ISEL - Engenharia Electrónica, Telecomunicações e Computadores
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- A 3-phase model for VIS/NIR mu C-Si : H p-i-n detectorsPublication . Vieira, Manuela; Fantoni, Alessandro; Fernandes, Miguel; Maçarico, António Filipe Ruas Trindade; Schwarz, R.The spectral response and the photocurrent delivered by entirely microcrystalline p-i-n-Si:H detectors an analysed under different applied bias and light illumination conditions. The spectral response and the internal collection depend not only on the energy range but also on the illumination side. Under [p]- and [n]-side irradiation, the internal collection characteristics have an atypical shape. It is high for applied bias and lower than the open circuit voltage, shows a steep decrease near the open circuit voltage (higher under [n]-side illumination) and levels off for higher voltages. Additionally, the numerical modeling of the VIS/NIR detector, based on the band discontinuities near the grain boundaries and interfaces, complements the study and gives insight into the internal physical process.
- 3D antenna array for SWIPT Sensing with WPT capabilitiesPublication . Pires, Diogo; Belo, Daniel; Jordão, Marina; Pinho, Pedro; Carvalho, NunoIn this work, the design and development of an alternative three-dimensional array is presented. This arrangement aims to improve Simultaneously Wireless Information and Power Transfer (SWIPT) systems and to provide advantages when integrated into a Wireless Sensor Network (WSN) architecture. The conceived 3D antenna array consists of eight antenna elements operating at 5.65 GHz that are attached in a 3D printed heptagonal prism. With this structure, it is intended to achieve as close as possible to an omnidirectional radiation pattern with considerable gain, avoiding power losses. The experimental measurements carried out are in line with the performed electromagnetic simulations and validate the array operation. A full azimuth coverage was ensured with an average realized gain of 6.7 dBi. For some azimuth directions, this gain can reach approximately 8.35 dBi. This array proves to be a reliable solution to fed multiple low-power sensors that are placed over the 360 azimuth angles.
- 3D antenna characterization for WPT applicationsPublication . Jordão, Marina; Pires, Diogo; Belo, Daniel; Pinho, Pedro; Carvalho, Nuno BorgesThe main goal of this paper is to present a three-dimensional (3D) antenna array to improve the performance of wireless power transmission (WPT) systems, as well as its characterization with over-the-air (OTA) multi-sine techniques. The 3D antenna consists of 15 antenna elements attached to an alternative 3D structure, allowing energy to be transmitted to all azimuth directions at different elevation angles without moving. The OTA multi-sine characterization technique was first utilized to identify issues in antenna arrays. However, in this work, the technique is used to identify which elements of the 3D antenna should operate to transmit the energy in a specific direction. Besides, the 3D antenna design description and its characterization are performed to authenticate its operation. Since 3D antennas are an advantage in WPT applications, the antenna is evaluated in a real WPT scenario to power an RF-DC converter, and experimental results are presented.
- 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.
- 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.
- 5.8 GHz Microstrip antennas and array for microwave power transferPublication . Carvalho, António; Carvalho, Nuno; Pinho, Pedro; Georgiadis, Apostolos; Constanzo, AlessandraWireless power transmission presents itself as being a solution to some common problems of the extensive use of electronic devices such as the removal of parasitic components present in feeding pads and the constant charge of electronic devices without the need of wires. This solution becomes attractive, for example, as a means of increasing the flight time of battery dependent unmanned aerial vehicles. Microstrip antenna due to their ease of manufacturing, low fabrication cost, support of different polarizations and conformability to irregular surfaces and different substrates, seem very advantageous in being used for microwave power transmission. This paper presents a linearly polarized 16-element antenna array with uniform amplitude and phase excitation proposed for power transmission while both a linearly and circularly polarized single element patch are proposed for reception.
- 5G-NR radio planning for connected and autonomous vehicles servicesPublication . Teixeira, Grazielle Bonaldo; Serrador, António João NunesThe 5G network development is enabling many emerge technologies as connected and autonomous vehicles (CAV), promising a significant impact in the telecommunications industry in the future. In this thesis, was performed 5G radio planning by coverage and capacity, entirely when CAV applications are provided, requiring minimum and maximum user data rates according to different services categories from 5GMOBIX project. 5G air interface was explored joint to MIMO and modulation orders configurations, intending to analyse the different results in two diverse highways around Lisbon, for urban and rural propagation environments. Vehicles traffic model was simulated using real statistic numbers, aiming to compute more effective KPIs while the radio planning. The final number of sites calculated were compared regarding to each scenario simulated as well as the number of vehicles supported for each service category. The results showed that the cell ranges reached in DL were tens of kilometres, despite of some meters in UL for some network configurations. Also, the radio resources showed being enough when minimum user data rate is required, nevertheless when maximum user data rate is required, new cell and vehicle ranges recalculation were needed, reaching much higher number of sites due to the cell capacity limitation. The number of sites required in urban environment showed being the double when comparing to rural, due to the higher vehicles traffic.
- A 5GHz/1.8V CMOS active balun integrated with LNAPublication . Azevedo, Fernando; Mendes, Luís; Fialho, Vitor; Vaz, João C.; Fortes, Fernando; Rosário, Maria J.The development of high performance monolithic RF front-ends requires innovative RF circuit design to make the best of a good technology. A fully differential approach is usually preferred, due to its well-known properties. Although the differential approach must be preserved inside the chip, there are cases where the input signal is single-ended such as RF image filters and IF filters in a RF receiver. In these situations, a stage able to convert single-ended into differential signals (balun) is needed. The most cited topology, which is capable of providing high gain, consists on a differential stage with one of the two inputs grounded. Unfortunately, this solution has some drawbacks when implemented monolithically. This work presents the design and simulated results of an innovative high-performance monolithic single to differential converter, which overcomes the limitations of the circuits.The integration of the monolithic active balun circuit with an LNA on a 0.18μm CMOS process is also reported. The circuits presented here are aimed at 802.11a. Section 2 describes the balun circuit and section 3 presents its performance when it is connected to a conventional single-ended LNA. Section 4 shows the simulated performance results focused at phase/amplitude balance and noise figure. Finally, the last section draws conclusions and future work.
- A 5GHz1.8V low power CMOS low-noise amplifierPublication . Azevedo, Fernando; Mendes, Luís; Fialho, Vitor; Vaz, João C.; Fortes, Fernando; Rosário, Maria J.Wireless local-area networks (WLANs) have been deployed as office and home communications infrastructures worldwide. The diversification of the standards, such as IEEE 802.11 series demands the design of RF front-ends. Low power consumption is one of the most important design concerns in the application of those technologies. To maintain competitive hardware costs, CMOS has been used since it is the best solution for low cost and high integration processing, allowing analog circuits to be mixed with digital ones. In the receiver chain, the low noise amplifier (LNA) is one of the most critical blocks in a transceiver design. The sensitivity is mainly determined by the LNA noise figure and gain. It interfaces with the pre-select filter and the mixer. Furthermore, since it is the first gain stage, care must be taken to provide accurate input match, low-noise figure, good linearity and a sufficient gain over a wide band of operation. Several CMOS LNAs have been reported during the last decade, showing that the most research has been done at 802.11/b and GSM standards (900-2400MHz spectrum) and more recently at 802.11/a (5GHz band). One of the more significant disadvantages of 802.11/b is that the frequency band is crowded and subject to interference from other technologies, as is 2.4GHz cordless phones and Bluetooth. As the demand for radio-frequency integrated circuits, operating at higher frequency bands, increases, the IEEE 802.11/a standard becomes a very attractive option to wireless communication system developers. This paper presents the design and implementation of a low power, low noise amplifier aimed at IEEE 802.11a for WLAN applications. It was designed to be integrated with an active balun and mixer, representing the first step toward a fully integrated monolithic WLAN receiver. All the required circuits are integrated at the same die and are powered by 1.8V supply source. Preliminary experimental results (S-parameters) are shown and promise excellent results. The LNA circuit design details are illustrated in Section 2. Spectre simulation results focused at gain, noise figure (NF) and input/output matching are presented in Section 3. Finally, conclusions and comparison with other recently reported LNAs are made in Section 4, followed by future work.
- 5GMEDE-5G mobile edge computing with enriched radio network information servicesPublication . Akman, A.; Monteiro, V.; Marques, P.; Rodriguez, J.; Vieira, Pedro; Marques, H.; Abdalla, A.5G has a number of challenges to solve. Higher data usage and processing power necessities have emerged from the increasing number of mobile users as well as mobile applications becoming more and more demanding. There is a significant need to reduce the latency of the mobile network while cutting down on energy consumption. Backhaul traffic needs to be optimized to avoid setting up costly backhaul connections. Many loT scenarios have conflicting requirements; the need for cheap and low complexity devices vs the need for processing power. Operators need to come up with value added services to avoid being dumb-pipe operators. The answer to these challenges and more require cloud-computing capabilities within the Radio :Access Network (RAN) as well as a platform for mobile operators and third-party application providers to utilize these computing capabilities. This is where Mobile Edge Computing (MEC), one of the key emerging technologies for 5G, comes into play. The 5GMEDE project proposes to not only develop and demonstrate a complete MEC solution, including the MEC framework, Base Station services and applications to run on top, but also offers innovative features like constraint based mobile edge selection, using data analytics to enrich and refine real-time radio network information and utilizing Software Defined Wireless Networks (SDWN) concepts to improve mobility and resource allocation services to enable operators.