Loading...
24 results
Search Results
Now showing 1 - 10 of 24
- 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.
- Smart environment technology as a possible enabler of smart citiesPublication . Gonçalves, Ricardo; Carvalho, Nuno Borges; Pinho, Pedro; Roselli, LucaThis paper discusses the technology of smart floors as a enabler of smart cities. The discussion will be based on technology that is embedded into the environment that enable location, navigation but also wireless power transmission for powering up elements siting on it, typically mobile devices. One of those examples is the smart floor, this implementation follows two paths, one where the floor is passive, and normally passive RFID's are embedded into the floor, they are used to provide intelligence into the surrounding space, this is normally complemented with a battery powered mobile unit that scans the floor for the sensors and communicates the information to a database which locates the mobile device in the environment. The other path for the smart city enabler is where the floor is active and delivers energy for the objects standing on top of it. In this paper these two approaches will be presented, by discussing the technology behind it. © 2014 IEEE.
- Dissipation factor and permittivity estimation of dielectric substrates using a single microstrip line measurementPublication . Gonçalves, Ricardo; Magueta, Roberto; Pinho, Pedro; Carvalho, NunoThe knowledge of the dielectric properties of materials, for the design of several components and circuits at high frequencies, is mandatory. In this paper, we present a simple method for the estimation of the dissipation factor (loss tangent) of dielectric materials based on the reflection measurement of a single microstrip line, which is applied to some common known materials, such as FR-4 and Rogers RO3010 laminates. The obtained results match well with the data on the literature for the considered materials.
- RFID-based wireless passive sensors utilizing cork materialsPublication . Gonçalves, Ricardo; Rima, Sergi; Magueta, Roberto; Pinho, Pedro; Collado, Ana; Georgiadis, Apostolos; Hester, Jimmy; Carvalho, Nuno Borges; Tentzeris, Manos M.This paper presents the design of low-cost, conformal UHF antennas and RFID tags on two types of cork substrates: 1) natural cork and 2) agglomerate cork. Such RFID tags find an application in wine bottle and barrel identification, and in addition, they are suitable for numerous antenna-based sensing applications. This paper includes the high-frequency characterization of the selected cork substrates considering the anisotropic behavior of such materials. In addition, the variation of their permittivity values as a function of the humidity is also verified. As a proof-of-concept demonstration, three conformal RFID tags have been implemented on cork, and their performance has been evaluated using both a commercial Alien ALR8800 reader and an in-house measurement setup. The reading of all tags has been checked, and a satisfactory performance has been verified, with reading ranges spanning from 0.3 to 6 m. In addition, this paper discusses how inkjet printing can be applied to cork surfaces, and an RFID tag printed on cork is used as a humidity sensor. Its performance is tested under different humidity conditions, and a good range in excess of 3 m has been achieved, allied to a good sensitivity obtained with a shift of >5 dB in threshold power of the tag for different humid conditions.
- 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.
- 3D antenna for wireless power transmission aperture coupled microstrip antenna with dielectric lensPublication . Dias, Gonçalo; Pinho, Pedro; Gonçalves, Ricardo; Carvalho, NunoNowadays 3D printers are useful for the development and rapid prototyping of dielectric structures for radiation manipulation and support of antennas. This is possible since the materials used in this machines are essentially dielectric. These can be used as radiating elements (dielectric resonators), as radiation handlers (lenses) or as a supporting base for applying conductive material to radiation (substrates). In this paper we explore 3D printing technology to develop a lens antenna for wireless power transfer operating at 20 GHz. The design, simulation and measurement of an aperture coupled microstrip antenna with dielectric lens is presented and discussed. The lens is used to focus the beam of lower gain feed antenna to produce a highly directive pattern with low side lobe.
- 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.
- RFID passive tag antenna for cork bottle stopperPublication . Gonçalves, Ricardo; Magueta, Roberto; Pinho, Pedro; Carvalho, Nuno BorgesIn this paper we propose a possible design for a RFID tag antenna embedded into cork. The antenna is small and conformal and intended to be used into bottle stoppers for tracking and logging purposes of wine or other beverages. The proposed design is based on an inductive ring and an added resistance in order to modify the current distributions of the antenna. The resulting antenna has a relatively directive radiation pattern and despite the small efficiency it is able to operate with a commercial RFID reader at a reasonable distance. © 2014 IEEE.
- Parasitic stacked slot patch antenna for DTT energy harvestingPublication . Moura, Tiago; Brás, Luís; Pinho, Pedro; Carvalho, Nuno; Gonçalves, RicardoIn this paper a rectangular patch antenna with two slots, integrated with a stacked parasitic antenna, is presented. These techniques allow a bandwidth (BW) and gain enhancement, two of the major limitations of traditional patch antennas. The antenna is designed to operate at 754 MHz for energy harvesting applications, from the Portuguese Digital Terrestrial Television (DTT) signal. The measured antenna BW is 22.5 MHz, representing an enhancement of around 17 MHz in respect to the simulated BW of the corresponding single patch configuration.
- «
- 1 (current)
- 2
- 3
- »