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Publications

Publications by Manuel Cândido Santos

2014

Transparent Current Mirrors Using a-GIZO TFTs: Simulation with RBF Models and Fabrication

Authors
Bahubalindruni, P; Tavares, V; Duarte, C; Cardoso, N; Oliveira, P; Frias, R; Barquinha, P; Martins, R; Fortunato, E;

Publication
2014 UKSIM-AMSS 16TH INTERNATIONAL CONFERENCE ON COMPUTER MODELLING AND SIMULATION (UKSIM)

Abstract
This paper analyzes transparent two-TFT current mirrors using a-GIZO TFTs with different mirroring ratios. In order to achieve a high mirroring ratio, the output TFT in the circuit employed a fingered structure layout to minimize area and overlap capacitance. The analysis of the current mirrors is performed in three phases. In the first, a radial basis function based (RBF) model is developed using measured data from fabricated TFTs on the same chip. Then, in the second phase, the RBF model is implemented in Verilog-A that is used to simulate two-TFT current mirrors with different mirroring ratios. The simulations are carried out using Cadence spectre simulator. In the third phase, simulation results are validated with the measured response from the fabricated circuits.

2013

Transparent Current Mirrors With a-GIZO TFTs: Neural Modeling, Simulation and Fabrication

Authors
Bahubalindruni, PG; Tavares, VG; Barquinha, P; Duarte, C; de Oliveira, PG; Martins, R; Fortunato, E;

Publication
JOURNAL OF DISPLAY TECHNOLOGY

Abstract
This paper characterizes transparent current mirrors with n-type amorphous gallium-indium-zinc-oxide (a-GIZO) thin-film transistors (TFTs). Two-TFT current mirrors with different mirroring ratios and a cascode topology are considered. A neural model is developed based on the measured data of the TFTs and is implemented in Verilog-A; then it is used to simulate the circuits with Cadence Virtuoso Spectre simulator. The simulation outcomes are validated with the fabricated circuit response. These results show that the neural network can model TFT accurately, as well as the current mirroring ability of the TFTs.

2017

System Design for Wireless Powering of AUVs

Authors
Ressurreicao, T; Goncalves, F; Duarte, C; Goncalves, R; Gomes, R; Santos, R; Esteves, R; Pinto, P; Oliveira, I; Pessoa, LM;

Publication
OCEANS 2017 - ABERDEEN

Abstract
The present work addresses the design of an electronic system for powering autonomous underwater vehicles (AUVs). We report the study and implementation of a system developed for transmitting and receiving wireless power in water from a docking station to an AUV. A simplified analysis is presented regarding the operation of a class-D power driver in a series-series inductive resonant coupling topology. We further investigate the compromise between link efficiency and power delivery of the system to circumvent the reduced power output capability. Simulation results are provided as well as measurement data validated using circuit prototypes in an experimental setup with a structure similar to the docking station of the AUV filled with salt water.

2016

Yield Prediction With a New Generalized Process Capability Index Applicable to Non-Normal Data

Authors
Weber, S; Ressurreicao, T; Duarte, C;

Publication
IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS

Abstract
Monte Carlo (MC) techniques are widely applied to check a design on its robustness and for estimating the production yield of integrated circuits. Using standard random MC and the sample yield for estimation, a very large number of samples is required for accurate verification, especially if a high yield is desired. This can make MC extremely time consuming, but if the data follows a normal Gaussian distribution a much faster yield prediction is possible by using the well-known C-PK method. We extended this specification-distance-based scheme for the far more difficult general non-normal case by three different means, ending up in a new generalized process capability index named C-GPK. First, we apply parametric modeling only to the specification-sided distribution part. This way any difficulties in distribution parts that actually have little yield impact do not degrade the model fit anymore. Second, to improve the parametric model we introduce a new tail parameter t. Third, to allow modeling of difficult asymmetrical, multimodal or flat distributions we also introduce a new reference location parameter instead of using the mean. An advantage of improving MC this way is that-in opposite to many other MC enhancements (like importance sampling)-the performance of the C-GPK is not negatively impacted by design complexity. We described the formulation of the C-GPK and derived confidence intervals using an advanced bootstrap scheme. We verified the performance against the sample yield and C-PK for a representative set of distributions, including real production data and MC data from the design of a CMOS operational amplifier and other circuits.

2017

Performance improvement of a buck converter using Kalman filtering

Authors
Gora, W; Duarte, C; Costa, P; Pereira, A;

Publication
International Journal of Power Electronics

Abstract

2014

Environment-Aware System for Alzheimer's Patients

Authors
Barreto, A; Oliveira, R; Sousa, F; Cardoso, A; Duarte, C;

Publication
2014 EAI 4TH INTERNATIONAL CONFERENCE ON WIRELESS MOBILE COMMUNICATION AND HEALTHCARE (MOBIHEALTH)

Abstract
Alzheimer's disease is a major cause of disability in older people and because of its nature and symptoms it is a huge weight on the caregivers and health system. The aim of this project, developed at Fraunhofer Portugal, is to create a remote monitoring system for patients suffering from Alzheimer's disease. This system comprises a device able to monitor the environment temperature and humidity, the patients location, using GPS, as well as the patient's movements, including falls. The device sends this information to the caregiver via SMS, and also to a server, where it is stored in a database developed in this work, and which the caregiver can access via a smartphone, using an application also developed in this project. This system therefore affords a close surveillance of the patient's status as well as access to historical data of the patient's information.

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