José Machado da Silva | Universidade do Porto (original) (raw)

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Papers by José Machado da Silva

European Design and Test Conference, Mar 11, 1996

The design, manufacture and operational characteristics (e.g., yield, performance, and reliabilit... more The design, manufacture and operational characteristics (e.g., yield, performance, and reliability) of modern electronic integrated systems exhibit extreme levels of complexity that cannot be easily modelled or predicted. Different mathematical methodologies have been explored to address this issue. Monte Carlo simulation is the most widely employed and straightforward approach to evaluate the circuits' performance statistics. However, the high number of trial cases and the long simulations times required to obtain results for complex circuits with a ppm resolution, lead to very long analysis times. The present work addresses the evaluation of alternative statistical inference methodologies which allow obtaining similar results departing from a smaller dimension data set of Monte Carlo simulations from which the overall population is estimated. These methodologies include the use of Bayesian inference, Expectation-Minimization, and Kolmogorov-Smirnov tests. Results are presented which show the validity of these approaches.

A method for characterizing ¤ ¥ modulators is described which can be built in large integrated ci... more A method for characterizing ¤ ¥ modulators is described which can be built in large integrated circuits or systems-on-chip. The method can be used to measure gain and phase, as well as, total harmonic distortion and signal to noise and harmonic distortion ratio parameters. It is prone to be built in circuit, when computational resources such as digital signal processors or re-programmable logic are available, but can also be used in computer simulations making it easier to compare expected with measured performances.

⎯ An electronic calibration technique for capacitive MEMS accelerometers based on the measurement... more ⎯ An electronic calibration technique for capacitive MEMS accelerometers based on the measurement of pull-in voltages is described. A combination of pull-in voltages and resonance frequency measurements can be used for the estimation of processinduced variations in device dimensions from layout and deviations in material properties from nominal value, which enables auto-calibration. Measurements on fabricated devices confirm the validity of the proposed technique and electronic calibration is experimentally demonstrated.

This paper presents the design and implementation of a GaN-HEMT, c1ass-J power amplifier suitable... more This paper presents the design and implementation of a GaN-HEMT, c1ass-J power amplifier suitable for cognitive radio transceivers, i. e., which presents high-efficiency and wideband characteristics, being these maintained for large load variations. Simulation results are presented which show large signal measurement results of 30 dB gain with 60%-76% power added efficiency (PAE) over a band of 1.3-2.3 GHz. Adaptivity to load changes is being developed to ensure PAE above 70% for large load variations.

2015 Conference on Design of Circuits and Integrated Systems (DCIS), 2015

2014 11th International Conference on Wearable and Implantable Body Sensor Networks Workshops, 2014

Proceedings ED&TC European Design and Test Conference

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One can find today system-on-chip devices comprising also radio-frequency blocks. These highly in... more One can find today system-on-chip devices comprising also radio-frequency blocks. These highly integrated circuits raise extraordinary challenges for testing, jeopardizing the low cost requirements associated often to these products. A built-in self test scheme for RF power amplifiers based on a polynomial fitting approach is proposed here, which takes advantage of the existing local oscillator, up-conversion mixer, and pre-driver, allowing for low area overhead and performance degradation. Simulation and experimental results for gain and linearity (1 dB compression and third order interception points) obtained with a GaAs distributed amplifier are presented which confirm the validity of the method. The BIST scheme proposed for implementing this method on-chip is then described, together with preliminary simulation results.

Computer Standards & Interfaces, 2000

DYNAD, a Standards, Measurements and Testing project supported by the European Commission within ... more DYNAD, a Standards, Measurements and Testing project supported by the European Commission within the Framework IV activities, is a research project aiming at the investigation of test procedures for evaluating the dynamic performances of A/D converters and S/H circuits. The paper concisely reports about the activities carried out in the first months of the project, activities which aim at improving

IEEE transactions on bio-medical engineering, 2015

One of the currently available treatments for aortic aneurysms is endovascular aneurysm repair (E... more One of the currently available treatments for aortic aneurysms is endovascular aneurysm repair (EVAR). In spite of major advances in the operating techniques, complications still occur and lifelong surveillance is recommended. In order to reduce and even eliminate the commonly used surveillance imaging exams, as well as to reduce follow-up costs, new technological solutions are being pursued. In this paper, we describe the development, including design and performance characterization, of a flexible remote pressure measurement system based on inductive-coupling for post-EVAR monitoring purposes. The telemetry system architecture and operation are described and main performance characteristics discussed. The implantable sensor details are provided and its model is presented. Simulations with the reading circuit and the sensor's model were performed and compared with measurements carried out with air and a phantom as media, in order to characterize the telemetry system and validat...

2020 XXXV Conference on Design of Circuits and Integrated Systems (DCIS), 2020

Natural teeth eventually fall out as one becomes older, making it more difficult chewing, speakin... more Natural teeth eventually fall out as one becomes older, making it more difficult chewing, speaking and get a reference plane for the body postural equilibrium. To minimize the problem, the missing teeth are eventually replaced by implants that restore the referred functions but miss the sensing of the applied force. As a consequence, the masticatory forces become erratic as the brain receives no feedback (or inaccurate) sensing information. The present work aims at developing a preliminary prototype of a smart dental implant meant to restore the proprioceptive control of the masticatory and chewing muscle activity. After the description of the physiological and biomechanical aspects related to tooth loss, details are provided on the force sensing and electrical stimulation provided by the active implant being proposed. Simulation results obtained with the development tool of the GreenPAK programmable chip being used are included.

This report is based upon work from COST Action (ENJECT TD1405), supported by COST (European Coop... more This report is based upon work from COST Action (ENJECT TD1405), supported by COST (European Cooperation in Science and Technology).

In-circuit testing methodologies are required to tackle the evaluation of embedded radio-frequenc... more In-circuit testing methodologies are required to tackle the evaluation of embedded radio-frequency circuits. This paper presents design considerations for the test circuitry proposed to implement a methodology for on-chip testing a low-noise amplifier. The scheme being proposed includes an oscillator as the stimulus generator, the redesign of the LNA input switch for test controllability, and an RMS-DC converter to measure the LNA's output power. Simulation results for 1dB compression and third-order intercept points show a good agreement with the expected ones. Index Terms-RF, testability and test techniques, low noise amplifier.

This paper presents preliminary results on the implementation of a wired body area network to be ... more This paper presents preliminary results on the implementation of a wired body area network to be used for human motion capture with the goal of detecting and identifying mobility impairments. Such a wearable system includes sensors embedded in a textile substrate connected to each other with conductive yarns to form a mesh network. The system uses sensor nodes to acquire electromyographic signals and inertial data from accelerometers and gyroscopes. The network employs the SRMCF routing protocol to send the acquired data to a central processing module, from where they are sent via a wireless link to a desktop computer for final processing. The paper describes the first sensor node and central processing module prototypes, the first results on the communication protocol implementation, as well as locomotion data acquired with the system. The SRMCF protocol was implemented using the C language on a 16-bit microcontroller. All acquired data is processed by a Matlab application running ...

Proceedings of IEEE International Symposium on Circuits and Systems - ISCAS '94

Page 1. 161 An Approach to Testability Improvement of Mixed-Signal Boards JosC S. Matos Jog0 C. F... more Page 1. 161 An Approach to Testability Improvement of Mixed-Signal Boards JosC S. Matos Jog0 C. Ferreira Ana C. Le50 Jose M. Silva Dep. of Elect. and Comp. Eng. University of Porto Dep. of Elect. and Comp. Eng. University of Porto INESC Dep. of Elect. and Comp. Eng. ...

A test technique for capacitive MEMS accelerometers and electrostatic micro-actuators based on th... more A test technique for capacitive MEMS accelerometers and electrostatic micro-actuators based on the measurement of pull-in voltages is described. A combination of pull-in voltages and resonance frequency measurements can be used for the estimation of processinduced variations in device dimensions from layout and deviations in material properties from nominal value, which enables auto-calibration. Preliminary measurements on fabricated devices confirm the validity of the proposed technique. Moreover, long-term pull-in measurements have indicated the suitability of the approach as in-system diagnostic tool.