DEE_ARIAC http://hdl.handle.net/10362/1734 2013-05-19T19:05:48Z 2013-05-19T19:05:48Z Goes, J. Paulino, N. Galhardo, A. http://hdl.handle.net/10362/4037 2010-08-06T11:26:42Z 2008-04-01T00:00:00Z

Title: Low-power 6-bit 1-GS/s two-channel pipeline ADC with open-loop amplification using amplifiers with local-feedback Authors: Goes, J.; Paulino, N.; Galhardo, A. Abstract: A low-power 1.2 V 6-bit 1-GS/s time-interleaved pipeline ADC designed in 130 nm CMOS is described. It is based on a new 2-channel 1.5-bit MDAC that performs openloop residue amplification using a shared amplifier employing local-feedback. Time mismatches between channels are highly attenuated, simply by using two passive front-end Sample-and-Hold circuits, with dedicated switch-linearization control circuits, driven by a single clock phase. Simulated results of the ADC achieve 5.35-bit ENOB, with 20 mW and without requiring any gain control/calibration scheme. Description: IEEE International Symposium on Circuits and Systems, pp. 2258 – 2261, Seattle, EUA

2008-04-01T00:00:00Z Ortigueira, M.D. Batista, A. G. http://hdl.handle.net/10362/2618 2010-12-03T09:43:16Z 2004-12-01T00:00:00Z

Title: A fractional linear system view of the fractional brownian motion Authors: Ortigueira, M.D.; Batista, A. G. Abstract: A definition of the fractional Brownian motion based on the fractional differintegrator characteristics is proposed and studied. It is shown that the model enjoys the usually required properties. A discrete-time version based in the backward difference and in the bilinear transformation is considered. Some results are presented. Description: Nonlinear Dynamics, Vol. 38

2004-12-01T00:00:00Z Ortigueira, M.D. http://hdl.handle.net/10362/2617 2010-02-08T13:30:52Z 2001-01-01T00:00:00Z

Title: The comb signal and its Fourier transform Authors: Ortigueira, M.D. Abstract: In this paper, we study the aperiodic comb signalfrom the point of view of the Fourier transform. The comb is very important in the theory of ideal sampling. The knowledge of its properties is crucial for the establishment of suitable interpolation schemes. Here, we present sufficient conditions so that the Fourier transform of an aperiodic comb is an aperiodic comb. We use this result to propose: (1) an alternative approach to the de"nition of an almost periodic signal and its anharmonic Fourier series; (2) a generalisation of the Shannon}Whittakker sampling/reconstruction for the irregular sampling case. Application of this theory to pulse duration modulation and pulse position modulation is also presented. Description: SignalProcessing, Vol. 81, nº 3

2001-01-01T00:00:00Z Ortigueira, M.D. Gerald, José A. B. Inácio, José A. L. http://hdl.handle.net/10362/2616 2010-02-08T13:30:48Z 2000-12-01T00:00:00Z

Title: Communicación sobre lineas de suministro de energia Authors: Ortigueira, M.D.; Gerald, José A. B.; Inácio, José A. L. Abstract: Proponemos un sistema para la comunicación sobre líneas de la energia eléctrica usando DS/BPSK con un régimen binario de 300 bits/s. La señal de ensanchado tiene una secuencia máxima de longitud 7 como código de “chip”, repetida 30 veces para cada dígito binario del código de la información BPSK. La sincronización entre la señal del receptor y la secuéncia PN localmente generada es obtenida por un nuevo acercamiento basado en un filtro adaptado. Description: Informacion Tcnológica, vol. 11, nº6

2000-12-01T00:00:00Z