ENIDH – EEM - Artigo Científico
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- FUZYE: A Fuzzy C-Means Analog IC Yield Optimization using Evolutionary-based AlgorithmsPublication . Canelas, António; Póvoa, Ricardo; Martins, Ricardo; Lourenço, Nuno; Guilherme, Jorge; Carvalho, João Paulo; Horta, NunoThis paper presents fuzzy c-means-based yield estimation (FUZYE), a methodology that reduces the time impact caused by Monte Carlo (MC) simulations in the context of analog integrated circuits (ICs) yield estimation, enabling it for yield optimization with population-based algorithms, e.g., the genetic algorithm (GA). MC analysis is the most general and reliable technique for yield estimation, yet the considerable amount of time it requires has discouraged its adoption in population-based optimization tools. The proposed methodology reduces the total number of MC simulations that are required, since, at each GA generation, the population is clustered using a fuzzy c-means (FCMs) technique, and, only the representative individual (RI) from each cluster is subject to MC simulations. This paper shows that the yield for the rest of the population can be estimated based on the membership degree of FCM and RIs yield values alone. This new method was applied on two real circuit-sizing optimization problems and the obtained results were compared to the exhaustive approach, where all individuals of the population are subject to MC analysis. The FCM approach presents a reduction of 89% in the total number of MC simulations, when compared to the exhaustive MC analysis over the full population. Moreover, a k-means-based clustering algorithm was also tested and compared with the proposed FUZYE, with the latest showing an improvement up to 13% in yield estimation accuracy
- A new family of CMOS inverter based OTAs for Biomedical and Healthcare ApplicationsPublication . Póvoa, Ricardo; Canelas, António; Martins, Ricardo; Lourenço, Nuno; Horta, Nuno; Goes, JoãoThis paper presents a new family of innovative operational transconductance amplifier (OTA) topologies based on CMOS inverter structures, with improved gain and energy-efficiency. This new family of OTA designs is suitable for biomedical and healthcare circuits and systems, due to the high energy-efficiency, improved gain and low level of noise contribution, when compared to the state-of-the-art in this field. In this paper, two fully-differential implementations are presented, a first one with a double CMOS branch biased by two pairs of voltage-combiners structures in both NMOS and PMOS configurations, and a second one with folded voltage-combiners specifically targeting low voltage applications, e.g., supplies below 1 V. The usage of voltage-combiners to bias the OTAs improves the gain and the gain-bandwidth product, therefore improving the energy-efficiency figure-of-merit. High values of figure-of-merit are achieved in both implementations, i.e., more than 1600 MHz × pF/mA and 2000 MHz × pF/mA, gain values above 53 dB and 50 dB under supply sources of 2 V and 0.7 V respectively. The folded voltage-combiners biased OTA is able to operate correctly under a voltage supply down to 0.7 V with proper DC biasing. The results are finally compared with state-of-the-art in this field and the potential of the circuits is fulfilled using a state-of-the-art layout-aware integrated-circuit optimization framework, AIDA, particularly relevant in order to overcome the device stacking problematic for lower voltages.
- 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.
- 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.
- A Folded Voltage-Combiners Biased Amplifier for Low Voltage and High Energy-Efficiency ApplicationsPublication . Póvoa, R.; Lourenço, N.; Martins, R.; Canelas, A.; Horta, N.; Goes, J.The topic of this brief is a ingle-stage amplifier biased by a doublet of voltage-combiners in a folded configuration, in order to be supplied by a power source of 1.2 V, maintaining proper dc biasing and avoiding the need of any device stacking. The topology has been automatically designed, optimized, and laid out, from sizing to layout level, using a layout-aware approach provided by the AIDA framework, a state-of-the-art analog IC design optimization framework. Experimental results prove that a gain of approximately 44 dB, together with a figure-of-merit higher than 1300 MHz × pF/mW are achievable using the proposed topology, with standard UMC 130 nm technology devices and a 1.2-V supply source. Finally, an extension to supply sources below nominal is explored, showing exciting results toward a future of high energy-efficiency amplifiers.
- Sub- μW Tow-Thomas Based Biquad Filter with Improved Gain for Biomedical ApplicationsPublication . Póvoa, R.; Arya, R.; Canelas, A.; Passos, F.; Martins, R.; Lourenço, N.; Horta, N.This paper presents an innovative topology of a gm-C Operational Transconductance Amplifier (OTA), with improved gain and energy-efficiency and its corresponding implementation inside a second order Tow-Thomas based filter configuration, for biomedical and healthcare applications. The proposed OTA architecture takes advantage of a current division technique, as well as the usage of a pair of cross-coupled voltage-combiners in replacement of the static current source that traditionally bias the differential pair. The circuitry proposed in this paper is described at analytical level, fully-designed at sizing level and validated at simulation level compounded by Monte Carlo results, using a standard 130 nm technology node. Both the OTA and the biquad filter architecture are compared, in terms of performance indexes, with state-of-the-art bibliography, where the potential of both is demonstrated. The designed filter operates at weak inversion and sub-threshold, being supplied by a 0.9 V source, achieving a cut-off frequency of 15 Hz, a gain of 7 dB, hence improving the input-referred noise and consuming nearly 0.55 μW.
- Uncertainty relations for a non-canonical phase-space noncommutative álgebraPublication . C. Dias, Nuno; N. Prata, JoãoWe consider a non-canonical phase-space deformation of the Heisenberg– Weyl algebra that was recently introduced in the context of quantum cosmology. We prove the existence of minimal uncertainties for all pairs of non-commuting variables. We also show that the states which minimize each uncertainty inequality are ground states of certain positive operators. The algebra is shown to be stable and to violate the usual Heisenberg–Pauli–Weyl inequality for position and momentum. The techniques used are potentially interesting in the context of time-frequency analysis
- A refinement of the RobertsonSchrodinger uncertainty principle and a Hirschman-Shannon inequality for Wigner distributionsPublication . C.Dias, Nuno.; de Grosson, M.; N.Prata, João.We propose a refinement of the Robertson–Schrödinger uncertainty principle (RSUP) using Wigner distributions. This new principle is stronger than the RSUP. In particular, and unlike the RSUP, which can be saturated by many phase space functions, the refined RSUP can be saturated by pure Gaussian Wigner functions only. Moreover, the new principle is technically as simple as the standard RSUP. In addition, it makes a direct connection with modern harmonic analysis, since it involves the Wigner transform and its symplectic Fourier transform, which is the radar ambiguity function. As a by-product of the refined RSUP, we derive inequalities involving the entropy and the covariance matrix of Wigner distributions. These inequalities refine the Shanon and the Hirschman inequalities for the Wigner distribution of a mixed quantum state . We prove sharp estimates which critically depend on the purity of and which are saturated in the Gaussian case.
- Non-rigid registration of 3D ultrasound for neurosurgery using automatic feature detection and matchingPublication . Machado, I.; ToewsJie, M.; Unadkat, L.; Essayed, W.; George, E.; Teodoro, Pedro; Carvalho, H.; Martins, J.; Golland, P.; Pieper, S.; Frisken, S.; Golby, A.; WellsIII, W.
- Ordinary differential equations with point interactions: An inverse problemaPublication . C.Dias, Nuno; Jorge, C.; N.Prata, João.