In the broad context of Wireless Body Sensor Networks for healthcare and pervasive applications, the design of wearable antennas offers the possibility of ubiquitous monitoring, communication and energy harvesting and storage. Specific requirements for wearable antennas are a planar structure and flexible construction materials. Several properties of the materials influence the behaviour of the antenna. For instance, the bandwidth and the efficiency of a planar microstrip antenna are mainly determined by the permittivity and the thickness of the substrate. The use of textiles in wearable antennas requires the characterization of their properties. Specific electrical conductive textiles are available on the market and have been successfully used. Ordinary textile fabrics have been used as substrates. However, little information can be found on the electromagnetic properties of regular textiles. Therefore this paper is mainly focused on the analysis of the dielectric properties of normal fabrics. In general, textiles present a very low dielectric constant that reduces the surface wave losses and increases the impedance bandwidth of the antenna. However, textile materials are constantly exchanging water molecules with the surroundings, which affects their electromagnetic properties. In addition, textile fabrics are porous, anisotropic and compressible materials whose thickness and density might change with low pressures. Therefore it is important to know how these characteristics influence the behaviour of the antenna in order to minimize unwanted effects. This paper presents a survey of the key points for the design and development of textile antennas, from the choice of the textile materials to the framing of the antenna. An analysis of the textile materials that have been used is also presented.

Abstract-A wideband half-mode substrate-integratedwaveguide cavity-backed slot antenna covering all Unlicensed National Information Infrastructure (U-NII) radio bands (5.15 GHz-5.85 GHz) is designed, fabricated and validated. By a half-mode implementation of a multi-moded cavity with nonresonant slot, a compact ultra-wideband antenna is obtained with very stable radiation characteristics, owing to the excellent antenna/platform isolation. Cork material is applied as antenna substrate, making the proposed antenna suitable for integration into floors or walls. In free-space conditions, an impedance bandwidth of 1.30 GHz (23.7 %), a radiation efficiency of 85 %, a front-to-back ratio of 15.0 dB and a maximum gain of 4.3 dBi at 5.50 GHz are measured. Performance is also validated when the antenna is deployed on various dielectric or conducting platforms and underneath different dielectric superstrates. Only the latter slightly detunes the antenna's impedance bandwidth. Yet, the complete frequency band of interest remains covered, owing to additional design margins incorporated in the requirements. Its compactness, unobtrusive integration potential and stable high performance in different environments make this antenna topology an ideal candidate for Internet of Things applications.

The Internet of Things (IoT) scenario is strongly related with the advance of the development of wireless sensor networks (WSN) and radio frequency identification (RFID) systems. Additionally, in the WSN context, for a continuous feed, the integration of textile antennas for energy harvesting into smart clothing is a particularly interesting solution when the replacement of batteries is not easy to practice, such as in wearable devices. This paper presents the E-Caption: Smart and Sustainable Coat. It has an embedded dual-band textile antenna for electromagnetic energy harvesting, operating at global system for mobile communication (GSM) 900 and digital cellular system (DCS) 1800 bands. This printed antenna is fully integrated, as its dielectric is the textile material composing the coat itself. The E-Caption illustrates the innovative concept of textile antennas that can be manipulated as simple emblems. Seven prototypes of these “emblem” antennas, manufactured by lamination and embroidering techniques are also presented. It is shown that the orientation of the conductive fabric does not influence the performance of the antenna. It is also shown that the direction and number of the stitches in the embroidery may influence the performance of the antenna. Moreover, the comparison of results obtained before and after the integration of the antenna into cloth shows the integration does not affect the behavior of the antenna.