ENIDH – EEM - Artigo Científico
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- 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.
- 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.
- Single Stage OTA biased by Voltage-Combiners with Enhanced Performance using Current StarvingPublication . Póvoa, R.; Lourenço, N.; Martins, R.; Canelas, A.; Horta, N.; Goes, J.This brief presents an improved single-stage amplifier biased by voltage-combiners, through the proper usage of current starving. The topology designed and fabricated shows an enhancement of the low-frequency gain, an improvement in the establishing time due to enhanced gain-bandwidth product, and a high improvement of the energy efficiency. The circuit was optimized using AIDA-C, a state-of-the-art multi-objective multi-constraint analog IC sizing and optimization tool, and simulation results demonstrate that a gain above 60 dB and a figure-of-merit over 900 MHz×pF/mA are acquirable with this circuit, using the UMC 130-nm technology design kit. The circuit was fabricated and experimentally measured, presenting a gain of 58 dB with a figure-of-merit of 1102 MHz×pF/mA, for a 3.3 V supply source.
- Single-Stage Amplifier biased by Voltage-Combiners with Gain and Energy-Efficiency EnhancementPublication . Póvoa, R.; Lourenço, N.; Martins, R.; Canelas, A.; Horta, N.; Goes, J.This brief presents the design of a single-stage amplifier with enhanced gain and speed, without the need for using any cascode devices, positive feedback, or feed forward technique. Instead, two voltage-combiners replace the traditional tail current source, commonly employed to bias the differential pair. The resultant topology shows both additional dc gain and a gain bandwidth product enhancement. Simulation results of a properly optimized circuit, using AIDA-C, a state-of-the-art multi-objective multi-constraint IC sizing and optimization tool, demonstrate that a dc gain above 47 dB and a figure-of-merit better than 960 MHz*pF/mA, in corner conditions, can be achieved with this topology, in the UMC 130-nm technology. The circuit was fabricated and experimentally measured, showing an energy-efficiency figure-of-merit of 1023.6 MHz*pF/mA.
- Fractional Order Image Processing of Medical ImagesPublication . Bento, Tiago; Valério, Duarte; Teodoro, Pedro; Martins, JorgeTo perform a robot-assisted surgery of a prosthesis implantation on a patient’s femur, we may need to get the femoral head-neck orientation for the application. We can extract that information from Computed Tomography scans, using image processing. In image processing, edge detection often makes use of integer-order differentiation operators (e.g. Canny and LoG operators). This paper shows that introducing non-integer (fractional) differentiation to edge detectors (Fractional Canny, Fractional LoG, Fractional Derivative operators) can improve automatic edge detection results.
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