Loading...
6 results
Search Results
Now showing 1 - 6 of 6
- 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.
- 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.
- Development of a textile antenna using a continuous substrate integrating the ground planePublication . Loss, Caroline; Salvado, Rita; Gonçalves, Ricardo; Pinho, PedroThe exponential growth in the wearable market is boosting the industrialization process of manufacturing textile antennas. The patch of the printed antennas can be easily cut, embroidered or screen printed by machines. The conception of an optimal industrial substrate that meets all the mechanical and electromagnetic requirements is still a challenge. This paper presents a printed textile antenna for ISM band using a continuous Substrate Integrating the Ground Plane (SIGP). The SIGP is a novel textile material, which is a double fabric that integrates the dielectric substrate and the conductive ground plane in a single textile.