Francisco Alegria

Performance analysis of an ADC histogram test using small triangular waves

The histogram method using small-amplitude triangular waves for the quasi-static test of analog-to-digital converters has been proposed for standardization aims. In this paper, after a brief description of the test procedure, analytical closed-form relations for designing the test, as well as for its characterization in terms of efficiency and uncertainty, are provided. Numerical and experimental results of a comparative analysis with the IEEE 1057-standard static test highlight its better performance in terms of efficiency and accuracy.

An ADC histogram test based on small-amplitude waves

Abstract This paper deals with a new method improving the static test for analogue-to-digital converters. The method is based on a histogram procedure using as test signals small-amplitude triangular waves superimposed on suitable constant offset values. The histogram is built over the converter fullscale by varying the offset step by step systematically. A small amplitude and a reduced time slope in comparison to the converter range and slew rate, respectively, lead to static test conditions. This procedure allows inexpensive function generators to be used and the test duration to be dramatically reduced. Experimental results of tests aimed at validating, characterizing, and comparing the proposed method on two different converter architectures are presented.

Liftoff Correction Based on the Spatial Spectral Behavior of Eddy-Current Images

In this paper, a new processing scheme for compensating the liftoff effect is proposed to increase the signal-to-noise ratio of measurements carried out when a duralumin plate with artificially manufactured defects was scanned with eddy-current probes. The mathematical algorithm is based on the spatial frequency behavior of the output signals with the liftoff distance (the distance between the probe used for inspection and the sample) and its equivalent form (deconvolution) in the spatial domain. Results are presented for measurements performed at three different distances for the same defect of the duralumin plate.

ADC histogram test by triangular small-waves

A histogram-based method for quasi-static test of analog-to-digital converters has been proposed for standardization aims. The test exploits the use of small-amplitude triangular waves. Different signal offset values are used to fully stimulate the converter input range. The reduced amplitude and slope of the input triangular wave with respect to the converter range and slew rate, respectively, lead to quasi-static test conditions. The test allows (i) linearity constraints of function generators to be relaxed, and (ii) experimental burdens to be reduced. In this paper, after a brief recalling of the test procedure, analytical relations for designing an efficient test are provided. Numerical and experimental results of a comparative analysis with the IEEE 1057-standard static test highlight its better performance.

Standard Histogram Test Precision of ADC Gain and Offset Error Estimation

The quality of measurements made in any system is quantified by supplying the expanded uncertainty of the result, as recommended in the Guide to Uncertainty in Measurement. In a system that involves analog-to-digital converters (ADCs), one of the sources of uncertainty is the converters gain and offset error. The uncertainty of these two parameters should be known in order to compute the uncertainty of the measurements made with the system. In this paper, we study the uncertainty of terminal-based defined gain and offset error that are estimated using a standard histogram test in the presence of an additive noise.

IEEE 1057 Jitter Test of Waveform Recorders

The jitter test of waveform recorders and analog-to-digital converters (ADCs) is traditionally carried out using one of the methods recommended in the IEEE standard for digitizing waveform recorders, i.e., IEEE Standard 1057. Here, we study the uncertainty of one of those methods, point out the bias inherent to the estimator recommended for measuring the ADC jitter, and suggest an alternate estimator. Expressions are also presented for the determination of the precision of a given estimate from the number of samples used, the standard deviation of the additive noise present in the test setup, the jitter standard deviation, and the stimulus signal parameters. In addition, an expression for the computation of the minimum number of samples required to guarantee a given bound on the estimation uncertainty is presented, which is useful in optimizing the duration of the test.

Fast ADC Testing by Repetitive Histogram Analysis

Modeling the integral nonlinearity by the unified behavioral error model which is expressed as one dimensional image in the code k domain requires a minimal number of error parameters. The unified error model consists of low and high code frequency components. The paper presents new methods for low code frequency and high code frequency testing. The identification of low code and high code frequency components is based on a stochastic analysis of both components by using harmonic signals with reduced amplitude. The high code frequency component for code bins with extraordinary high nonlinearities is estimated in the statistical domain by a narrow band histogram using sinusoidal stimulus. The uncertainty of the proposed method is being assessed in the paper for various ADC representatives

Effective ADC linearity testing using sinewaves

This paper deals with the effectiveness of the sinewave histogram test (SHT) for testing analog-to-digital converters. The implementation is discussed, with respect to the adopted procedures and to the choice of relevant parameters. Some of the published approximations currently limiting the characterization of the test performance are removed. The statistical efficiency of the SHT is evaluated by comparing the associated estimator variance with the corresponding Crame/spl acute/r-Rao lower bound, theoretically derived assuming sinewaves corrupted by Gaussian noise. Finally, both simulation and experimental results are presented to validate the proposed approach.

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.

Design and test of a high-resolution acquisition system for marine seismology

Active and passive seismology require high-resolution, low-level signal acquisition. In both methods, the equipment most widely used to acquire seismic data in the marine environment is an ocean bottom seismometer (OBS). We designed and built a high-resolution acquisition system prototype for an OBS that is mainly used in active seismic experiments in which maps are generated of the width and material of ocean bottom sublayers. Other OBS system applications, in which the objective is to estimate the location and magnitude of an earthquake require higher autonomy. When an OBS is used in a permanent seafl oor observatory with no power supply limitation, it can generate tsunami alert signals to shore.