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  • Optimization of WPT efficiency using a conjugate load in non-impedance matched systems.

     Chabalko, Matthew; Alarcon Cot, Eduardo Jose; Bou Balust, Elisenda; Ricketts, David S.
    IEEE International Symposium on Antennas and Propagation
    p. 645-646
    DOI: 10.1109/APS.2014.6904653
    Presentation's date: 2014-07-06
    Presentation of work at congresses

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    Maximum power transfer and maximum efficiency are two important design constraints in wireless power transfer applications. Several works have investigated the proper load and impedance match conditions to optimize either efficiency or power transfer. In this paper we show that the optimal load for maximum power transfer and maximum efficiency is the same (a conjugate matched load) when the source resistance is zero. This is important, as many WPT systems have a relatively low, unknown source impedance. Since the optimal load for both efficiency and power is the same as the source impedance approaches zero, the designer can use a bi-conjugate load for a near optimal design for both maximum power and efficiency. As the source impedance becomes significant, the bi-conjugate matched system provides higher power, but at the expense of lower efficiency. Maximum efficiency is achieved with a non-bi-conjugate load, when the source impedance is non-negligible.

  • Advances in non-radiative resonant inductive coupling wireless power transfer: a comparison of alternative circuit and system models driven by emergent applications

     Bou Balust, Elisenda; Sedwick, Raymond; Hu, Patrick; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 2037-2040
    DOI: 10.1109/ISCAS.2014.6865565
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high efficiencies at large distances compared to the transmitting element dimensions, thereby increasing the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary field of research, different approaches have been proposed to predict the behaviour of these systems from the physical theory of resonators (coupled-mode theory) and circuit theory. Although the equivalence of these models for a point-to-point link has already been studied together with the performance metrics Power Transferred to the Load (PTL) and Power Transfer Efficiency (PTE), the new challenges and applications of this technology emphasize the necessity of analytical models to predict and assess the behavior of Multiple Input - Multiple Output (MIMO) links. In this article we revisit the current analytical models from the MIMO perspective, derive the analytical equations for the equivalent performance metrics PTE and PTL and demonstrate how to maximize them in a non-radiative resonant wireless power transfer link from a circuit-centric point of view, providing design guidelines in terms of optimal source and load impedances. This work concludes with a prospective discussion on open challenges of WPT. © 2014 IEEE.

  • Unveiling nonlinear dynamics in resonant inductively coupled wireless power transfer

     Bou Balust, Elisenda; El Aroudi, Abdelali; Fisher, Peter; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 2612-2615
    DOI: 10.1109/ISCAS.2014.6865708
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    Coupled magnetic resonance is considered to be a key enabling technology for mid-range wireless power transfer. Models and systems have hitherto considered linear resonators as underlying dynamics, thereby limiting practical deployability due to the extreme sensitivity in front of parameter mismatch and resonance detuning. In this work, structural nonlinear modeling of constituent elements of the resonant link-resonant coils- is considered to unveil the existence of nonlinear dynamic regimes. The methodology considered to explore the nonlinear behavior is based on a behavioral model consisting of state equations, Floquet theory and Filippov method to study the stability of the periodic regime through the associated monodromy matrix. The ultimate aim of the investigation is a design-oriented parameter space exploration which characterizes the border of occurrence of the different dynamic modes in wireless power transfer links. © 2014 IEEE.

  • Circuit area optimization in energy temporal sparse scenarios for multiple harvester powered systems

     Gomez Cid-fuentes, Raul; Cabellos Aparicio, Alberto; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 2486-2489
    DOI: 10.1109/ISCAS.2014.6865677
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    Multi-source energy harvesters are gaining interest as a robust alternative to power wireless sensors, since the sensor node can maintain its operation regardless of the fact that one of its energy sources might be temporarily unavailable. Interestingly, and less explored, when the energy availability of the energy sources present large temporal variations, combining multiple energy sources reduce the overall sparsity. As a result, the performance of a multiple energy harvester powered sensor node is significantly better compared to a single energy source which harvests the same amount of energy. In this context, a circuit area optimization framework for multiple source energy harvesting powered systems is proposed. This framework takes advantage of this improvement in performance to provide the optimal amount of energy harvesters, the requirements of each energy harvester and the required energy buffer capacity, such that the overall area or volume is minimized. As the results show, by conducting a joint design of the energy harvesters and the energy buffer, the overall area or volume of a sensor node can be significantly reduced. © 2014 IEEE.

  • Nonlinear dynamics of an ambient noise driven array of coupled graphene nanostructured devices for energy harvesting

     El Aroudi, Abdelali; Lopez Suarez, Miquel; Alarcon Cot, Eduardo Jose; Rurali, Riccardo; Abadal, Gabriel
    International Conference on Structural Dynamics and Diagnosis
    p. 01001-1-01001-4
    DOI: 10.1051/matecconf/20141601001
    Presentation's date: 2014-05
    Presentation of work at congresses

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    Nonlinearities have been shown to play an important role in increasing the extracted energy of energy harvesting devices at the macro and micro scales. Vibration-based energy harvesting on the nano scale has also received attention. In this paper, we characterize the nonlinear dynamical behavior of an array of three coupled strained nanostructured graphene for its potential use in energy harvesting applications. The array is formed by three compressed vibrating membrane graphene sheet subject to external vibrational noise excitation. We present the continuous time dynamical model of the system in the form of a double-well three degree of freedom system. Random vibrations are considered as the main ambient energy source for the system and its performances in terms of the probability density function, RMS or amplitude value of the position, FFT spectra and state plane trajectories are presented in the steady state non-equilibrium regime when the noise level is considered as a control parameter.

  • Nonlinear dynamics and bifurcation behavior of a 2-DOF spring resonator with end stopper for energy harvesting

     El Aroudi, Abdelali; Blokhina, Elena; O'Connell, D.; Fu, B; Frizzell, R; Feely, Orla; Alarcon Cot, Eduardo Jose
    International Conference on Structural Dynamics and Diagnosis
    p. 08006-1-08006-6
    DOI: 10.1051/matecconf/20141608006
    Presentation's date: 2014-05
    Presentation of work at congresses

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    In this paper, the model of a two-degree-of-freedom (2-DOF) spring resonator with end stopper for an energy harvesting application is presented. Then we characterize its nonlinear dynamical behavior by numerical simulations when some suitable parameters are varied. The system is formed by two resonators subject to external vibrational excitation and with an end stopper. We present the continuous time dynamical model of the system in the form of a switched fourth order differential equation. Harmonic vibrations are considered as the main ambient energy source for the system and its frequency response representing the RMS value of the displacement is first computed. The dynamical behavior is unveiled by computing state-space trajectories, timedomain series and FFT spectra and frequency response as the excitation amplitude is varied.

  • Low cost photovoltaic array emulator design for the test of PV grid-connected inverters

     Chavarria Roe, Javier; Biel Sole, Domingo; Guinjoan Gispert, Francisco; Poveda Lopez, Alberto; Masana Nadal, Francisco; Alarcon Cot, Eduardo Jose
    International Multi-Conference on Systems, Signals and Devices
    p. 1-6
    DOI: 10.1109/SSD.2014.6808860
    Presentation's date: 2014-02-11
    Presentation of work at congresses

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    This paper presents a low cost photovoltaic array emulator design based on a DC-DC Boost converter. This design arises from the need to study in the laboratory new PV inverters based on SiC devices in order to improve their performances. The lack of space for installation of real photovoltaic panels and the high costs of the commercial emulators require of alternative systems which allow the reproduction of the characteristic curves of the panels as well as their dependence on changing environmental conditions. The emulator design is applied to a full-bridge single phase grid-connected inverter. Simulation results are provided to confirm the proper operation of the PV emulator. © 2014 IEEE.

  • Performance analysis of dual-frequency buck converter for integrated power management

     Shirmohammadli, V.; Saberkari, Alireza; Alarcon Cot, Eduardo Jose
    Power Electronics, Drive Systems and Technologies Conference
    p. 402-407
    DOI: 10.1109/PEDSTC.2014.6799409
    Presentation's date: 2014-02
    Presentation of work at congresses

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    The use of dual-frequency (DF) buck converter architecture consisting of a merged structure of high and low frequency buck cells is presented as a candidate topology for integrated power management to obtain favorable tradeoffs in terms of efficiency, switching ripple, and bandwidth. It is shown that having two degrees of freedom in designing the DF buck helps to achieve high efficiency and low output ripples, simultaneously. A comparison analysis is done with regards to the aforementioned performance indexes with the standard and three-level buck converters and the results are validated in HSPICE in a 0.35 µm CMOS process.

  • Class E2 resonant non-radiative wireless power transfer link: a design-oriented joint circuit-system co-characterization approach

     Bou Balust, Elisenda; Nagashima, Tomoharu; Sekiya, Hiroo; Alarcon Cot, Eduardo Jose
    International Multi-Conference on Systems, Signals and Devices
    p. 1-4
    DOI: 10.1109/SSD.2014.6808902
    Presentation's date: 2014-02-11
    Presentation of work at congresses

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    Resonant Inductive CouplingWireless Power Transfer is a key technology to provide an efficient and harmless wireless energy channel to consumer electronics, biomedical implants and wireless sensor networks. Many applications have been proposed for this technology, but the interplay between the Resonant Inductive Coupling magnetic link and the power electronics front-end is still unclear. In this paper, we propose a design-oriented joint circuit-system approach to design a high-efficiency resonant inductive coupling wireless power transfer link embedded in a class E2 DC-DC converter. © 2014 IEEE.

  • Transferencia de energía inalámbrica: acoplamiento inductivo resonante

     Poveda López, Alberto; Vidal Lopez, Eva Maria; Martínez García, Herminio; Alarcon Cot, Eduardo Jose
    Competitive project

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  • On the Scalability Limits of Communication Networks to the Nanoscale  Open access

     Llatser Marti, Ignacio
    Universitat Politècnica de Catalunya
    Theses

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    Los nanosistemas, sistemas integrados con un tamaño total de unos pocos micrómetros, son capaces de interactuar en la nanoescala, pero su corto radio de acción limita su utilidad en escenarios prácticos. Las nanoredes, que surgen de la interconexión de nanosistemas, amplían su ámbito de operación permitiendo la comunicación entre nanosistemas, aumentando de esta forma sus aplicaciones potenciales. Con el fin de dotar de capacidades de comunicación a los nanosistemas, su subsistema de comunicación debe reducirse a unos pocos micrómetros. Existen dudas sobre la viabilidad de miniaturizar las antenas metálicas actuales a un tamaño tan pequeño, especialmente porque su frecuencia de resonancia sería extremadamente alta (en el espectro óptico), lo que causaría a una gran atenuación de las ondas radiadas. Como alternativa, se han propuesto dos nuevos paradigmas para implementar comunicaciones inalámbricas entre nanosistemas: las comunicaciones moleculares y las comunicaciones inalámbricas basadas en grafeno. Por un lado, las comunicaciones moleculares consisten en el intercambio de moléculas entre nanosistemas, inspirado en la comunicación entre células vivas. En las comunicaciones moleculares basadas en difusión (DMC), las moléculas emitidas se propagan por el medio mediante un proceso de difusión hasta que alcanzan el receptor. Por otro lado, el grafeno (una lámina de átomos de carbono de un átomo de espesor) permite implementar antenas de grafeno plasmónicas, o grafenas. Debido a efectos plasmónicos, grafenas con un tamaño de unos pocos micrómetros radian ondas en la banda de terahercios, dando lugar al paradigma de las comunicaciones inalámbricas basadas en grafeno (GWC). Para averiguar cómo escalan las redes de comunicación a medida que se reducen sus dimensiones, esta tesis se presenta un análisis de la escalabilidad de las redes de comunicaciones hacia la nanoescala, siguiendo un modelo general con la menor cantidad posible de hipótesis. Hemos propuesto dos esquemas de detección en DMC: detección de amplitud y detección de energía. Hemos identificado importantes métricas de rendimiento y calculado su escalabilidad con respecto a la distancia de transmisión, que difiere significativamente respecto a las comunicaciones inalámbricas tradicionales. Estas nuevas tendencias de escala requieren el diseño de nuevos protocolos de red especialmente adaptados a las redes de DMC. El análisis de la propagación de ondas plasmónicas en grafenas permite determinar sus propiedades de radiación. En particular, la frecuencia de resonancia de las grafenas no sólo es más baja que en antenas metálicas, sino que también aumenta más lentamente a medida que reducimos su longitud. Por otra parte, la frecuencia de resonancia de las grafenas puede ser ampliamente controlada en función de parámetros como las dimensiones de la grafena, el tiempo de relajación del grafeno y el potencial químico. Además, proponemos un montaje experimental que permite la medición de grafenas alimentadas con una fuente fotoconductora. También hemos analizado los efectos de la absorción molecular en el canal de terahercios a corto alcance, el escenario de operación de las grafenas. La absorción molecular es un proceso por el cual moléculas presentes en la atmósfera absorben parte de la energía de las ondas radiadas por las grafenas, degradando su rendimiento. Hemos cuantificado esta degradación derivando parámetros de rendimiento en este escenario, que muestran novedosas tendencias de escalabilidad en función de la distancia de transmisión. Por último, hemos encontrado que la capacidad de canal de GWC escala mejor a medida que el tamaño de la antena se reduce con respecto a las comunicaciones inalámbricas tradicionales. En consecuencia, las GWC requerirán una potencia de transmisión más baja para lograr un cierto rendimiento. Estos resultados establecen un marco general que puede servir de guía para diseñar las futuras redes de comunicaciones inalámbricas entre nanosistemas.

    Nanosystems, integrated systems with a total size of a few micrometers, are capable of interacting at the nanoscale, but their short operating range limits their usefulness in practical macro-scale scenarios. Nanonetworks, the interconnection of nanosystems, will extend their range of operation by allowing communication among nanosystems, thereby greatly enhancing their potential applications. In order to integrate communication capabilities into nanosystems, their communication subsystem needs to shrink to a size of a few micrometers. There are doubts about the feasibility of scaling down current metallic antennas to such a small size, mainly because their resonant frequency would be extremely high (in the optical domain) leading to a large free-space attenuation of the radiated EM waves. In consequence, as an alternative to implement wireless communications among nanosystems, two novel paradigms have emerged: molecular communication and graphene-enabled wireless communications. On the one hand, molecular communication is based on the exchange of molecules among nanosystems, inspired by communication among living cells. In Diffusion-based Molecular Communication (DMC), the emitted molecules propagate throughout the environment following a diffusion process until they reach the receiver. On the other hand, graphene, a one-atom-thick sheet of carbon atoms, has been proposed to implement graphene plasmonic RF antennas, or graphennas. Graphennas with a size in the order of a few micrometers show plasmonic effects which allow them to radiate EM waves in the terahertz band. Graphennas are the enabling technology of Graphene-enabled Wireless Communications (GWC). In order to answer the question of how communication networks will scale when their size shrinks, this thesis presents a scalability analysis of the performance metrics of communication networks to the nanoscale, following a general model with as few assumptions as possible. In the case of DMC, two detection schemes are proposed: amplitude detection and energy detection. Key performance metrics are identified and their scalability with respect to the transmission distance is found to differ significantly from the case of traditional wireless communications. These unique scaling trends present novel challenges which require the design of novel networking protocols specially adapted to DMC networks. The analysis of the propagation of plasmonic waves in graphennas allows determining their radiation performance. In particular, the resonant frequency of graphennas is not only lower than in metallic antennas, but it also increases more slowly as their length is reduced to the nanoscale. Moreover, the study of parameters such as the graphenna dimensions, the relaxation time of graphene and the applied chemical potential shows the tunability of graphennas in a wide frequency range. Furthermore, an experimental setup to measure graphennas based on feeding them by means of a photoconductive source is described. The effects of molecular absorption in the short-range terahertz channel, which corresponds to the expected operating scenario of graphennas, are analyzed. Molecular absorption is a process in which molecules present in the atmosphere absorb part of the energy of the terahertz EM waves radiated by graphennas, causing impairments in the performance of GWC. The study of molecular absorption allows quantifying this loss by deriving relevant performance metrics in this scenario, which show novel scalability trends as a function of the transmission distance with respect to the case of free-space propagation. Finally, the channel capacity of GWC is found to scale better as the antenna size is reduced than in traditional wireless communications. In consequence, GWC will require lower transmission power to achieve a given performance target. These results establish a general framework which may serve designers as a guide to implement wireless communication networks among nanosystems.

  • UPCSAT-1, demostrador CubeSat para observación terrestre

     Jove Casulleras, Roger; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Bou Balust, Elisenda; Ramos Castro, Juan Jose; Alarcon Cot, Eduardo Jose; Alonso Arroyo, Alberto
    Congreso de la Asociación Española de Teledetección
    p. 49-52
    Presentation's date: 2013-10
    Presentation of work at congresses

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    UPCSat-1, es el primer proyecto de la Universitat Politécnica de Catalunya para construir y lanzar un pico- satélite. El objetivo principal de este proyecto es construir, ensamblar, testear y poner en órbita baja terrestre (LEO) un sensor óptico y un sensor de oxígeno monoatómico entre otros demostradores tecnológicos. Empezado en 2007 y actualmente en fase de integración, el satélite UPCSat-1 pretende demostrar la validez de la plataforma y las tecnologías que incorpora. Su objetivo es adquirir el know-how para la fabricación de CubeSats para preparar misiones más complejas en un futuro cercano. Por otro lado el proyecto tiene un fuerte componente educacional puesto que algunos de los subsistemas han sido desarrollados por nuestros estudiantes a través de sus proyectos finales de carrera. Se espera el lanzamiento para antes de 2015.

  • Inductively coupled wireless power transfer with Class-E2 DC-DC converter

     Nagashima, Tomoharu; Inoue, Kazuhide; Wei, Xiuqin; Bou, Elisenda; Alarcon Cot, Eduardo Jose; Sekiya, Hiroo
    European Conference on Circuit Theory and Design
    p. 1-4
    DOI: 10.1109/ECCTD.2013.6662278
    Presentation's date: 2013-09-08
    Presentation of work at congresses

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    This paper proposes an inductive coupled wireless power transfer (WPT) system with class-E2 dc-dc converter along with its design procedure. The proposed WPT system can achieve high power-conversion efficiency at high frequencies because it satisfies the class-E zero-voltage switching and zero-derivative-voltage switching conditions on both the inverter and the rectifier. By using the class-E inverter as a transmitter and the class-E rectifier as a receiver, high power-delivery efficiency can be achieved in the designed WPT system. By using a numerical design procedure proposed in the previous work, it is possible to design the WPT system without considering the impedance matching for satisfying the class-E ZVS/ZDS conditions. The experimental results of the design example showed the overall efficiency of 85:1%at 100Woutput power and 200 kHz operating frequency.

  • 8th Google Faculty Reserach Award

     Alarcon Cot, Eduardo Jose; Camps Carmona, Adriano Jose; Ramos Castro, Juan Jose
    Award or recognition

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  • Magnetic characterization of interfering objects in resonant inductive coupling wireless power transfer

     Bou Balust, Elisenda; Vidal, D.; Sedwick, Raymond; Alarcon Cot, Eduardo Jose
    Progress in Electromagnetics Research Symposium
    p. 1554-1559
    Presentation's date: 2013-08-16
    Presentation of work at congresses

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    Resonant Inductive Coupling (RIC) Wireless Power Transfer is a key technology to provide an efficient and harmless wireless energy channel to consumer electronics, biomedical implants and wireless sensor networks. However, there are two factors that are limiting the applicability of this technology: the effects of distance variation between transmitter and receiver and the effects of interfering objects. While distance variation in WPT has been thoroughly studied, the effects of conductive interfering objects in resonant inductive coupling links are still unclear. When a conductive element is in the vicinity of a RIC link, both the transmitter and the receiver can experiment a change on their resonant frequencies as well as their impedances. This can greatly affect the effciency of such WPT link causing it to a) make the transmitter and/or receiver act as a pass-band filter and b) loose part of the transmitter magnetic field through coupling to the interfering object. Depending on the natural resonant frequency of the object and the distances between this object and the transmitter and receiver antennas, this can affect significantly the RIC wireless power transfer link. In this article, we characterize the Magnetic behavior of a resonant inductive coupled link in the presence of a conductive interfering object using a Finite Element Field Solver (FEKO). Several distances between interference and transmitter/receiver are analyzed providing a design space exploration and applicability study of this link.

  • Estudio y simulación de MOSFETs de carburo de silicio (SiC) mediante PSIM para un inversor fotovoltaico en puente completo conectado a red

     Chavarria Roe, Javier; Biel Sole, Domingo; Guinjoan Gispert, Francisco; Poveda Lopez, Alberto; Alarcon Cot, Eduardo Jose; Massana, Francisco
    Seminario Anual de Automática, Electrónica Industrial e Instrumentación
    p. 50
    Presentation's date: 2013-07-11
    Presentation of work at congresses

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    El presente artículo muestra, mediante simulación PSIM, el impacto de la utilización de MOSFETs de Carburo de Silicio (SiC) en la eficiencia de inversores fotovoltaicos en puente completo conectados a red. Las simulaciones presentadas utilizan la facilidad ¿Device Database Editor¿ para construir modelos de MOSFET tanto de Si como de SiC y comparan diversos parámetros como la eficiencia o el rizado de la corriente de salida. Estas simulaciones también permiten establecer un método de diseño de la frecuencia de conmutación y del inductor de salida del inversor.

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    Chaotic behaviour in on-chip automatic tuning loops for continuous-time filters  Open access

     Martínez García, Herminio; El Aroudi, Abdelali; Alarcon Cot, Eduardo Jose; Poveda Lopez, Alberto
    Seminario Anual de Automática, Electrónica Industrial e Instrumentación
    p. 1-4
    Presentation's date: 2013-07-11
    Presentation of work at congresses

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    Continuous-time filters (CTF) with automatic tuning loops are nonlinear feedback systems with potential instability. While an appropriate small signal linear dynamic modeling of the tunable filter should be obtained for design purpose, its ability to predict the real nonlinear dynamic behavior of the system is limited. In order to overcome this problem, a general and systematic procedure is used to obtain a large signal nonlinear model. The obtained model can accurately predict nonlinear phenomena such as bifurcations and chaotic behavior. From this model, some numerical simulations results are presented in this paper. As far as the authors know, the observation of these phenomena in CTF with tuning loops has not been previously presented. Thus, the results obtained in this work can provide some help to obtain improved controllers (with higher bandwidth and better performance) for the two involved control loops.

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    Designing CDIO capstone projects: a systems thinking approach  Open access

     Alarcon Cot, Eduardo Jose; Bou Balust, Elisenda; Camps Carmona, Adriano Jose; Bragos Bardia, Ramon; Oliveras Verges, Albert; Pegueroles Valles, Josep Rafel; Sayrol Clols, Elisa; Marques Acosta, Fernando
    International CDIO Conference
    p. 1-9
    Presentation's date: 2013-06-10
    Presentation of work at congresses

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    Given the all-pervasiveness of Systems thinking -which consists of thinking about things as systems- as a way of reasoning, in this work we will describe its application to make an interpretation of how to conceive and design a final year CDIO capstone course. Both the student teamwork structure as well as the complex engineering system itself addressed in the project are described in terms of entities, links, form and function, thereby pointing out their formal and functional interaction. The ultimate goal of the Systems thinking perspective is, given the necessary ingredients, to try maximizing the chances of the emergence of a fruitful capstone course, namely a culminating project that yields a set of students qualified to CDIO complex engineering systems.

    Given the all-pervasiveness of Systems thinking -which consists of thinking about things as systemsas a way of reasoning, in this work we will describe its application to make an interpretation of how to conceive and design a final year CDIO capstone course. Both the student teamwork structure as well as the complex engineering system itself addressed in the project are described in terms of entities, links, form and function, thereby pointing out their formal and functional interaction. The ultimate goal of the Systems thinking perspective is, given the necessary ingredients, to try maximizing the chances of the emergence of a fruitful capstone course, namely a culminating project that yields a set of students qualified to CDIO complex engineering systems.

  • Maximizing efficiency through impedance matching from a circuit-centric model of non-radiative resonant wireless power transfer

     Bou Balust, Elisenda; Sedwick, Raymond; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 29-32
    DOI: 10.1109/ISCAS.2013.6571774
    Presentation's date: 2013-05-21
    Presentation of work at congresses

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    Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high efficiencies (above 40%) at large distances compared to the transmitting element dimensions, thereby exponentially increasing the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary field, different approaches have been proposed to predict the behaviour of these systems from the physical theory of resonators (coupled-mode theory), reflected load theory and circuit theory. Also, there is in this field a heterogeneous definition of metrics without a clear optimization process. In this article we unify the different metrics and demonstrate how to maximize the power transfer efficiency in a non-radiative resonant wireless power transfer link from a circuit-centric point of view providing design guidelines in terms of optimal load impedance, optimal source impedance and optimal distance between coils.

  • Interference analysis on resonant inductive coupled wireless power transfer

     Bou Balust, Elisenda; Alarcon Cot, Eduardo Jose; Sedwick, Raymond; Fisher, Peter
    IEEE International Symposium on Circuits and Systems
    p. 2783-2786
    DOI: 10.1109/ISCAS.2013.6572456
    Presentation's date: 2013-05-22
    Presentation of work at congresses

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    Resonant Inductive Coupling Wireless Power Transfer is a key technology to provide an efficient and harmless wireless energy channel to consumer electronics, biomedical implants and wireless sensor networks. However, there are two factors that are limiting the applicability of this technology: the effects of distance variation between transmitter and receiver and the effects of interfering objects. While distance variation in WPT has been thoroughly studied, the effects of interfering objects in resonant inductive coupling links are still unclear. In this article we propose a new circuit-based analytical model that predicts the behavior of a resonant inductive coupled link in the presence of interfering objects and verify the obtained results with a Finite Element Field Solver.

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    Output-capacitorless CMOS LDO regulator based on high slew-rate current-mode transconductance amplifier  Open access

     Saberkari, Alireza; Fathipour, Rasoul; Martínez García, Herminio; Poveda Lopez, Alberto; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 1484-1487
    DOI: 10.1109/ISCAS.2013.6572138
    Presentation's date: 2013-05-21
    Presentation of work at congresses

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    A low quiescent current output-capacitorless CMOS LDO regulator based on a high slew-rate current-mode transconductance amplifier (CTA) as an error amplifier is presented. Load transient characteristic of the proposed LDO is improved even at low quiescent currents, by using a local common-mode feedback (LCMFB) in the proposed CTA. This provides an increase in the order of transfer characteristic of the circuit, thereby enhancing the slew-rate at the gate of pass transistor. The proposed CTA-based LDO topology has been designed and post-layout simulated in HSPICE, in a 0.18 µm CMOS process to supply a load current between 0-100 mA. Postlayout simulation results reveal that the proposed LDO is stable without any internal compensation strategy and with on-chip output capacitor or lumped parasitic capacitances at the output node between 10-100 pF.

    A low quiescent current output-capacitorless CMOS LDO regulator based on a high slew-rate current-mode transconductance amplifier (CTA) as an error amplifier is presented. Load transient characteristic of the proposed LDO is improved even at low quiescent currents, by using a local common-mode feedback (LCMFB) in the proposed CTA. This provides an increase in the order of transfer characteristic of the circuit, thereby enhancing the slew-rate at the gate of pass transistor. The proposed CTA-based LDO topology has been designed and post-layout simulated in HSPICE, in a 0.18 μm CMOS process to supply a load current between 0-100 mA. Postlayout simulation results reveal that the proposed LDO is stable without any internal compensation strategy and with on-chip output capacitor or lumped parasitic capacitances at the output node between 10-100 pF.

  • Area and laser power scalability analysis in photonic networks-on-chip

     Abadal Cavalle, Sergi; Cabellos Aparicio, Alberto; Lazaro Villa, Jose Antonio; Nemirovsky, Mario; Alarcon Cot, Eduardo Jose; Sole Pareta, Josep
    International Conference on Optical Network Design and Modeling
    p. 131-136
    Presentation's date: 2013-04-18
    Presentation of work at congresses

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    In the last decade, the field of microprocessor architecture has seen the rise of multicore processors, which consist of the interconnection of a set of independent processing units or cores in the same chip. As the number of cores per multiprocessor increases, the bandwidth and energy requirements for their interconnection networks grow exponentially and it is expected that conventional on-chip wires will not be able to meet such demands. Alternatively, nanophotonics has been regarded as a strong candidate for chip communication since it could provide high bandwidth with low area and energy footprints. However, issues such as the unavailability of efficient on-chip light sources or the difficulty of implementing all-optical buffering or header processing hinder the development of scalable photonic on-chip networks. In this paper, the area and laser power of several photonic on-chip network proposals is analytically modeled and its scalability is evaluated. Also, a graphene-based hybrid approach is presented

    In the last decade, the field of microprocessor architecture has seen the rise of multicore processors, which consist of the interconnection of a set of independent processing units or cores in the same chip. As the number of cores per multiprocessor increases, the bandwidth and energy requirements for their interconnection networks grow exponentially and it is expected that conventional on-chip wires will not be able to meet such demands. Alternatively, nanophotonics has been regarded as a strong candidate for chip communication since it could provide high bandwidth with low area and energy footprints. However, issues such as the unavailability of efficient on-chip light sources or the difficulty of implementing all-optical buffering or header processing hinder the development of scalable photonic on-chip networks. In this paper, the area and laser power of several photonic on-chip network proposals is analytically modeled and its scalability is evaluated. Also, a graphene-based hybrid wireless/optical-wired approach is presented, aiming at enabling end-to-end photonic on-chip networks to scale beyond thousands of cores

  • Chaos in switching converters for power management: designing for prediction and control

     Rodriguez Vilamitjana, Enric; El Aroudi, Abdelali; Alarcon Cot, Eduardo Jose
    DOI: 10.1007/978-1-4614-2128-3
    Date of publication: 2013-01-15
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  • Reactive power control for voltage support during type C voltage-sags

     Camacho Santiago, Antonio; Castilla Fernandez, Miguel; Miret Tomas, Jaume; Matas Alcala, Jose; Alarcon Cot, Eduardo Jose; Garcia de Vicuña Muñoz de la Nava, Jose Luis; Marti Colom, Pau
    Annual Conference of the IEEE Industrial Electronics Society
    p. 3462-3467
    DOI: 10.1109/IECON.2012.6389343
    Presentation's date: 2012-10-27
    Presentation of work at congresses

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    Chaos controller for switching regulators aiming enhanced design-space towards miniaturization  Open access

     Rodríguez Rodríguez, Enric; El Aroudi, Abdelali; Martínez García, Herminio; Poveda Lopez, Alberto; Iu, H.; Alarcon Cot, Eduardo Jose
    International Symposium on Nonlinear Theory and its Applications
    Presentation's date: 2012-10-25
    Presentation of work at congresses

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    This paper tackles the control of fast-scale instabilities in a buck switching power converter aiming to expand its design-space towards miniaturization. After briefly revisiting the working principle of existing chaos controllers, the paper explores an alternative approach based on amplifying the harmonic at the switching frequency. Numerical simulations show that the proposed controller can concurrently improve both fast-scale and slow-scale stability margins. Finally, the paper proposes a chaos controller combined with an output ripple reduction network and studies their interaction with the aim of achieving both low-ripple and improved stability.

  • Distincio Jaume Vicenç Vives

     Bragos Bardia, Ramon; Alarcon Cot, Eduardo Jose; Camps Carmona, Adriano Jose; Consolacion Segura, Carolina Maria; Oliveras Verges, Albert; Pegueroles Valles, Josep Rafel; Sayrol Clols, Elisa
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  • Resonant pulse-shaping power supply for radar transmitters

     Bell Rodriguez, Miguel Victoria Ramo; Roberg, Michael; Pack, Riley; Garcia Fernandez, Pablo; Alarcon Cot, Eduardo Jose; Popoviç, Zoya; Maksimovic, Dragan
    International Power Electronics and Motion Control Conference
    p. LS5e.31-LS5e.37
    DOI: 10.1109/EPEPEMC.2012.6397484
    Presentation's date: 2012-09
    Presentation of work at congresses

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    The final radiofrequency power amplifier (PA) of a radar transmitter module is a large factor in system efficiency. Typical radar transmitter signals are frequency-modulated with constant-amplitude pulse envelopes in order to optimize efficiency, resulting in spectral broadening and power radiated outside of the radar frequency band. This paper demonstrates a PA with a dynamic power supply which enables high efficiency while reducing the spectral emissions. The resonant pulse-shaping power supply generates a raised-cosine pulse envelope waveform with efficiency greater than 90% and peak envelope power around 6 W. Measured results with a 2.14-GHz GaN power amplifier with an efficiency of 76% at peak power demonstrate over 67% transmitter efficiency.

  • A design-oriented optimization framework for envelope trackers: Application to a sliding-mode control buck converter for EDGE

     Marco Platón, Lázaro; Poveda Lopez, Alberto; Guinjoan Gispert, Francisco; Maksimovic, Dragan; Alarcon Cot, Eduardo Jose
    International Power Electronics and Motion Control Conference
    p. 21-26
    Presentation's date: 2012-09
    Presentation of work at congresses

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  • Graphene-enabled hybrid architectures for multiprocessors: bridging nanophotonics and nanoscale wireless communication

     Abadal Cavalle, Sergi; Cabellos Aparicio, Alberto; Lazaro Villa, Jose Antonio; Alarcon Cot, Eduardo Jose; Sole Pareta, Josep
    International Conference on Transparent Optical Networks
    p. 1-4
    Presentation's date: 2012-07-04
    Presentation of work at congresses

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  • 15è. Premi UPC a la Qualitat en la Docència Universitària

     Bragos Bardia, Ramon; Sayrol Clols, Elisa; Alarcon Cot, Eduardo Jose; Camps Carmona, Adriano Jose; Pegueroles Valles, Josep Rafel; Oliveras Verges, Albert; Consolacion Segura, Carolina Maria
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  • Quorum sensing-enabled amplification for molecular nanonetworks

     Abadal Cavalle, Sergi; Llatser Marti, Ignacio; Alarcon Cot, Eduardo Jose; Cabellos Aparicio, Alberto
    IEEE International Workshop on Molecular and Nano Scale Communication
    p. 6162-6166
    DOI: 10.1109/ICC.2012.6364691
    Presentation's date: 2012-06
    Presentation of work at congresses

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  • Electronically tunable switch¿mode high-efficiency adaptive band-pass filters for energy harvesting applications

     Gómez Cid-Fuentes, Raül; Martínez García, Herminio; Poveda Lopez, Alberto; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 684-687
    DOI: 10.1109/ISCAS.2012.6272125
    Presentation's date: 2012-05-22
    Presentation of work at congresses

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    Wireless Sensor Networks (WSN) present a pending challenge for a complete deployability due to energy requirements. The Self-Powered WSN approach aims to extend the sensor node life by means of Energy Harvesting. The harvested energy presents an erratic behavior in both time and frequency. In this paper, a new concept of switch-mode electronically tunable band-pass filters is presented to adaptively follow the power source variations and to maximize the power transfer. To implement these switch-mode filters, three alternatives are presented. These filter topologies are modeled and evaluated. Additionally, some design guidelines are provided. The results show how these high efficiency topologies present a band-pass behavior whose center frequency can be electronically tuned over one decade. The results target the integration of these highefficiency switch-mode band-pass filters into the future harvesting front-ends.

  • Ripple-based prediction of fast-scale instabilities in current mode controlled switching converters

     Rodríguez Rodríguez, Enric; Martínez García, Herminio; Guinjoan Gispert, Francisco; El Aroudi, Abdelali; Poveda Lopez, Alberto; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 688-691
    DOI: 10.1109/ISCAS.2012.6272126
    Presentation's date: 2012-05-22
    Presentation of work at congresses

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  • Analysis of limit cycles in a PI digitally controlled buck converter

     Bradley, D.; Alarcon Cot, Eduardo Jose; Feely, Orla
    IEEE International Symposium on Circuits and Systems
    p. 628-631
    DOI: 10.1109/ISCAS.2012.6272110
    Presentation's date: 2012-05-23
    Presentation of work at congresses

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    Digital control of power converters has been an area of considerable research interest in recent times. One of the problems which arises in these systems is that of the limit cycle oscillations that occur due to quantization in the feedback loop. This paper investigates the limit cycle oscillations that occur in the digitally controlled version of the buck converter with a proportional-integral controller. The amplitude and frequency of the oscillations that may occur on two duty cycle levels are investigated and related to the controller gain parameters. The analysis shows that it is not possible to guarantee that limit cycle oscillations on two levels will not occur simply by adjusting the gain parameters, and yields a condition which will prevent oscillations on two levels from occurring.

  • Electronically tunable switch-mode high-efficiency adaptive band-pass filters for energy harvesting applications

     Gómez Cid-Fuentes, Raül; Martínez García, Herminio; Poveda Lopez, Alberto; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 684-687
    DOI: 10.1109/ISCAS.2012.6272125
    Presentation's date: 2012-05-21
    Presentation of work at congresses

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  • Fast transient response CFA-based LDO regulator

     Saberkari, Alireza; Martínez García, Herminio; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 3150-3153
    DOI: 10.1109/ISCAS.2012.6271990
    Presentation's date: 2012-05-22
    Presentation of work at congresses

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  • Prospects of graphene-enabled wireless communications

     Llatser Marti, Ignacio; Abadal Cavalle, Sergi; Gómez Cid-Fuentes, Raül; Jornet, Josep Miquel; Cabellos Aparicio, Alberto; Alarcon Cot, Eduardo Jose; Sole Pareta, Josep; Akyildiz, Ian F.
    International Conference on GRAPHENE
    Presentation's date: 2012-04-10
    Presentation of work at congresses

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  • Characterization of graphene-based nano-antennas in the terahertz band

     Llatser Marti, Ignacio; Kremers, Christian; Chigrin, Dmitry N.; Jornet, Josep Miquel; Lemme, Max C.; Cabellos Aparicio, Alberto; Alarcon Cot, Eduardo Jose
    European Conference on Antennas and Propagation
    p. 194-198
    DOI: 10.1109/EuCAP.2012.6206598
    Presentation's date: 2012-03-26
    Presentation of work at congresses

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  • 2012 SAMSUNG Global Research Outreach GIFT

     Alarcon Cot, Eduardo Jose; Cabellos Aparicio, Alberto
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  • Comparison of the resonant frequency in graphene and metallic nano-antennas

     Llatser Marti, Ignacio; Kremers, Christian; Cabellos Aparicio, Alberto; Alarcon Cot, Eduardo Jose; Chigrin, Dmitry N.
    International Workshop on Theoretical and Computational Nanophotonics
    p. 143-145
    DOI: 10.1063/1.4750123
    Presentation's date: 2012
    Presentation of work at congresses

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  • CMOS fast transient low-dropout regulator

     Saberkari, Alireza; Alarcon Cot, Eduardo Jose; Shokouhi, Shahriar B.
    Iranian Conference Electrical Engineering
    p. 105-108
    DOI: 10.1109/IranianCEE.2012.6292333
    Presentation's date: 2012
    Presentation of work at congresses

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    In this paper a fast transient response CFA-based low-dropout regulator (LDO) is introduced. The circuit is stable for 0-100mA output load current and a 1μF output capacitor without any internal compensation. The CFA consists of a voltage follower with output local current-current feedback based on a level-shifted flipped voltage follower (LSFVF) which is instrumental to achieve high regulation and fast transient response. The inverting output buffer stage of the CFA together with current-mirror-based driving of the pass transistor results in high PSRR. Full transistor-level simulation results for an AMS 0.35μm CMOS process design reveal that the proposed LDO dissipates 58μA quiescent current at no-load condition and in worst case conditions has a current efficiency of 99.8%. For a 1μF output capacitor, the maximum output voltage variation to a 0-100mA load transient with rise and fall time of 10 and 100ns is only 2.5mV, and the PSRR is smaller than -58dB over the entire load current range.

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    A comparison of analytical models for resonant inductive coupling wireless power transfer  Open access

     Bou, Elisenda; Alarcon Cot, Eduardo Jose; Gutierrez Cabello, Jorge Luis
    Progress in Electromagnetics Research Symposium
    p. 689-693
    Presentation's date: 2012
    Presentation of work at congresses

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    Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high efficiencies (above 40%) at large distances compared to the antenna dimensions, which has exponentially increased the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary field, different approaches have been proposed to predict the behaviour of these systems from physical theory of resonators, reflected load theory and the circuit point of view. However, the relation between these methods is still obscure. In this article, we compare the results of these models to find the effciency of a Resonant Inductive Coupling WPT system under Steady-State sonditions and to analyze the relation between the optimal load values obtained from this perspectives and the ones obtained using impedance matching techniques.

    Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high e±ciencies (above 40%) at large distances compared to the antenna dimensions, which has exponentially increased the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary ¯eld, di®erent approaches have been proposed to predict the behaviour of these systems from physical theory of resonators, reflected load theory and the circuit point of view. However, the relation between these methods is still obscure. In this article, we compare the results of these models to find the effciency of a Resonant Inductive Coupling WPT system under Steady-State sonditions and to analyze the relation between the optimal load values obtained from this perspectives and the ones obtained using impedance matching techniques.

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    Exploring the physical channel of diffusion-based molecular communication by simulation  Open access

     Llatser Marti, Ignacio; Pascual, Iñaki; Garralda, N.; Cabellos Aparicio, Alberto; Pierobon, Massimiliano; Alarcon Cot, Eduardo Jose; Sole Pareta, Josep
    IEEE Global Communications Conference
    p. 1-5
    DOI: 10.1109/GLOCOM.2011.6134028
    Presentation's date: 2011-12
    Presentation of work at congresses

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    Diffusion-based molecular communication is a promising bio-inspired paradigm to implement nanonetworks, i.e., the interconnection of nanomachines. The peculiarities of the physical channel in diffusion-based molecular communication require the development of novel models, architectures and protocols for this new scenario, which need to be validated by simulation. With this purpose, we present N3Sim, a simulation framework for diffusion-based molecular communication. N3Sim allows to simulate scenarios where transmitters encode the information by releasing molecules into the medium, thus varying their local concentration. N3Sim models the movement of these molecules according to Brownian dynamics, and it also takes into account their inertia and the interactions among them. Receivers decode the information by sensing the particle concentration in their neighborhood. The benefits of N3Sim are multiple: the validation of channel models for molecular communication and the evaluation of novel modulation schemes are just a few examples.

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  • A highly-accurate low-power CMOS potentiostat for implantable biosensors

     Razzaghpour, Milad; Rodriguez Duenas, Saul; Alarcon Cot, Eduardo Jose; Rusu, Ana
    IEEE Biomedical Circuits and Systems Conference (BioCAS)
    p. 5-8
    DOI: 10.1109/BioCAS.2011.6107713
    Presentation's date: 2011-11-11
    Presentation of work at congresses

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    Current-mirror-based potentiostats suffer from systematic and random errors causing offset, gain and linearity error in reading out the sensor data. In this work, a new potentiostat topology is proposed to eliminate the systematic error via an error-cancellation loop. The loop takes advantage of an error-tracking amplifier connected to a transimpedance amplifier with adjustable input common-mode voltage. Due to the enhanced loop gain, the potentiostat is able to accurately copy the sensor current which will then be converted into the proportional voltage. Additionally, a theoretical discussion of the proposed topology is given and a thorough study on the effect of random error sources is carried out. The potentiostat is designed and simulated in a 150nm CMOS process. The results verify a highly-linear highly-accurate performance in a low-noise condition, while consuming only 32 μW.

  • Implementación y primeros resultados de la asignatura de introducción a la ingeniería en los nuevos grados de la ETSETB-UPC

     Bragos Bardia, Ramon; Pegueroles Valles, Josep Rafel; Alarcon Cot, Eduardo Jose; Camps Carmona, Adriano Jose; Sarda Ferrer, Joan; Consolacion Segura, Carolina Maria; Mussons Selles, Jaume; Pons Peregort, Olga; Oliveras Verges, Albert; Garcia Hernandez, Miguel Jesus; Onrubia Ibañez, Raul; Sayrol Clols, Elisa
    Conferencia Internacional de Fomento e Innovación con Nuevas Tecnologías en la Docencia de la Ingeniería
    p. 263-266
    Presentation's date: 2011-05-05
    Presentation of work at congresses

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    En este trabajo se describe la asignatura "Introducción a la Ingeniería de las TIC" que, basándose en restricciones y especificaciones iniciales, ha sido concebida, diseñada e implementada en la ETSETB de la UPC. Es la primera de una serie de cuatro asignaturas de proyectos distribuidas a lo largo de los grados. Está organizada en tres itinerarios paralelos que cubren la visión de sistema TIC complejo, los conceptos básicos de economía, empresa y gestión de proyectos y la realización física de un proyecto. En los primeros 5 años este proyecto se lleva a cabo sobre la plataforma SeaPerch, un pequeño robot subacuático desarrollado en el MIT Sea Grant, sobre el que se diseñan y construyen sistemas de medida y comunicaciones. Después de probarla con grupos pequeños durante dos cuatrimestres, se acomete su explotación con una previsión de 250 estudiantes en el cuatrimestre de primavera de este año.

  • Continuous-time CMOS adaptive asynchronous sigma-delta modulator approximating low-fs low-inband-error on-chip wideband power amplifier

     Alarcon Cot, Eduardo Jose; Fernández, Diego; Garcia Tormo, Albert; Madrenas Boadas, Jordi; Poveda Lopez, Alberto
    IEEE International Symposium on Circuits and Systems
    p. 301-304
    DOI: 10.1109/ISCAS.2011.5937561
    Presentation's date: 2011-05-15
    Presentation of work at congresses

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    A mixed-signal continuous-time-processing standard CMOS implementation of an asynchronous sigma-delta modulator aimed to drive a switching amplifier operating as an on-chip wideband adaptive power supply is presented in this work. The paper first briefly discusses the fundamental limit tracking capabilities of a two-level switching signal to inband-error-free track a bandlimited signal with minimum average switching frequency. It is argued the adequacy of an adaptive asynchronous sigma-delta modulator (AAΣΔ) to approximate such fundamental characteristics. The second part of the paper presents mixed-signal design details of the various subcircuits implementing a CMOS low-power digitally-programmable AAΣΔ modulator, with 7 MHz average switching frequency operation and 1000 µm × 640 µm area occupancy.

  • Wireless nanosensor networks using graphene-based nano-antennas

     Abadal Cavalle, Sergi; Jornet, Josep Miquel; Llatser Marti, Ignacio; Cabellos Aparicio, Alberto; Alarcon Cot, Eduardo Jose; Akyildiz, Ian F.
    International Conference on GRAPHENE
    p. 1-2
    Presentation's date: 2011-04
    Presentation of work at congresses

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  • Bandwidth extension techniques for high-efficiency power amplifiers  Open access

     Garcia Tormo, Albert
    Department of Electronic Engineering, Universitat Politècnica de Catalunya
    Theses

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    Aquesta tesi tracta sobre amplificació de potència d'alt rendiment de senyals variables en el temps; concretament, tracta sobre conversió de potència eficient (amb mínimes pèrdues) de tensions DC continues en senyals de tensió no constants. Aquest tipus de conversió de potència està present en la majoria de dispositius electrònics d'ús quotidià, com ara telèfons mòbils i reproductors de música portàtils, així com també en dispositius d'alta potència com amplificadors d'àudio i estacions base de telefonia mòbil. Generalment l'energia està disponible en forma de tensió DC contínua (d'una bateria o d'una font d'alimentació). D'acord amb la informació a transmetre, aquesta energia s'ha de processar o transformar en un senyal variable en el temps de manera que, per exemple, es pugui convertir en àudio per un altaveu . La tendència de mercat és a reduir la mida i el pes dels dispositius electrònics i a oferir noves funcionalitats, incloent una llarga autonomia en dispositius alimentats per bateries. Millorar l'eficiència dels amplificadors de potència no només n'estendria l'autonomia, sinó que també permetria utilitzar dissipadors més petits i lleugers. Altres aplicacions com les d'alta potència o integrades també es beneficiarien de millores en l'eficiència dels amplificadors de potència. Els dispositius electrònics de processament de potència més eficients són els amplificadors commutats. Aquests utilitzen components reactius (bàsicament bobines i condensadors) per dur a terme un processament de potència idealment sense pèrdues, així com dispositius actius (transistors) controlats com interruptors (o bé tancats o bé oberts), per tal de controlar aquest procés. Tot i que es poden assolir eficiències molt altes amb amplificadors commutats, la precisió de seguiment pot no ser gaire bona. Es pot millorar la precisió de seguiment senzillament incrementant la freqüència de commutació (la freqüència a la qual es fan commutar els interruptors), tot i que, com que es requereix una certa quantitat d'energia per fer commutar cada interruptor (pèrdues de commutació), aquesta tècnica també deteriora l'eficiència de l'amplificador. Existeix doncs un comprimís entre la freqüència de commutació i la precisió de seguiment en els amplificadors commutats (compromís eficiència-distorsió). Els amplificadors commutats habitualment es dissenyen per treballar a una freqüència de commutació alta comparada amb l'amplada de banda que han de seguir. Mentre que amb aquesta estratègia de disseny (i tecnologia actual) es poden dissenyar amplificadors per seguir senyals de l'ordre de kHz, si s'aplica per seguir senyals de l'ordre de MHz, els amplificadors haurien de treballar a freqüències de commutació massa altes, inviables des del punt de vista de les pèrdues de commutació. Amb l'objectiu d'abordar el compromís entre distorsió i eficiència dels amplificadors commutats, aquesta tesi explora diferents tècniques per estendre l'amplada de banda relativa dels amplificadors commutats, és a dir, tècniques per reduir la relació entre la freqüència de commutació de l'amplificador i la seva amplada de banda de seguiment. Basant-se en una interpretació alternativa dels amplificadors commutats, com a procés de codificació i reconstrucció, les diferents tècniques d'extensió de banda que aquí s'exploren contemplen utilitzar modulacions alternatives, amplificació de potència multi-nivell, filtrat d'ordre elevat i polítiques de commutació millorades en els convertidors commutats. La caracterització de les prestacions en termes de freqüència de commutació, error de seguiment i robustesa davant no idealitats (incloent compatibilitat electromagnètica i acoblament entre canals) apunta la idoneïtat de l'amplificació de potència multi-nivell basada en moduladors asíncrons per dissenys que treballin a freqüències de commutació relativament baixes, és a dir, a freqüències de commutació comparables a l'amplada de banda del senyal a seguir i amplificar.

    This thesis is about power amplification of time-varying signals; more precisely, it is about efficient power conversion, i.e. with minimum losses, of DC constant voltages into non-constant voltage signals. This kind of power conversion is quite common in power-management circuits and electronics in general. It is present in most everyday use electronic devices, including mobile phones, portable audio players and routers, as well as in high-power devices such as audio amplifiers and wireless base stations. In most electronic devices, whether portable or not, the energy is available as DC constant voltage (typically from a battery or a power supply). According to the information to transmit, this energy must be processed or transformed into a time-varying analogue signal so that, for instance, it can be directly converted into audio by a speaker or radiated by an antenna. The market trend is to reduce the size and weight of electronic devices whilst offering new or enhanced functionalities, including long autonomy in battery-powered devices (mainly portable). Improving the efficiency of power amplifiers not only extends the autonomy, but also allows using smaller and lighter heatsinks. Other applications such as high-power or embedded would also benefit from efficiency improvements of switching amplifiers. The most efficient power-processing electronic devices are switching amplifiers. Switching amplifiers use reactive components (mainly inductors and capacitors) to perform an ideally lossless power processing, and active devices (transistors) driven as switches, either ON or OFF, to control this process. Whilst very high efficiencies can be achieved with switching amplifiers, their tracking fidelity may not be very high. The tracking fidelity can be improved by simply increasing the switching frequency (i.e. the frequency at which the active devices are driven), although, provided that a certain amount of energy is required to switch the state of each active device (switching losses), this technique also degrades the efficiency of the amplifiers. Therefore, there exists a trade-off between switching frequency and tracking fidelity in switching amplifiers (efficiency-distortion trade-off). Switching amplifiers are typically designed using a high switching frequency compared to the amplifier's tracking bandwidth. Whilst this design strategy leads to feasible designs for kHz-bandwidth applications (using state-of-the-art technology), when applied to MHz-bandwidth applications, it leads to designs operating at very high switching frequencies, unfeasible with regard to switching losses. With the scope of addressing the efficiency-distortion trade-off of switching amplifiers, this thesis explores different techniques to extend the relative bandwidth of switching amplifiers, i.e. techniques to reduce the ratio of the amplifier's switching frequency to the amplifier's tracking bandwidth. Based on an alternative interpretation of switching amplifiers, as an encoding-reconstruction process, the different bandwidth extension techniques consider using alternative modulations, multi-level power amplification, high-order filtering and enhanced switching policies in the switching converter. The performance characterisations in terms of switching frequency, tracking error and robustness against non-idealities (including electromagnetic compatibility and crosstalk) points out the suitability of multi-level power amplification based on asynchronous modulators for designs operating at relatively low switching frequencies, i.e. at switching frequencies in the same range than the bandwidth of the signal to track and power amplify.

  • A voltage-sensing circuit structure for a switching power converter and method for an enhanced fast-scale stability margin of a switching power converter

     Rodriguez Vilamitjana, Enric; El Aroudi, Abdelali; Alarcon Cot, Eduardo Jose
    Date of request: 2011-02-20
    Invention patent

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