A novel low-voltage reconfigurable ΣΔ modulator for 4G wireless receivers

This paper presents a new adaptable cascade ΣΔ modulator architecture fo r low-voltage multi-stan- dard applications. It uses two reconfiguration strategies: a programmable global resonation and a variable loop-filter order. These techniques are properly com- bined in a novel topology that allows to increase the effec- tive resolution in a given bandwidth, whereas keeping relaxed output swing requirements and high robustness to mismatch and to non-linearities of the amplifiers. Time-domain simulations incl uding the main circuit-level non-idealities are shown to demonstrate the benefits of the presented modulator when it is configured to cope with the requirements of GSM, UMTS, WLAN and Wi-Max.España, Ministerio de Educación y Ciencia TEC2007-67247-C02-01/MICEspaña, Ministerio de Innovación, Ciencia y Empresa, Junta de Andalucía TIC-253

Un método para validar sistemas de puntos basados en modelos de regresión logística para predecir eventos binarios con la metodología bootstrap y a través de una app para smartphone

Para emplear un sistema de puntos basado en un modelo de regresión logística para predecir un evento binario en una determinada población, es necesaria su validación. Para ello, debemos tener un tamaño muestral suficiente y aplicar las técnicas matemáticas recomendadas por los consensos internacionales. En lo referente al primer punto, se ha recomendado tener un tamaño muestral con al menos 100 eventos y 100 no eventos, independientemente del modelo que estemos validando. Sin embargo, estudios científicos han demostrado que ciertos factores influyen sobre este tamaño, por lo que parece que no tiene mucho sentido tener un valor fijo para este propósito. En consecuencia, en esta tesis doctoral se ha desarrollado un algoritmo para calcular el tamaño muestral en sistemas de puntos obtenidos a través de modelos de regresión logística. Este algoritmo se basa en métodos utilizados ampliamente en la literatura científica, como son la curva ROC o el bootstrapping. Con respecto al segundo y último punto, la forma más correcta de ello es calcular a través de bootstrapping la discrimación y la calibración. La discriminación se puede abordar a través del área bajo la curva ROC y la calibración mediante la representación del gráfico de calibración suavizado (método más recomendado). Esto no es una tarea sencilla, por lo que se plantea la elaboración de una metodología para construir una aplicación para teléfono móvil en Android que la realice. Ambos métodos se han aplicado sobre un conjunto de datos simulados perteneciente a un modelo para predecir mortalidad en las Unidades de Cuidados Intensivos. De esta forma se puede comprender cada una de las etapas, con el fin de poder aplicarse para otros sistemas de puntos para predecir eventos binarios

Simulation-based high-level synthesis of Nyquist-rate data converters using MATLAB/SIMULINK

This paper presents a toolbox for the simulation, optimization and high-level synthesis of Nyquist-rate Analog-to-Digital (A/D) and Digital-to-Analog (D/A) Converters in MATLAB®. The embedded simulator uses SIMULINK® C-coded S-functions to model all required subcircuits including their main error mechanisms. This approach allows to drastically speed up the simulation CPU-time up to 2 orders of magnitude as compared with previous approaches - based on the use of SIMULINK® elementary blocks. Moreover, S-functions are more suitable for implementing a more detailed description of the circuit. For all subcircuits, the accuracy of the behavioral models has been verified by electrical simulation using HSPICE. For synthesis purposes, the simulator is used for performance evaluation and combined with an hybrid optimizer for design parameter selection. The optimizer combines adaptive statistical optimization algorithm inspired in simulated annealing with a design-oriented formulation of the cost function. It has been integrated in the MATLAB/SIMULINK® platform by using the MATLAB® engine library, so that the optimization core runs in background while MATLAB® acts as a computation engine. The implementation on the MATLAB® platform brings numerous advantages in terms of signal processing, high flexibility for tool expansion and simulation with other electronic subsystems. Additionally, the presented toolbox comprises a friendly graphical user interface to allow the designer to browse through all steps of the simulation, synthesis and post-processing of results. In order to illustrate the capabilities of the toolbox, a 0.13)im CMOS 12bit@80MS/s analog front-end for broadband power line communications, made up of a pipeline ADC and a current steering DAC, is synthesized and high-level sized. Different experiments show the effectiveness of the proposed methodology.Ministerio de Ciencia y Tecnología TIC2003-02355RAICONI

Design issues and experimental characterization of a continuously-tuned adaptive CMOS LNA

This paper presents the design implementation and experimental characterization of an adaptive Low Noise Amplifier (LNA) intended for multi-standard Radio Frequency (RF) wireless transceivers. The circuit —fabricated in a 90-nm CMOS technology— is a two-stage inductively degenerated common-source topology that combines PMOS varactors with programmable load to make the operation of the circuit continuously tunable. Practical design issues are analyzed, considering the effect of circuit parasitics associated to the chip package and integrated inductors, capacitors and varactors. Experimental measurements show a continuous tuning of NF and Sparameters within the 1.75-2.23GHz band, featuring NF19.6dB and IIP3> −9.8dBm, with a power dissipation < 23mW from a 1-V supply voltage.Ministerio de Ciencia e Innovación (FEDER) TEC2007-67247-C02-01/MICJunta de Andalucía, Consejo Regional de Innovación, ciencia y empresa TIC-253

The cluster model: A simulation of the aerogel structure as a hierarchically-ordered arrangement of randomly packed spheres

A new structural model based on the premises widely used for describing the structure of aerogels has been introduced. These structures have been described as an assemblage of randomly-packed spheres in several hierarchically-ordered levels. A new algorithm has been developed for constructing our models from these premises using computer simulation. Subsequently, several applications have been simulated to characterize real systems, obtaining textural parameters such as the specific surface area, specific porous volume or the apparent density of the systems, based on the Monte Carlo technique and on geometrical considerations. The object of these is to test the ability of the models to explain the structure of some real aerogels. This Cluster Model has also been applied as an initial approach to the study of the mechanical properties of aerogels. Results support the general conclusion that these models are useful for explaining the structure of aerogels.Ministerio de Ciencia y Tecnología MAT2002-00859Junta de Andalucía TEP 011

Nanostructured sonogels

Acoustic cavitation effects in sol-gel liquid processing permits to obtain nanostructured materials, with size-dependent properties. The so-called "hot spots" produce very high temperatures and pressures which act as nanoreactors. Ultrasounds force the dissolution and the reaction stars. The products (alcohol, water and silanol) help to continue the dissolution, being catalyst content, temperature bath and alkyl group length dependent. Popular choices used in the preparation of silica-based gels are tetramethoxysilane (TMOS), Si(OCH3)4 and tetraethoxysilane (TEOS), Si(OC 2H5)4. The resultant "sonogels" are denser gels with finer and homogeneous porosity than those of classic ones. They have a high surface/volume ratio and are built by small particles (1 nm radius) and a high cross-linked network with low -OH surface coverage radicals. In this way a cluster model is presented based on randomly-packed spheres in several hierarchical levels that represent the real sonoaerogel. Organic modified silicates (ORMOSIL) were obtained by supercritical drying in ethanol of the corresponding alcogel producing a hybrid organic/inorganic aerogel. The new material takes the advantages of the organic polymers as flexibility, low density, toughness and formability whereas the inorganic part contributes with surface hardness, modulus strength, transparency and high refractive index. The sonocatalytic method has proven to be adequate to prepare silica matrices for fine and uniform dispersion of CdS and PbS quantum dots (QDs), which show exciton quantum confinement. We present results of characterization of these materials, such as nitrogen physisorption, small angle X-ray/neutrons scattering, electron microscopy, uniaxial compression and nanoindentation. Finally these materials find application as biomaterials for tissue engineering and for CO2 sequestration by means the carbonation reaction.Ministerio de Ciencia y Tecnología MAT2005-158

Prioritization of olive breeding objectives in Spain: Analysis of a producers and researchers survey

Aim of study: Trait prioritization of potential olive (Olea europaea L.) breeding objectives has been evaluated in this work from two surveys to researchers working on olive and olive producers / orchard managers.Area of study: Olive growing area in Andalusia (South of Spain)Material and methods: Twenty-five breeding objectives were associated to plant growth, fructification, oil content and composition, resistance to pest and disease and tolerance to soil and climatic conditions. Two assessment methods were applied (ranking and rating), showing similar results in both the researchers and producers surveys.Main results: Higher productivity was the objective with the highest score, followed by Verticillium wilt resistance and higher oil content. After them, tolerance to water stress and resistance to Xylella fastidiosa were among the preferred objectives. Conversely, the least preferred objectives were late harvesting, high fruit size and tolerance to water lodging and calcareous soils. In the producers’ survey, results have been consistent among the different types of orchards and farmers’ characteristics. It is also interesting to notice that more than 50% of the producers expressed their willingness to orchard enlargement or renewal in the three coming years and 25% of them would change the olive cultivar. They would be willing to pay an average 43% overprice for new cultivar fulfilling their requirements and 75% would support the use of genetic modified olives.Research highlights: These results should be considered to analyze the scope of current breeding programs and define the main criteria to be considered for future works aiming at developing new olive cultivars

Efficient Hybrid Continuous-Time/Discrete-Time Cascade Modulators for Wideband Applications

This paper analyses the use of hybrid continuous-time/discrete-time cascade ΣΔ modulators for the implementation of power-efficient analog-to-digital converters in broadband wireless communication systems. Two alternative implementations of multi-rate cascade architectures are studied and compared with conventional single-rate continuous-time topologies, taking into account the impact of main circuit-level error mechanisms, namely: mismatch, finite dc gain and gain-bandwidth product. In all cases, closed-form design equations are derived for the nonideal in-band noise power of all ΣΔ modulators under study, providing analytical relationships between their system-level performance and the corresponding circuit-level error parameters. Theoretical predictions match simulation results, showing that the lowest performance degradation is obtained by a new kind of multi-rate hybrid ΣΔ modulator, in which the front-end (continuous-time) stage operates at a higher rate than the back-end (discrete-time) stages. As a case study, the design of a hybrid GmC/switched-capacitor fourth-order (two-stage, 4-bit) cascade ΣΔ modulator is discussed to illustrate the potential benefits of the presented approachMinisterio de Economía y Competitividad TEC2010-14825/MI