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- Smart Coat with a Fully-Embedded Textile Antenna for IoT ApplicationsPublication . Loss, Caroline; Goncalves, Ricardo; Lopes, Catarina; Pinho, Pedro; Salvado, RitaThe 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.
- Textile antenna for bio-radar embedded in a car seatPublication . Loss, Caroline; Gouveia, Carolina; Salvado, Rita; Pinho, Pedro; Vieira, JoséA bio-radar system is presented for vital signs acquisition, using textile antennas manufactured with a continuous substrate that integrates the ground plane. Textile antennas were selected to be used in the RF (Radio Frequency) front-end, rather than those made of conventional materials, to further integrate the system in a car seat cover and thus streamline the industrial manufacturing process. The development of the novel substrate material is described in detail, as well as its characterization process. Then, the antenna design considerations are presented. The experiments to validate the textile antennas operation by acquiring the respiratory signal of six subjects with different body structures while seated in a car seat are presented. In conclusion, it was possible to prove that bio-radar systems can operate with textile-based antennas, providing accurate results of the extraction of vital signs.
- Influence of some structural parameters on the dielectric behavior of materials for textile antennasPublication . Loss, Caroline; Gonçalves, Ricardo; Pinho, Pedro; Salvado, RitaKnowledge of the electromagnetic properties of textile materials is crucial in order to design wearable antennas. Despite the growth of research studies on textile antennas, the accurate characterization of the dielectric properties of the materials is still a challenge due to the intrinsic inhomogeneity and deformability of textiles. In this work, 11 textile materials were characterized using the resonator-based experimental technique. The results obtained using this method have shown that when positioning the roughest face of the Material Under Test (MUT) in contact with the resonator board, the extracted dielectric constant (ɛr) value is lower than the one extracted with this face positioned upside-down. Based on this observation, superficial properties of textiles were investigated. Thus, this paper relates the results of the dielectric characterization to some structural parameters of textiles, such as surface roughness and surface and bulk porosity. The results show that both surface roughness and surface porosity of the samples influence the measurements, through the positioning of the probes. Further, the influence of the positioning of the dielectric material on the performance of textile microstrip antennas was analyzed. For this, 12 prototypes of microstrip patch antennas were developed and tested. The results show that, despite the differences obtained in the characterization when placing the face or reverse-sides of the MUT in contact with the resonator board, the obtained average result of ɛr is well suited to design antennas, ensuring a good performance.
- Design and evaluation of multi-band RF energy harvesting circuits and antennas for WSNsPublication . Borges, Luís M.; Barroca, Norberto; Saraiva, Henrique M.; Tavares, Jorge; Gouveia, Paulo T.; Velez, Fernando J.; Loss, Caroline; Salvado, Rita; Pinho, Pedro; Gonçalves, Ricardo; Carvalho, Nuno Borges; Chavez-Santiago, Raúl; Balasingham, IlangkoRadio frequency (RF) energy harvesting is an emerging technology that will enable to drive the next generation of wireless sensor networks (WSNs) without the need of using batteries. In this paper, we present RF energy harvesting circuits specifically developed for GSM bands (900/1800) and a wearable dual-band antenna suitable for possible implementation within clothes for body worn applications. Besides, we address the development and experimental characterization of three different prototypes of a five-stage Dickson voltage multiplier (with match impedance circuit) responsible for harvesting the RF energy. Different printed circuit board (PCB) fabrication techniques to produce the prototypes result in different values of conversion efficiency. Therefore, we conclude that if the PCB fabrication is achieved by means of a rigorous control in the photo-positive method and chemical bath procedure applied to the PCB it allows for attaining better values for the conversion efficiency. All three prototypes (1, 2 and 3) can power supply the IRIS sensor node for RF received powers of -4 dBm, -6 dBm and -5 dBm, and conversion efficiencies of 20, 32 and 26%, respectively. © 2014 IEEE.
- Influence of the laminating manufacturing technique on the S11 parameter of printed textile antenasPublication . Loss, Caroline; Salvado, Rita; Gonçalves, Ricardo; Pinho, PedroThis paper describes the influence of the laminating technique normally used to produce printed textile antennas on their return loss (S-11) parameter. The cutting technique and the use of steam on the ironing process of conductive fabrics are considered. The surface roughness and superficial porosity of dielectric materials are analyzed. This paper concludes that despite the unwanted compression applied on the laminating process, the technique is well suited to fabricated printed antennas.
- Different antenna designs for non-contact vital signs measurement: a reviewPublication . Gouveia, Carolina; Loss, Caroline; Pinho, P.; Vieira, JoséCardiopulmonary activity measured through contactless means is a hot topic within the research community. The Doppler radar is an approach often used to acquire vital signs in real time and to further estimate their rates, in a remote way and without requiring direct contact with subjects. Many solutions have been proposed in the literature, using different transceivers and operation modes. Nonetheless, all different strategies have a common goal: enhance the system efficiency, reduce the manufacturing cost, and minimize the overall size of the system. Antennas are a key component for these systems since they can influence the radar robustness directly. Therefore, antennas must be designed with care, facing several trade-offs to meet all the system requirements. In this sense, it is necessary to define the proper guidelines that need to be followed in the antenna design. In this manuscript, an extensive review on different antenna designs for non-contact vital signals measurements is presented. It is intended to point out and quantify which parameters are crucial for the optimal radar operation, for non-contact vital signs' acquisition.
- Influence of some structural parameters on the dielectric behavior of materials for textile antennasPublication . Loss, Caroline; Gonçalves, Ricardo; Pinho, Pedro; Salvado, RitaKnowledge of the electromagnetic properties of textile materials is crucial in order to design wearable antennas. Despite the growth of research studies on textile antennas, the accurate characterization of the dielectric properties of the materials is still a challenge due to the intrinsic inhomogeneity and deformability of textiles. In this work, 11 textile materials were characterized using the resonator-based experimental technique. The results obtained using this method have shown that when positioning the roughest face of the Material Under Test (MUT) in contact with the resonator board, the extracted dielectric constant (e(r)) value is lower than the one extracted with this face positioned upside-down. Based on this observation, superficial properties of textiles were investigated. Thus, this paper relates the results of the dielectric characterization to some structural parameters of textiles, such as surface roughness and surface and bulk porosity. The results show that both surface roughness and surface porosity of the samples influence the measurements, through the positioning of the probes. Further, the influence of the positioning of the dielectric material on the performance of textile microstrip antennas was analyzed. For this, 12 prototypes of microstrip patch antennas were developed and tested. The results show that, despite the differences obtained in the characterization when placing the face or reverse-sides of the MUT in contact with the resonator board, the obtained average result of e(r) is well suited to design antennas, ensuring a good performance.
- Textile antenna array for bio-radar applicationsPublication . Gouveia, Carolina; Loss, Caroline; Raida, Zbynek; Lacik, Jaroslav; Pinho, Pedro; Vieira, JoséIn this paper, a 2 x 2 antenna array operating at 5.8 GHz is presented for vital signs acquisition using a radar-based system, also known as bio-radar. Since these non-contact systems have multiple applications, their front-end design should take into account the monitoring environment of each specific application. In this sense, the antenna design has a crucial role to guarantee the proper integration of the full system, considering different materials. In this work, the antennas were made using textile materials, in order to integrate the bio-radar system in a car seat cover. This work presents the design of the antenna and the results achieved through measures in the anechoic chamber. Furthermore, respiratory signals were also acquired with the manufactured antennas and they are herein presented for validation purposes.
- Textile antenna for first-person view gogglesPublication . André, Luís; Pinho, Pedro; Gouveia, Carolina; Loss, CarolineUnmanned Aerial Vehicles, also known as drones, are vehicles controlled remotely. First-Person View (FPV) technology allows these vehicles to have greater versatility and be more easily piloted. The antennas currently used for video transmission are bulky and uncomfortable, so there is a need for this volume to be reduced to increase portability, being this the focus of the paper. The antenna was developed in textile materials to reduce its size and weight, as these materials allow for a better comfort and a reduced footprint. This paper presents a microstrip array adapted for the frequencies used in FPV video transmission. The designed textile antenna was compared with a commercially available rigid antenna used for this transmission. The comparison shows promising results for the antenna made of textile materials. The main goal of increasing the comfort and portability of the FPV goggles was achieved.
- Textile antenna for RF energy harvesting fully embedded in clothingPublication . Loss, Caroline; Gonçalves, Ricardo; Lopes, Catarina; Salvado, Rita; Pinho, PedroIn the context of Wireless Body Sensor Networks for healthcare and pervasive applications, textile antennas allow an ubiquitous monitoring, communication, energy harvesting and storage. This paper presents a smart coat with a dual-band textile antenna for Radio Frequency (RF) energy harvesting, operating at GSM 900 and DSC 1800 bands, which is fully embedded in the garment. Results obtained before and after the integration of the antenna into the garment are compared. The gain obtained in the simulation is about 1.8 dBi and 2.06 dBi, with radiation efficiency of 82% and 77,6% for the lowest and highest operating frequency bands, respectively.