global System for Mobile Communication(GSM) and Third Generation (3G)cellular bands, so that the Smart Watch can become independent of a smartphone.This sets new challenges for antenna design in small regions. The limited sizetogether with the increased bandwidth demand causes the major problem.The purpose of this thesis is to investigate the antenna concept for wrist wear-able devices that has earlier been developed by the RF team at Sunway Commu-nication AB in Stockholm. The main objective of this project is to study howthis antenna concept can be changed to achieve a given set of requirements onfrequency, bandwidth and eciency. Characteristic Mode Analysis and antennaquality factor calculated from the input impedance, are tools used to help under-stand and improve the characteristics of the antenna.A decomposition method and a parametric study were initially applied to theplanar version of the antenna concept. We investigated then the inuence of theposition of the feeds and the slot that separates the two antenna elements. Anoptimised design of the planar antenna was achieved based on the results fromthose studies. Four prototypes of this antenna were built and measured in the RFlaboratory in Kista.The possibility of miniaturization was studied through simulations by analysingthe eect of using a higher dielectric constant material in the antenna. Two dif-ferent arrangements were investigated. The eect of bending the antenna to t ona human wrist was also investigated, where a frequency shift was observed in theresults. The change in bandwidth of the dierent modes is related to the changein the stored energy of the antenna caused by the bending.We made a prototype of the planar antenna that shows a good agreement withsimulation results and fulls the basic requirements on frequency, bandwidth andeciency. We also found that the addition of a shorting pin showed a bandwidthimprovement of the high-band port and we showed through simulation that it ispossible to reduce the size of the antenna by adding a layer of PCABS material.

Wearable technology has attracted global attention in the last decade and the market is experiencing an unprecedented growth. Wearable devices are designed to be low-profile, light-weight and integrated seamlessly into daily life. Comfort is one of the most important requirements for wearable devices. Fabric based antennas are soft, flexible and can be integrated into clothing. State of the art textile manufacturing techniques such as embroidery, combined with advanced conductive textile materials can be used to fabricate flexible fabric based on-body antennas. In this thesis, the feasibility of using computerised embroidery in the fabrication of wearable, flexible yet functional fabric based antennas have been examined. The fabric based antennas are embroidered using conductive threads. The most suitable materials for fabricating embroidered antennas have been identified. The embroidered fabric based antenna systems including transmission lines and low-profile detachable connectors have been fabricated and their RF performances have been tested. The optimal manufacturing parameters related to embroidery such as stitch direction, spacing and length have been examined. The repeatability of embroidered antennas, cost estimation, and complexity of manufacturing process have been clearly presented. The results can be used to inform and provide guidelines for the development of representative products that can be mass manufactured. A new simulation approach has been introduced to analyse the anisotropic properties of embroidered conductive threads. Simulations and measurements indicate that the performances of embroidered antennas are affected by the anisotropic surface current due to the embroidered stitches. Exploiting the current direction, a novel non-uniform meshed patch antenna has been designed. Representative results show that the non-uniform meshed structure can significantly reduce more than 75% of the usage of conductive materials for the microstrip antennas with negligible effect on the antenna performance.

In this age of wireless technology, Body Area networks (BAN) is revolutionising the concept of patient care and health monitoring. BAN provides people good assessment of their health status at any time, wherever they are physically. The increased interest in developing effective body (in, on & off) communication systems made phantoms which can mimic the electrical properties of an actual human body necessary. Wearable antennas which are the indispensable part of BAN got to be low pro file and above all influences that human body can make. There should also be a way to reduce the effect of antennas on human body namely specific absorption rate (SAR). In this work effort has been made to develop phantoms suitable for both On body and In body communications. The base materials which are selected for the study are of biological origin (bio ceramics and biopolymers) whose behaviour is closer to that of human tissues. As these phantoms are biocompatible they are essentially non toxic where the conventionally available phantoms are toxic in nature. Different kinds of low profile conformal wearable antennas working at 2.4GHz ISM band were developed and studied in the BAN perspective. Antennas suffer much in terms of matching and efficiency when they are in contact or in the premises of human body. This is a major hurdle in the way to setting up a good body communication network. This work encompasses various techniques adopted to limit the body interferences to an acceptable level. The techniques adopted (Such as Backing Ground Plane, High Impedance Surface & Polymeric Ferrite Sheets) proved to be effective in reducing the sway in antenna characteristics when they are mounted on body. Specific absorption rate is also brought to acceptable levels and thus avoiding the formation of hot spots due to microwave absorption. A safer and cost effective BAN can be set up using this work which will lead to a safer, mobile and healthy future. / Les réseaux BAN (Body Area Network) révolutionnent le concept de la surveillance et de la prise en charge à distance de la santé du patient. Le BAN fournit des informations sur l’état de santé du patient en temps réel quelque soit l’endroit où il se trouve. Dans le « télé monitoring », des capteurs de mouvement, de respiration ou du rythme cardiaque placés à l’intérieur ou sur le corps humain transmettent des données via le réseau sans fil constituant le BAN, une antenne étant associée à chaque nœud du réseau. La communication peut être in/on, on/on ou on/off selon que les antennes sont placées à l’intérieur, sur ou à l’extérieur du corps. Le développement des BAN nécessite la réalisation de modèles (ou fantômes) simulant au mieux les propriétés électromagnétiques du corps humain. Des antennes portables, miniaturisées doivent être réalisées avec des contraintes d’intégration d’une part (aux vêtements, à des objets type montre ou badge), des contraintes de résistance ou de prise en compte de l’influence du corps d’autre part. La réduction de l’impact des antennes sur les tissus en terme de SAR (Specific Absorption Rate) doit également être considérée. Dans ce travail, l’objectif est de développer des fantômes valables pour les communications dans et sur le corps. Les matériaux de base sélectionnés sont d’origine biologique (biocéramiques et biopolymères) avec des propriétés proches de celles des tissus humains. Ces fantômes étant biocompatibles, ils sont essentiellement non toxiques alors que les fantômes usuels le sont en général. D’autre part, différents types d’antennes conformables, fonctionnant dans la bande ISM 2.4 GHz ont été développées et étudiées dans la perspective du BAN. Les antennes voient leur adaptation et leur efficacité chuter au contact ou à proximité du corps, ce qui constitue un écueil majeur pour établir une bonne communication. Différentes méthodes permettant de réduire l’influence du corps (plan de masse à l’arrière, surface haute impédance, feuille de ferrite polymère) sont testés et leurs avantages et inconvénients développés. Des mesures de SAR permettent aussi de démontrer l’efficacité de ces méthodes sur la réduction de la puissance absorbée par les tissus. Au final, ce travail apporte une contribution à l’étude théorique et expérimentale de l’interaction entre corps humain et antenne dans le cadre des réseaux BAN appliqués à la télésurveillance de la santé.