R. Martins

Simulation and experimental results of multiharmonic least-squares fitting algorithms applied to periodic signals

A new generation of multipurpose measurement equipment is transforming the role of computers in instrumentation. The new features involve mixed devices, such as analog-to-digital and digital-to-analog converters and digital signal processing techniques, that are able to substitute typical discrete instruments like multimeters and analyzers. Signal-processing applications frequently use least-squares (LS) sine-fitting algorithms. Periodic signals may be interpreted as a sum of sine waves with multiple frequencies: the Fourier series. This paper describes an algorithm that is able to fit a multiharmonic acquired signal, determining the amplitude and phase of all harmonics. Simulation and experimental results are presented.

Combined spectral and histogram analysis for fast ADC testing

The integral nonlinearity (INL) of analog-to-digital converters (ADCs) can be described by a behavioral error model expressed as one-dimensional image in the code domain. This image consists of low and high code frequency components which allow describing the ADC performance with a small number of parameters. This paper presents new methods for low code frequency and high code frequency testing. The identification of the low code frequency components is performed by multiharmonic sine fitting in the time domain. The high code frequency components are estimated in the statistical domain by a narrow band histogram test using a triangular stimulus signal. The performance of the proposed method is assessed for various ADC devices.

Analog-to-digital converter testing—new proposals

Abstract New static and dynamic analog-to-digital converter (ADC) testing techniques are revised and discussed. A new test method based on the Histogram Method but using small-amplitude triangular waves with a variable offset is shown to have several advantages over the traditional static test, namely a dramatic reduction in test duration even for high-resolution ADCs. The use of Gaussian noise to stimulate ADCs led to a new dynamic test method that allows the test of high frequency, or high resolution ADCs in those cases where the traditional sinusoidal stimuli are not available with the required spectral purity. The requirements for this test gave birth to a new method of assessing the amplitude distribution and density in stimulus signals, determining the nonlinearities and compensating them. The four-parameter sine fitting algorithm traditionally used in time domain tests is modified in order to improve convergence.

Least-squares fitting algorithms applied to periodic signals

A new generation of multipurpose measurement equipment is transforming the role of computers in instrumentation. The new features involve mixed devices, as analog-to-digital and digital-to-analog converters, and digital signal processing techniques, able to substitute typical discrete instruments like multimeters, analyzers, etc. Signal-processing applications frequently use least-squares sine-fitting algorithms. Periodic signals may be interpreted as a sum of sine waves with multiple frequencies, the Fourier series. This paper proposes a new algorithm which is able to fit a multi-harmonic acquired signal determining the amplitude and phase of all harmonics. Simulation and experimental results are presented.

A case study of two and three-dimensional inversion of dipole-dipole data: the Enfermarias Zn-Pb (Ag, Sb, Au) Prospect (Moura, Portugal)

The Enfermarias Zn-Pb(Ag, Sb, Au) prospect, located in the Moura-Ficalho region (Alentejo, Portugal), was intensively explored during 1980s. A drilling programme was successful, intersecting massive and disseminated sulphide mineralizations. The geological and geophysical data set available for Enfermarias is quite vast and comprises 13 borehole geological logs, as well as gravity, magnetic and resistivity data. In this paper, the dipole-dipole resistivity surveys are re-examined and interpreted using both 2D and 3D inversion to provide an interesting comparison of the two different approaches. Results from gravity data modelling and data from borehole logs are used as independent validity tests on the quality of the results. The 2D and 3D models indicate a conductive overburden covering more resistive bedrock, which appears at a depth of 70–100 m in the western part of the profiles. Results obtained from 3D inversion, however, show a very clear separation of the most resistive domains in the two different bodies, whereas this separation does not appear in the 2D models. The 3D model also shows a higher degree of spatial continuity than the partial 2D models, which are, in general, richer in shortwavelength anomalies, and show a higher variation from profile to profile. Comparison of the resistivity results with gravity in two coincident profiles reveals an excellent agreement between the main shallow features of both 2D and 3D models. This suggests that the resistivity model does indeed satisfy the main features of the available geological and geophysical data.

LA INCLUSIÓN COMO FACTOR DE ÉXITO EN EL PROCESO EDUCATIVO DE NIÑOS CON NECESIDADES EDUCATIVAS ESPECIALES: PERCEPCIONES Y ACTITUDES DEL PROFESOR DE 1er CICLO DE EDUCACIÓN BÁSICA

A necessidade, cada vez mais pertinente de uma escola inclusiva, trouxe mudancas nos ambientes de aprendizagem e no papel dos professores. Com este estudo quisemos conhecer as percecoes e atitudes dos professores do 1.o ciclo do ensino basico em relacao a inclusao dos alunos. As respostas destes foram obtidas atraves de um inquerito por questionario, onde foram inquiridos 56 professores do 1.o ciclo do ensino basico, com afirmacoes sobre os aspetos gerais de Inclusao que se prendem com o seu conceito de beneficios, a capacidade dos professores em responderem as necessidades dos alunos com necessidades educativas especiais e com recursos, tempo e conhecimentos (formacao) necessarios para a implementacao de praticas inclusivas. Atraves dos resultados percebeu-se necessidade de formacao, no seu global sao a favor de uma escola inclusiva, de direito a igualdade e aprendizagem, conscientes de que as suas praticas podem influenciar o desempenho e sucesso das criancas com necessidades educativas especiais.