Gaetano Iuculano

Analog network testability measurement: a symbolic formulation approach

A symbolic formulation approach is applied to the problem of computing testability features of analog linear networks. The program, SAPTES, obtained by following this approach is presented. The program can be a very useful tool for designers and researchers in the field of linear analog circuits. SAPTES, which is written in LISP and runs on MS-DOS personal computers, is able to compute the testability of linear circuits of rather high complexity (composed of tens of components and nodes). Computational times range from a few tens of seconds to some tens of minutes on medium speed computers. The program is easily transportable to workstations or a mainframe, and, for the mainframe, program performance will considerably increase. >

Multifrequency measurement of testability with application to large linear analog systems

With increasing electronic circuit complexity, assessing the testability features becomes a necessity during the design, implementation, and operational or maintenance phases of an analog system. A quantitative measure of testability, based on several multifrequency stimuli, is adopted which is able to handle multiple faults and may provide information also on the degree of complexity encountered in a specific test. An efficient and practical algorithm is proposed which is associated with the result of Sen and Saeks and has a well-defined interpretation even with a large number of circuit parameters liable to failure. The described technique is a basis for optimizing the number and allocation of the selected test points; furthermore, it may serve as an aid in functional partitioning of the same system to facilitate testing and/or reduce computational complexity. An application to a classical active filter is also given.

Improvements to numerical testability evaluation

In this paper, some recent theoretical developments are reviewed and associated algorithms are proposed to determine the numerical testability for large multiinput multioutput systems. In our approach, the modified nodal analysis and the usual techniques for the sensitivity computation in the frequency domain are employed. According to the theoretical basis provided by Sen and Saeks [1] the testability evaluation is related to the computation of the number of linearly independent columns in a convenient form of the sensitivity matrix with rational entries having a common denominator. Then, by extending some results already obtained in [3], it is shown that the above-mentioned number can be determined by computing the numerical rank of a matrix comprised of the coefficients obtained by expanding the numerators of the sensitivities in a suitable orthogonal polynomial series. The numerical rank computation is simplified, particularly for large systems, through an algorithm based on the estimation of the polynomial degrees, which is performed by the iterative comparison between the Chebycheff and the corresponding Stirling coefficients.

Recursive random-sampling strategy for a digital wattmeter

A recursive random-sampling strategy is proposed for the implementation of a digital broadband wattmeter. In this strategy each sampling instant is obtained by adding to the preceding one a predetermined constant lag plus a random increment. In order to correlate the measurement uncertainty to the bandwidth, the asymptotic mean-square error arising from the sampling strategy and the filtering algorithm is evaluated and analyzed; it has been shown that the proposed sampling strategy does not limit the bandwidth of the instrument if an appropriate statistical distribution of the random increments is selected. The theoretical results are compared with those obtained by simulating the measurement process. >

Non-linear dynamic system modelling based on modified Volterra series approaches

Abstract The empirical “black-box” characterization of non-linear systems with memory is a complex problem which cannot be dealt with by means of a unique, general-purpose mathematical approach such as the Volterra series. In fact, from a metrological point of view, the feasibility and reliability of the measurement procedure must be the criterion on the basis of which any mathematical approach for modelling purposes must be evaluated. This paper describes different solutions for the behavioural identification of non-linear dynamic systems, all based on a modified Volterra series, which are characterized by a reduced number of operators with respect to the classical Volterra approach. The operator reduction, which does not affect the accuracy of the obtained models if a mild assumption on the system memory time duration is satisfied, allows a reliable extraction of the model parameters by means of conventional instrumentation, without the need for the generation of complicated input probing signals or additional approximations. A detailed discussion is provided in order to estimate when each of the proposed approaches can be practically used, by pointing out the hypotheses that must be taken into account in order to minimise the modified series truncation errors. Experimental examples, showing the validity of the proposed approaches, are given in the last section of the paper, as well as a comparison between the performances of the different solutions when applied to the important field of electron device characterization.

A modified Volterra series approach for the characterization of non-linear dynamic systems

The paper presents a theoretical study on the convergence properties of the new modified Volterra-like modeling approach for non-linear dynamic systems in comparison with the classical Volterra series representation. In particular, the assumptions which enable a single-fold non-linear convolution integral to be adopted also in the presence of strong non-linearities are pointed out. Experimental and simulation results which confirm the theoretical considerations are also provided.

A broad-band harmonic vector voltmeter based on a random sampling strategy

This paper presents a digital harmonic vector voltmeter based on a random asynchronous sampling strategy. The measurement procedure is described and the problem of estimating both the error due to the time discretization and to the estimation of the periodic complex exponential associated with the input reference signal is discussed.<<ETX>>

Automatic-test equipment for the characterization of aluminum electrolytic capacitors

This paper describes the most important factors influencing the aluminum electrolyte capacitor showing, in particular, the effect of temperature on the lifetime of this device. The automation of the measurement system, with the oven interfaced with a PC, was also completed to control all the involved parameters.

The evaluation of the combined standard uncertainty for nonlinear models

In this work, the law of propagation of uncertainty is studied for complex system with nonlinear properties. Sensitivity analysis is carried out using the Taylors series expansion of higher-order terms than the usual one presented in the ISO (GUM). An experimental problem is considered to verify the obtained theoretical results and to asses the validity of the implemented formulation.

New performance function for the comparison of different sampling strategies in non-linear conversion instruments

A method for the performance evaluation of digital measurement instruments based on asynchronous sampling and nonlinear signal conversion is proposed. The authors propose a performance index for the comparison of different asynchronous strategies and develop the analytical form of that index for two sampling techniques, equally spaced and random. The idea is to interpret the instantaneous output of the instrument as a discrete random variable with a uniform distribution over the successive occasions of measurement. Thus, the asymptotic variance of the reading can be a sum of contributions, each of which is obtained by weighting the contributions relative to each spectral component of the signal according to a frequency-dependent coefficient which is assumed to the performance index.<<ETX>>