Regression modeling for digital test of ΣΔ modulators

The cost of Analogue and Mixed-Signal circuit testing is an important bottleneck in the industry, due to timeconsuming verification of specifications that require state-ofthe- art Automatic Test Equipment. In this paper, we apply the concept of Alternate Test to achieve digital testing of converters. By training an ensemble of regression models that maps simple digital defect-oriented signatures onto Signal to Noise and Distortion Ratio (SNDR), an average error of 1:7% is achieved. Beyond the inference of functional metrics, we show that the approach can provide interesting diagnosis information.Ministerio de Educación y Ciencia TEC2007-68072/MICJunta de Andalucía TIC 5386, CT 30

Programmable low-voltage continuous-time filter for audio applications

The implementation of a continuous-time filter (CTF) useful for audio frequency applications is presented in this paper. The filter functions can be programmed and tuned with two independent control variables. The filter here proposed has been designed to work at 1.5 V of power supply and at a maximum of 0.5 /spl mu/A/OTA for the worst case current consumption. Electrical simulations of a Tow-Thomas biquad (TTB) show the possibility of obtaining low-pass and band-pass filter functions over the 10 Hz-40 kHz frequency range by changing a control current over four decades.Comisión Interministerial de Ciencia y Tecnología TIC-97-064

Design of a CMOS closed-loop system with applications to bio-impedance measurements

This paper proposes a method for impedance measurements based on a closed-loop implementation of CMOS circuits. The proposed system has been conceived for alternate current excited systems, performing simultaneously driving and measuring functions, thanks to feedback. The system delivers magnitude and phase signals independently, which can be optimized separately, and can be applied to any kind of load (resistive and capacitive). Design specifications for CMOS circuit blocks and trade-offs for system accuracy and loop stability have been derived. Electrical simulation results obtained for several loads agree with the theory, enabling the proposed method to any impedance measurement problem, in special, to bio-setups including electrodes.Ministerio de Ciencia e Innovación TEC2007-6807

Doppler tomography of Cataclysmic Variables

The study of cataclysmic variables (CVs), and in particular of the evolution of their accretion discs throughout their different brightness states, has benefited largely from the use of indirect imaging techniques. I report on the latest results obtained from Doppler tomography of CVs concentrating mainly on results published since the 2000 Astrotomography meeting in Brussels. Emphasis is given to the spiral structures found in the accretion discs of some CVs, to the evolution of these structures throughout quiescence and outburst, and to our search for them in more systems.Comment: 4 pages, 1 figure. Accepted for publication in AN. Proceedings of the Astrotomography Joint Discussion 09 of the IAU General Assembly 2003. Uses an.cl

On Essential Incompleteness of Hertz's Experiments on Propagation of Electromagnetic Interactions

The historical background of the 19th century electromagnetic theory is revisited from the standpoint of the opposition between alternative approaches in respect to the problem of interactions. The 19th century electrodynamics became the battle-field of a paramount importance to test existing conceptions of interactions. Hertz's experiments were designed to bring a solid experimental evidence in favor of one of them. The modern scientific method applied to analyze Hertz's experimental approach as well as the analysis of his laboratory notes, dairy and private letters show that Hertz's "\textit{crucial}" experiments cannot be considered as conclusive at many points as it is generally implied. We found that alternative Helmholtz's electrodynamics did not contradict any of Hertz's experimental observations of transverse components as Maxwell's theory predicted. Moreover, as we now know from recently published Hertz's dairy and private notes, his first experimental results indicated clearly on infinite rate of propagation. Nevertheless, Hertz's experiments provided no further explicit information on non-local longitudinal components which were such an essential feature of Helmholtz's theory. Necessary and sufficient conditions for a decisive choice on the adequate account of electromagnetic interactions are discussed from the position of modern scientific method

A perturbed differential resultant based implicitization algorithm for linear DPPEs

Let \bbK be an ordinary differential field with derivation $\partial$. Let \cP be a system of $n$ linear differential polynomial parametric equations in $n-1$ differential parameters with implicit ideal \id. Given a nonzero linear differential polynomial $A$ in \id we give necessary and sufficient conditions on $A$ for \cP to be $n-1$ dimensional. We prove the existence of a linear perturbation \cP_{\phi} of \cP so that the linear complete differential resultant \dcres_{\phi} associated to \cP_{\phi} is nonzero. A nonzero linear differential polynomial in \id is obtained from the lowest degree term of \dcres_{\phi} and used to provide an implicitization algorithm for \cP