A. Cruz Serra

Automated ADC characterisation using the histogram test stimulated by Gaussian noise

A broadband variant of the histogram test where Gaussian noise is used as a stimulus signal is presented. A methodology allowing for an automated and extensive characterization of analog-to-digital converters (ADCs) is given. Tolerance and confidence intervals are determined both for the integral nonlinearity (INL) and differential nonlinearity (DNL) vectors, related to the number of samples acquired. Experimental results of the characterization of a VXI waveform digitizer using this methodology are shown.

Automatic calibration of analog and digital measuring instruments using computer vision

This paper presents an automatic calibration system capable of calibrating measuring instruments that do not have a digital interface. Image analysis algorithms are used to automatically determine the instrument reading. It can be used with analog and with digital displays. The maximum uncertainty in the detection of the pointers position in analog instruments is less than the human eye can discriminate.

A one‐dimensional, self‐consistent numerical solution of Schrödinger and Poisson equations

A self‐consistent, one‐dimensional, numerical solution of Schrodinger and Poisson equations has been obtained. To solve Schrodinger equation, instead of the conventional finite difference approach, we start by dividing the space in intervals of constant potential energy, in which the solution type is well known. Next we match the wave functions and their first derivatives, divided by the effective mass on each side of the potential steps. This approach is very efficient on finding the eigenvalues in structures with large regions of almost constant potential energy such as quantum well structures or heterojunctions. Validation is presented by comparing the exact solution of Schrodinger equation for a triangular well with that obtained by our method. Poisson equation is solved considering the deep (DX) and shallow centers assuming a donor with one ground state and two excited states. Applications to isotype n‐GaAs/AlxGa1−xAs graded heterojunctions show that the density of the two‐dimensional electron gas (2...

New methods to improve convergence of sine fitting algorithms

One of the recommended test methods in Analog to Digital testing standards is based on least square sine fitting algorithms. The parameter estimation provided by these algorithms is exposed to errors due to different causes. In particular convergence to local minimums of the error function is an open problem. In this paper we present new methods that improve results in sine wave parameter estimation when the frequency is unknown, assuring convergence even in the presence of saturation, noise or distortion. These new methods are also usable in other signal processing applications since they work without loss of quality when only one period of the input signal is acquired.

Computer vision applied to the automatic calibration of measuring instruments

Abstract This paper presents computer vision techniques developed for an automatic calibration system that can automatically determine the reading of the measuring instruments even if they do not have a digital interface that enables the computer to communicate with it. The system is capable of working with instruments that have an analog or a digital display. The error in the determination of the instrument’s reading is less than that introduced by the human eye/brain when the calibration is done manually.

DSP Based Portable Impedance Measurement Instrument Using Sine-Fitting Algorithms

The development and implementation of a digital signal processor (DSP) based portable impedance measurement instrument is described in this paper. The circuit sinewave stimulus is generated by the device using a direct digital synthesizer at the desired measurement frequency. The sine is applied to a reference impedance in series with the unknown impedance. Two analog to digital converters (ADCs) acquire multiple samples of the two sine voltages which are transmitted to the DSP. Sine-fitting algorithms determine the sine amplitudes, phases, DC components and frequency. From these values and the reference impedance values, the impedance amplitude and phase are determined. Included in the device, amplifiers extend the ADCs input range while a digital potentiometer enables the adjustment of the reference impedance to improve accuracy

A new measurement method for the static test of ADCs

Abstract In this paper, a new method for the static test of analog-to-digital converters (ADCs) is proposed. This method uses a variable step size calculated by using an extrapolated convergence factor method. It is shown that it speeds up dramatically the static characterisation procedure and that it could substitute with advantage the traditional static test procedure, especially when a small step size is used. Results obtained by different methods as a function of the step size, of the number of samples and of the relation between the ADC resolution and the expected standard deviation of the noise present in the experimental setup, are shown.

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.

On-line Detection and Classification of Power Quality Disturbances in a Single-phase Power System

A new method for detection and classification of power quality (PQ) disturbances in single-phase power systems is presented in this paper. The method detects transients, waveform distortions and short and long duration disturbances such as sags or swells. The method was developed with special consideration for its suitability for implementation in a digital signal processor (DSP) and for real-time operation. The proposed method was implemented and its performance was verified on detection of real PQ disturbances in a PC based system monitoring a single-phase power system.

Dithering performance of oversampled ADC systems affected by hysteresis

Abstract This paper addresses the problem of hysteresis in ADC systems and the improvement that can be obtained in the performance of such systems with the use of dithering and oversampling. The paper starts with an analysis of ADC hysteresis errors considering their effect on the quantization error and effective number of bits of an ADC system. It concludes with a study of the improvements obtained using dithering in over sampled ADC systems with hysteresis errors. Special attention is paid to the effect of different time sequences of a deterministic dither signal. Experimental results that validate theoretical predictions are also presented.