ENIDH – EEM - Engenharia Eletrotécnica Marítima
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- A 1.1 µA voltage reference circuit with high PSRR and temperature compensationPublication . Pereira, M. Silva; Costa, João E. N.; Santos, M.; Vaz, J. CaldinhasThis paper presents a low-power and a low output voltage CMOS Bandgap Reference Generator topology with high PSRR and a novel temperature curvature compensation method. The proposed design was implemented in a standard 0.13 μm CMOS process. The main circuit is based in an opamp based β-multiplier bandgap circuit with resistive division. The compensation method cancels out up to 2nd order non-linear terms of the BJT voltage by using the MOSFET leakage current effect. The performance of the circuit was verified by post-layout simulations. Simulated results have shown temperature coefficients as low as -4.4 ppm/°C over a temperature range of 140°C (-40°C to 100°C). In addition the circuit demonstrated a PSSR of -100 dB at low frequencies and -73 dB at 1 MHz. The current consumption is 1.1 μA at 27°C.
- Accomplishing PROMISE, PROgrammable MIxed Signal ASIC Electronics FrameworkPublication . Berrojo, Luis; Veljkovic, Filip; Ayzac, Philippe; Maggioni-Mezzomo, Cecilia; Trouche, Christophe; Kakoulin, Michael; Franciscatto, Giancarlo; Berti, Laurent; Arslanov, Dmitry; Póvoa, Ricardo; Guilherme, Jorge; Roumkou, Anna; Tukkiniemi, KariThis paper presents the activities, current results and status of the PROMISE (PROgrammable MIxed Signal Electronics) project which started at the beginning of 2020 . The project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 870358. It’s tailored to bring to the space community a flexible, cost competitive mixed-signal ASIC architecture design ecosystem built on a portfolio of silicon qualified hardened IP blocks. It includes analogue IPs such as ADC, DAC, PLL, LDO, BG, LO, POR and HV MOS transistors. A digital embedded FPGA core provides a flexible programmable element and an NVM permits reconfiguration abilities without the need of using an external memory. All these elements are included on the PILOT Circuit ASIC that will be submitted to electrical validation and radiation testing as part of the qualification process of these basic elements for their future use as building blocks.
- Adiabatic radial perturbations of relativistic stars: Analytic solutions to an old problemPublication . Luz, Paulo; Carloni, SanteWe present a new system of equations that fully characterizes adiabatic, radial perturbations of perfect fluid stars within the theory of general relativity. The properties of the system are discussed, and, provided that the equilibrium spacetime verifies some general regularity conditions, analytical solutions for the perturbation variables are found. As illustrative examples, the results are applied to study perturbations of selected classical exact spacetimes, and the first oscillation eigenfrequencies are computed. Exploiting the new formalism, we derive an upper bound for the maximum compactness of stable, perfect fluid stars, which is equation-of-state agnostic and significantly smaller than the Buchdahl bound.
- Advanced sensing and information technologies for timely artefact diagnosisPublication . Chaves Ferreira, Paulo; Utkin, Andrei Borissovitch; Argyriou, Lemonia; Bexiga, Vasco; Boldrighini, Francesca; Cantoro, Gianluca; Drygiannakis, Myronas; Giapitsoglou, Kostas; Governatori, Giulia; Manataki, Meropi; Marsella, Stefano; Marzoli, Marcello; Oikonomou, Dimitris; Papadopoylos, Nikos G.; Santamaria, Ulderico; Sarris, Apostolos; Tzigounaki, Anastasia; Uckan, Eren; Vlachakis, Georgios; Williamson, Robert James; Akbas, Bulent; Cakir, Ferit
- Análise Qualitativa e Quantitativa do Cluster do Mar PortuguêsPublication . Simões, Abel; Ferreira, Ana Maria; Salvador, Regina; Soares, Carlos GuedesReconhecendo-se a importância de um Cluster do Mar para Portugal, procura-se identificar e analisar as principais relações intersetoriais que se processam no seu interior. Assim, na primeira parte é feita uma análise de carácter mais qualitativo, através da aplicação de inquéritos a empresas de transporte marítimo, estaleiros navais, portos, associações empresariais e instituições de ensino e investigação. Na segunda parte, utilizando a análise de input-output procede-se à quantificação das ligações existentes entre setores do Cluster marítimo português, ao cálculo dos coeficientes de interdependência e apresentam-se alguns dos efeitos multiplicadores das atividades marítimas. Algumas debilidades estruturais, que são comuns a outras áreas, como sejam a fraca cooperação e competição entre setores económicos e incipientes relações intersetoriais, refletem-se ao nível deste Cluster como uma das suas principais fragilidades, a ponto de comprometer o reconhecimento da sua existência na economia marítima nacional.
- Analysis and Design of Current Mode Class-D Power Amplifiers With Finite Feeding InductorsPublication . Silva-Pereira, M.; Assunção, Mário; Vaz, João CaldinhasCurrent-mode class-D (CMCD) power amplifiers (PAs) may not achieve a switching efficiency as good as class-E PAs, but they require fewer inductances and deliver almost five times more power for the same load and supply voltage when compared with the ideal push–pull class-E PA. Furthermore, CMCD PAs can easily use bondwires as the only circuit inductors, a precious feature that Internet-of-Things (IoT) wireless interfaces can exploit. For this reason, we analyze the voltage and current waveforms in CMCD PAs without assuming infinite value feeding inductors (i.e., without choke inductors). It is shown that the current stress on the switching device is significantly higher than in the conventional topology, especially in bondwire-based designs where relatively small feeding induc tances are presented. Finally, we propose a design procedure for a given feeding inductance that maximizes energy efficiency while delivering a compact-size solution. A 2.4-GHz PA capable of delivering 19.8 dBm to a 100-Ω differential load with a power added-efficiency (PAE) of 58% is presented. Three-dimensional electromagnetic (3-D EM) simulations combined with postlayout simulations were used to evaluate the PA performance in a quad-flat nonlead (QFN)-type package. The circuit is designed in a 0.13-μm process and only occupies a silicon area of 0.025 mm2.
- Architectural Design for Heartbeat Detection Circuits using Verilog-A Behavioral ModelingPublication . Vieira, R.; Passos, F.; Póvoa, R.; Martins, R.; Horta, N.; Guilherme, J.; Lourenço, N.This work presents a study of two analog frontend circuit architectures for heartbeat detection. Both circuits present an amplification block as the first stage, followed by a band-pass filter. In the first, the heartbeat detection is done using an adaptive threshold based on pulse-width, whereas the heartbeat detection in the second is done using a sample and hold to find the maximum and minimum peak of each beating. Both architectures are modeled in Verilog-A and simulated using real-world ECG signals with different characteristics. This work studies possible fundamental analog circuit blocks suitable for wearable implementation. It evaluates critical performances requirements from the analysis of the behavior simulations. It was verified that the first circuit can properly detect heartbeats as long as the input-referred noise is below 21 μV, whereas the second one ensures it until 30 μV. The low cutoff frequency can be approximately 10 Hz without compromising the signal’s peaks, which means that these specifications can be relaxed substantially compared to systems intended to reconstruct the signal accurately.
- Buckling and nonlinear response of functionally graded plates under thermo-mechanical loadingPublication . Moita, José S.; Araújo, Aurélio L.; Correia, Victor Franco; Soares, C. M. Mota; Herskovits, Josén this work, a formulation for buckling and geometrically nonlinear analysis of functionally graded plates under thermo-mechanical loading is presented. The influence of high temperature environment on deflections due to mechanical loading as well the deflections produced by thermal loads acting alone or combined with mechanical loads is analysed. The implemented finite element model is based on a non-conforming triangular flat plate/shell element, with three nodes and eight degrees of freedom per node, associated with a higher order shear deformation theory. The solutions of some illustrative examples are evaluated involving the variation of volume fractions of constituent materials, temperature range and material combinations, which have significant impact on the deflections of plates. The numerical results obtained with the present model are presented and compared with alternative solutions.
- Coefficient of Voltage Energy EfficiencyPublication . Gnaciński, P.; Mindykowski, J.; Pepliński, M.; Tarasiuk, T.; Costa, J. D.; Assunção, M.; Silveira, L.; Zakharchenko, V.; Drankova, A.; Mukha, M.; Xu, XThe reduction of greenhouse gas emissions is a major contemporary challenge. This has prompted the requirements concerning energy efficiency for ships, among other things. Improvement in eficiency of ship operations could be achieved by reducing unnecessary power consumption by induction motors. Specifically, the occurrence of power quality disturbances, such as frequency and voltage deviations, voltage unbalances, and voltage harmonics, can cause an extraordinary increase in the power losses occurring in induction motors, as well as an unnecessary increase in the output power. Furthermore, excessive power quality disturbances are often interconnected with failures of on-board equipment, and in extreme cases, these may even pose a threat to safety at sea. Consequently, strict power quality monitoring of on-board microgrids can also contribute to improving safety while afloat. In this study, a dedicated tool for power quality monitoring is proposed, namely the coeficient of voltage energy efficiency, which has a value proportional to the power losses occurring in induction motors under power quality disturbances.
- Computing Repairs from Active Integrity ConstraintsPublication . Cruz-Filipe, L.; Engrácia, P.; Nunes, I.; Gaspar, G.Repairing an inconsistent knowledge base is a well known problem for which several solutions have been proposed and implemented in the past. In this paper, we start by looking at databases with active integrity constraints - consistency requirements that also indicate how the database should be updated when they are not met - as introduced by Caroprese et al.We show that the different kinds of repairs considered by those authors can be effectively computed by searching for leaves of specific kinds of trees. Although these computations are in general not very efficient (deciding the existence of a repair for a given database with active integrity constraints is NP-complete), on average the algorithms we present make significant reductions on the number of nodes in the search tree. Finally, these algorithms also give an operational characterization of different kinds of repairs that can be used when we extend the concept of active integrity constraints to the more general setting of knowledge bases.