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- 3D printed lens antenna for wireless power transfer at Ku-bandPublication . Gonçalves, Ricardo; Pinho, Pedro; Carvalho, NunoIn this paper we present the design of an antenna, operating in the Ku-band, conceived for wireless power transfer systems. It comprises an hemispherical dielectric lens, fabricated using 3D printing technology, fed by a microstrip patch antenna array. The conjugation of the dielectric lens with the microstrip patch array allows the development of a compact high gain antenna. The antenna presents a matched bandwidth between 12.7 and 13.15 GHz and a maximum gain of 18.1 dBi at each element.
- Beam steering antenna and network design for WPT applicationsPublication . Costa, Andreia; Gonçalves, Ricardo; Pinho, Pedro; Carvalho, NunoThe Internet of Things (IoT) is increasingly present in our daily routine. It allows to use technology in a more efficient way. Important enabler of it is Wireless Power Transmission (WPT) as an alternative to electrical conductors (wires and cables). Given these aspects a linear microstrip antenna array was developed for 2.45 GHz ISM band, with Circular Polarization (CP). The main objective of this array is to create a beam to power up wireless sensors within a specific area of a room. The steering performance of the antenna is simulated using CST tool. Simulation results are found to be in good agreement with measurements.
- 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.
- Wireless energy transfer: dielectric lens antennas for beam shaping in wireless power-transfer applicationsPublication . Gonçalves, Ricardo; Carvalho, Nuno; Pinho, PedroIn the current contest of wireless systems, the last frontier remains the cut of the power cord. In that sense, the interest over wireless energy transfer technologies in the past years has grown exponentially. However, there are still many challenges to be overcome in order to enable wireless energy transfer full potential. One of the focus in the development of such systems is the design of very-high-gain, highly efficient, antennas that can compensate for the propagation loss of radio signals over the air. In this paper, we explore the design and manufacturing process of dielectric lenses, fabricated using a professional-grade desktop 3D printer. Lens antennas are used in order to increase beam efficiency and therefore maximize the efficiency of a wireless powertransfer system operating at microwave frequencies in the Ku band. Measurements of two fabricated prototypes showcase a large directivity, as predicted with simulations.
- 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.
- Antenna design for ultra-compact Bluetooth devicesPublication . Pereira, Felisberto; Pinho, Pedro; Gonçalves, Ricardo; Carvalho, Nuno; Lobato, João; Lopes, Sérgio I.This paper presents a solution for an ultra-compact antenna for small Bluetooth devices. The work considers the battery and the electronic components influence in the antenna design process for a real device, i.e. a Bluetooth tracker. Three different models for representing the battery and the main electronic components are studied: (i) a simple model that represents both battery and components by a ground plane; (ii) a model that represents the battery realistically and the components by a ground plane and (iii) a model that represents realistically both battery and components.
- 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.
- 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.
- Design of UAV and ground station antenas for communications link budget improvementPublication . Costa, Andreia; Gonçalves, Ricardo; Pinho, Pedro; Carvalho, NunoThis paper presents the design and implementation of two antennas aiming the improvement of the link budget between an Unmanned Aerial Vehicle (UAV) and the ground station. The performance of the antennas is simulated using CST software tool and the simulation results are found to be in good agreement with the measurements. The UAV antenna presents 6 dBi of gain with an omni-directional coverage. The ground station antenna is a directional antenna based on a stacked configuration allowing an increase of the bandwidth while achieving a gain of 13.5 dBi. Both antennas operate at 1.335 GHz and a range of 50 Km is predicted when included in the communication system.