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URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/798

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The Haar wavelets used how expansion function in the method of the moments in the solution of some electrostatic problems
(2010-08-05) Aldo Belardi; CARDOSO, J. R.; SARTORI, C. A. F.
This work presents the methodology from the determination the charge superficial density and electrical fields, in three simple structures to a finite straight wire, square plane plates and the capacitance between to plane plate, all finite and submitted to a constant potential. That involves the method of the moments using as expansion function the Haar wavelets instead of the pulse function, in order to reach a good precision and reducing the computational execution time. We also intend to take advantages of the wavelets application through the Cholesky decomposition, talking about formation of scattered matrixes, and the detection of nulls values.
Thin-film lateral SOI pin diodes for thermal sensing reaching the cryogenic regime
(2010-09-01) Michelly De Souza; RUE, B.; FLANDRE, D.; Marcelo Antonio Pavanello
This paper presents the performance of lateral SOI PIN diodes for temperature sensing in the range of 100 K to 400 K. Experimental results indicate that PIN diodes can be used to implement temperature sensors with high accuracy in cryogenic regime, provided that a suitable temperature range is chosen for calibration. Numerical simulations using Atlas two-dimensional simulator were performed in order to confirm this hypothesis and extend the analysis, verifying the accuracy of the existing model.
Performance of source follower buffers implemented with standard and strained triple-gate nFinFETs
(2010-09-05) Marcelo Antonio Pavanello; MARTINO, J. A.; SIMOEN, E.; ROOYACKERS, R.; COLLAERT, N.; CLAEYS, C.
In this work the application of standard and strained triple-gate FinFETs in unity-gain source-follower configuration is compared. The analysis is performed by evaluating the buffer voltage gain with respect to the fin width and channel length as well as the total harmonic distortion. It is demonstrated that the application of strained material in narrow FinFETs, when the devices are operating in double-gate mode, can be beneficial for the performance of buffers in any channel length. On the other hand, for triple-gate FinFETs or quasi-planar ones the degradation of the output conductance overcomes the transconductance improvements from strained material and the performance of standard buffers is better than of strained ones. Narrow strained buffers also offer better harmonic distortion.
Temperature and silicon film thickness influence on the operation of lateral SOI PIN photodiodes for detection of short wavelengths
(2011-09-05) Michelly De Souza; BULTEEL, O.; FLANDRE, D.; Marcelo Antonio Pavanello
This work presents an analysis of the temperature influence on the performance of a lateral thin-film SOI PIN photodiodes when illuminated by low wavelengths, in the range of blue and ultra-violet (UV). Experimental measurements performed from 100K to 400K showed that the optical responsitivity of SOI PIN photodetectors is affected by temperature change, being reduced at low and moderately high temperatures. Two-dimensional numerical simulations showed the same trends as in the experimental results, and were used both to investigate the physical phenomena responsible for the observed behavior as a function of the temperature as well as to predict the influence of silicon film thickness downscaling on the photodetector performance.
Influence of fin shape and temperature on conventional and strained MuGFETs' analog parameters
(2011-09-05) BUHLER, R. T.; Giacomini R.; MARTINO, J. A.
This work evaluates two important technological variations of Triple-Gate FETs: the use of strained silicon and the occurrence of non-rectangular body cross-section. The anaysis is focused on the electrical parameters for analog applications, and covers a temperature range from 150 K to 400 K. The comparison of the intrinsic voltage gain between the different trapezoidal fin shapes showed that the fin shape can have a major role in some analog parameters than the use of the strained silicon technology, helping to improve those parameters under certain circumstances. The highest intrinsic voltage gains were obtained for strained devices with top fin width larger than bottom at low temperature. Besides the intrinsic voltage gain, were also studied: the threshold voltage, subthreshold swing, drain induced barrier lowering, channel resistance, total harmonic distortion, transconductance, transconductance to drain current ratio, output conductance, Early voltage, drain voltage saturation and unity gain frequency.
QFT control applied to a Drive by Wire (DBW) system
(2012-01-05) Delatore F.; Fabrizio Leonardi; CARVALHO, A. T.; MORIOKA, C. A.
Tradionally, the throttle valve positioning was performed mechanically by means of a steel cable. Nowadays at the embedded system stage, an electromechanical system named as Drive by Wire (DBW) substitutes the direct positioning. The DBW is controlled by the vehicle Engine Control Unit (ECU) and is responsible to adjust the mass air flow delivered to the engine and to control the idle engine rotation. The throttle valve control is somehow a challenging task because of nonlinear phenomena caused by the spring and the gearbox. The present work aims to design a robust parametric control for a DBW system, using a plant model identified numerically at different operations points. The results show that the controller is able to deal with the nonlinear phenomena providing a reasonable performance with no steady state error and a consistent setting time.
Robust model matching control applied to a crane
(2012-01-05) DE CAMPOS, E. L. L.; Fabrizio Leonardi
This paper discusses the robust closed loop control design subject to parametric uncertainties applied to a crane during a maneuver. Usually crane trajectories are generated by formulating a minimum time optimal control in open loop. However, the optimality of the solution is not maintained due to variations in the plant over time. This work proposes the use of a model matching structure to reduce the problems related to model uncertainties thus trying to preserve the trajectory optimality. The robust compensator minimizes explicitly the matching error between the real plant and the reference plant. In this application the main uncertain parameter is the pendulum length and plays the role of the load lifting. To illustrate the application experiments were done using a lab scale equipment. The results observed are very close to those obtained from numerical simulation.
A simple electron mobility model considering the silicon-dielectric interface orientation for circular surrounding-gate transistor
(2012-01-05) PERIN, A. L.; PEREIRA, A. S. N.; AGOPIAN, P. G. D.; Joao Antonio Martino; Giacomini R.
AIn this work, a simple model that accounts for the variation of electron mobility as a function of the silicondielectric interface crystallographic orientation is presented. Simulations were conducted in order to compute the effective mobility of planar devices and its results were compared to experimental data for several interface orientations. The error between experimental data and the proposed model remained bellow 4%. The model has been applied to nMOS circular surrounding gate (thin-pillar transistor - CYNTHIA) and allowed the observationof current density variations as a function of the interface orientation around the silicon pillar.
Fin cross-section shape influence on short channel effects of mugfets
(2012-05-05) BUHLER, R. T.; Giacomini R.; Marcelo Antonio Pavanello; Joao Antonio Martino
Multiple-gate FETs is normally constructed on pre-etched silicon fins. These devices often present casual width variations along the silicon height; mostly caused by technological limitations of the fin definition process, due to non-ideal anisotropic etch. The resulting devices have, consequently, non-rectangular cross-sections, which can affect their electrical behavior. This work addresses the dependence of fin width non-uniformity on the occurrence of short-channel effects through comparative analysis, based on threedimensional numeric simulation of non-rectangular cross-section devices. The influence of the fin crosssection shape on electrical parameters showed to be dependent on channel length, becoming more sensible to the fin shape as the channel length is reduced, with better DC performance present on devices with bottom fin width smaller than top fin width due to the higher transconductance and lower output conductance, resulting on higher intrinsic voltage gain. For opposite fin shapes the total gate capacitance present higher values, beneficiating AC analog parameters, such as unit gain frequency.
Impact of the series resistance in the I-V characteristics of junctionless nanowire transistors and its dependence on the temperature
(2012-01-05) Rodrigo Doria; TREVISOLI, R. D.; Michelly De Souza; Marcelo Antonio Pavanello
The effect of the source/drain parasitic resistance (R S) on the I-V characteristics of Junctionless Nanowire Transistors (JNTs) has been evaluated through experimental and simulated data. The impact of several parameters such as the temperature, the fin width, the total doping concentration, the source/drain length and the source/drain doping concentration on R S has been addressed. The source/drain parasitic resistance presented by JNTs was compared to the one presented by classical inversion mode (IM) triple gate devices, showing opposite behavior with the temperature variation in IM triple transistors and JNTs. In the latter, a reduction on R S is noted with the temperature increase, which is related to the incomplete ionization. This effect inhibits the presence of a Zero Temperature Coefficient (ZTC) operation bias in the Junctionless devices.

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