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  • Microwave spectrometry for the evaluation of the structural integrity of metallic stents

     Arauz-Garofalo, Gianluca; López-Domínguez, Víctor; Hernández, Joan Manel; Rodríguez-Leor, Oriol; Bayes-Genis, Antoni; O'callaghan Castella, Juan Manuel; García-Santiago, Antoni; Tejada Palacios, Javier
    Medical physics
    Date of publication: 2014-04-01
    Journal article

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    PURPOSE: To assess the feasibility of a method based on microwave spectrometry to detect structural distortions of metallic stents in open air conditions and envisage the prospects of this approach toward possible medical applicability for the evaluation of implanted stents. METHODS: Microwave absorbance spectra between 2.0 and 18.0 GHz were acquired in open air for the characterization of a set of commercial stents using a specifically design setup. Rotating each sample over 360°, 2D absorbance diagrams were generated as a function of frequency and rotation angle. To check our approach for detecting changes in stent length (fracture) and diameter (recoil), two specific tests were performed in open air. Finally, with a few adjustments, this same system provides 2D absorbance diagrams of stents immersed in a water-based phantom, this time over a bandwidth ranging from 0.2 to 1.8 GHz. RESULTS: The authors show that metallic stents exhibit characteristic resonant frequencies in their microwave absorbance spectra in open air which depend on their length and, as a result, may reflect the occurrence of structural distortions. These resonances can be understood considering that such devices behave like dipole antennas in terms of microwave scattering. From fracture tests, the authors infer that microwave spectrometry provides signs of presence of Type I to Type IV stent fractures and allows in particular a quantitative evaluation of Type III and Type IV fractures. Recoil tests show that microwave spectrometry seems able to provide some quantitative assessment of diametrical shrinkage, but only if it involves longitudinal shortening. Finally, the authors observe that the resonant frequencies of stents placed inside the phantom shift down with respect to the corresponding open air frequencies, as it should be expected considering the increase of dielectric permittivity from air to water. CONCLUSIONS: The evaluation of stent resonant frequencies provided by microwave spectrometry allows detection and some quantitative assessment of stent fracture and recoil in open air conditions. Resonances of stents immersed in water can be also detected and their characteristic frequencies are in good agreement with theoretical estimates. Although these are promising results, further verification in a more relevant phantom is required in order to foresee the real potential of this approach.

    PURPOSE: To assess the feasibility of a method based on microwave spectrometry to detect structural distortions of metallic stents in open air conditions and envisage the prospects of this approach toward possible medical applicability for the evaluation of implanted stents. METHODS: Microwave absorbance spectra between 2.0 and 18.0 GHz were acquired in open air for the characterization of a set of commercial stents using a specifically design setup. Rotating each sample over 360°, 2D absorbance diagrams were generated as a function of frequency and rotation angle. To check our approach for detecting changes in stent length (fracture) and diameter (recoil), two specific tests were performed in open air. Finally, with a few adjustments, this same system provides 2D absorbance diagrams of stents immersed in a water-based phantom, this time over a bandwidth ranging from 0.2 to 1.8 GHz. RESULTS: The authors show that metallic stents exhibit characteristic resonant frequencies in their microwave absorbance spectra in open air which depend on their length and, as a result, may reflect the occurrence of structural distortions. These resonances can be understood considering that such devices behave like dipole antennas in terms of microwave scattering. From fracture tests, the authors infer that microwave spectrometry provides signs of presence of Type I to Type IV stent fractures and allows in particular a quantitative evaluation of Type III and Type IV fractures. Recoil tests show that microwave spectrometry seems able to provide some quantitative assessment of diametrical shrinkage, but only if it involves longitudinal shortening. Finally, the authors observe that the resonant frequencies of stents placed inside the phantom shift down with respect to the corresponding open air frequencies, as it should be expected considering the increase of dielectric permittivity from air to water. CONCLUSIONS: The evaluation of stent resonant frequencies provided by microwave spectrometry allows detection and some quantitative assessment of stent fracture and recoil in open air conditions. Resonances of stents immersed in water can be also detected and their characteristic frequencies are in good agreement with theoretical estimates. Although these are promising results, further verification in a more relevant phantom is required in order to foresee the real potential of this approach.

  • Microwave spectrometry for the assessment of the structural integrity and restenosis degree of coronary stents

     Arauz-Garofalo, Gianluca; López-Domínguez, Víctor; García-Santiago, Antoni; Tejada Palacios, Javier; O'callaghan Castella, Juan Manuel; Rodríguez-Leor, Oriol; Bayes-Genis, Antoni
    APS March Meeting
    Presentation's date: 2013-03-20
    Presentation of work at congresses

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    Cardiovascular disease is the main cause of death worldwide. Coronary stents are one of the most important improvements to reduce deaths from cardiovascular disorders. Stents are prosthetic tube-shaped devices which are used to rehabilitate obstructed arteries. Despite their obvious advantages, reocclusion occurs in some cases arising from restenosis or structural distortions, so stented patients require chronic monitoring (involving invasive or ionizing procedures). We study microwave scattering spectra (between 2.0 - 18.0 GHz) of metallic stents in open air, showing that they behave like dipole antennas in terms of microwave scattering. They exhibit characteristic resonant frequencies in their microwave absorbance spectra that are univocally related to their length and diameter. This fact allows one to detect stent fractures or collapses. We also investigate the ``dielectric shift'' in the frequency of the resonances mentioned above due to the presence of different fluids along the stent lumen. This shift could give us information about the restenosis degree of implanted stents.

  • Microwave spectrometry for the evaluation of the structural integrity and the restenosis degree of coronary stents

     Arauz-Garofalo, Gianluca; Rodríguez-Leor, Oriol; Bayes-Genis, Antoni; O'callaghan Castella, Juan Manuel; García-Santiago, Antoni; Tejada Palacios, Javier
    Reunión Bienal de la Real Sociedad Española de Física
    Presentation's date: 2013-07-18
    Presentation of work at congresses

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  • Óxidos y estructuras híbridas de respuesta multifuncional

     O'callaghan Castella, Juan Manuel; Mateu Mateu, Jordi
    Participation in a competitive project

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  • A Large-Signal Model of Ferroelectric Thin-Film Transmission Lines

     Rocas Cantenys, Eduard; Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; Orloff, Nathan D.; O'callaghan Castella, Juan Manuel; Booth, James C.
    IEEE transactions on microwave theory and techniques
    Date of publication: 2011-12
    Journal article

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  • First-order elastic nonlinearities of bulk acoustic wave resonators

     Collado Gomez, Juan Carlos; Padilla Díaz, Alberto; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel; Orloff, Nathan D.; Booth, James C.; Iborra, Enrique; Aigner, Robert; Rocas Cantenys, Eduard
    IEEE transactions on microwave theory and techniques
    Date of publication: 2011-05
    Journal article

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    Passive intermodulation due to self-heating in printed transmission lines  Open access

     Collado Gomez, Juan Carlos; Orloff, Nathan D.; Mateu Mateu, Jordi; Padilla Díaz, Alberto; O'callaghan Castella, Juan Manuel; Booth, James C.; Rocas Cantenys, Eduard
    IEEE transactions on microwave theory and techniques
    Date of publication: 2011
    Journal article

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  • Superconducting Multiplexer Filter Bank for a Frequency-Selective Power Limiter

     Padilla Díaz, Alberto; Mateu Mateu, Jordi; Orloff, Nathan D.; O'callaghan Castella, Juan Manuel; Collado Gomez, Juan Carlos; Booth, James C.; Rocas Cantenys, Eduard
    IEEE transactions on applied superconductivity
    Date of publication: 2011-06
    Journal article

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  • Research & Development of a Simulator for Moving Target Indicator System

     Makhoul Varona, Eduardo; Rius Casals, Juan-manuel; Aguasca Sole, Alberto; O'callaghan Castella, Juan Manuel; Broquetas Ibars, Antoni
    Participation in a competitive project

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  • Design and synthesis of a new class of receiver filters

     Mateu Mateu, Jordi; Collado Gomez, Juan Carlos; Padilla Díaz, Alberto; Rius Casals, Juan-manuel; O'callaghan Castella, Juan Manuel; Cuñado, O; Torra, J; Mingot, S; Ernst, Cristoph
    ESA Techno/Innovation Days
    Presentation's date: 2011-11-23
    Presentation of work at congresses

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  • Mixed integration of CDIO skills into telecommunication engineering curricula

     Sayrol Clols, Elisa; Bragos Bardia, Ramon; Alarcon Cot, Eduardo Jose; Cabrera Bean, Margarita Asuncion; Calveras Auge, Ana M.; Comellas Colome, Jaume; O'callaghan Castella, Juan Manuel; Pegueroles Valles, Josep Rafel; Pla, E; Prat Viñas, Luis; Saez Moreno, German; Sardà ., J; Tallon Montoro, Carme
    Elektronika ir elektrotechnika
    Date of publication: 2010
    Journal article

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  • New European Watcher

     Rius Casals, Juan-manuel; O'callaghan Castella, Juan Manuel; Makhoul Varona, Eduardo; Broquetas Ibars, Antoni
    Participation in a competitive project

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    Synthesis of 4th order lossy filters with uniform Q distribution  Open access

     Mateu Mateu, Jordi; Padilla Díaz, Alberto; Collado Gomez, Juan Carlos; Martínez-Mendoza, Mónica; Ernst, Cristoph; O'callaghan Castella, Juan Manuel; Rocas Cantenys, Eduard
    IEEE International Microwave Symposium
    Presentation's date: 2010-05
    Presentation of work at congresses

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  • Lossy filter synthesis of L-band planar filters using novel software

     Padilla Díaz, Alberto; Mateu Mateu, Jordi; Collado Gomez, Juan Carlos; Ernst, Cristoph; Rius Casals, Juan-manuel; Tamayo Palau, Jose Maria; O'callaghan Castella, Juan Manuel; Rocas Cantenys, Eduard
    Microwave Technology and Techniques Workshop
    Presentation's date: 2010-05-12
    Presentation of work at congresses

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    Lossy synthesis techniques are used to synthesize high performance filters using resonators with a finite Q. With these techniques a transmission response of a lossless filter with lowest possible roll-off is obtained, except for an overall constant additional insertion loss. The out-of band performance is not affected. These types of filters are useful in receiver architectures where the filter can be placed following an amplifying stage and some increase in insertion loss can be tolerated without affecting the noise figure. Due to the lower resonator Q that can be employed, low cost and compact filters (such as microstrip filters) can be realized. Hence this work presents the synthesis and design of two planar lossy filters. Both filters have been designed using microstrip technology, with center frequencies of 1 GHz and 1.6 GHz, and bandwidth of 36 MHz and 80 MHz, respectively. Both filters exhibit a flat in-band response with an insertion loss of 10 dB and 7.5 dB, respectively. The topologies obtained from the synthesis result in a 4th and a 6th order filters at 1 GHz and 1.6 GHz, respectively. Both topologies present a uniform Q distribution throughout the networks, this is all the resonators of the filter are equal to 200 and 290, respectively. In contrast with conventional filter networks, where all the couplings are reactive, lossy filters require some of the couplings to be resistive. The main difference between the two filters presented is the type of frequency response. While the filter at 1 GHz synthesizes a response with a stopband 10 dB return loss, the filter at 1.6 GHz synthesizes a purely reflective response in the stopband. The presentation will also show details of the software package that has been written to synthesize filters following various forms of pre-distortion, classical (no-loss considered in the synthesis) and lossy filter synthesis. This software obtains the coupling matrix of several network topologies for a given response and allows performing rotations on them to find the desired topology. Additionally, the software allows to evaluate the effect of loss in the networks resulting from the synthesis, even in those cases where the synthesis results in an ideal lossless network (i.e., classical and pre-distortion synthesis).

  • Application of lossy filter synthesis to a C-band cavity filter and its prospect for use in IMUX

     O'callaghan Castella, Juan Manuel; Padilla Díaz, Alberto; Mateu Mateu, Jordi; Rius Casals, Juan-manuel; Tamayo Palau, Jose Maria; Collado Gomez, Juan Carlos; Rocas Cantenys, Eduard
    Microwave Technology and Techniques Workshop
    Presentation's date: 2010-05-12
    Presentation of work at congresses

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  • Supercoducting multiplexer filter bank for a frequency selective power limiter

     Mateu Mateu, Jordi; Padilla Díaz, Alberto; O'callaghan Castella, Juan Manuel; Collado Gomez, Juan Carlos; Rocas Cantenys, Eduard
    Applied Superconductivity Conference
    Presentation's date: 2010-08
    Presentation of work at congresses

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  • Proceso de inversión de competencias genéricas en los nuevos planes de estudios de grado de la ETSETB de acuerdo con el modelo CDIO

     Bragos Bardia, Ramon; Alarcon Cot, Eduardo Jose; Cabrera Bean, Margarita Asuncion; Calveras Auge, Ana M.; Comellas Colome, Jaume; O'callaghan Castella, Juan Manuel; Pegueroles Valles, Josep Rafel; Prat Viñas, Luis; Saez Moreno, German; Sardà ., J; Sayrol Clols, Elisa
    Congreso de Tecnologías Aplicadas a la Enseñanza de la Electrónica
    Presentation's date: 2010-04-13
    Presentation of work at congresses

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    Comparison of lossy filters and predistorted filters using novel software  Open access

     Padilla Díaz, Alberto; Mateu Mateu, Jordi; Collado Gomez, Juan Carlos; Ernst, Cristoph; Rius Casals, Juan-manuel; Tamayo Palau, Jose Maria; O'callaghan Castella, Juan Manuel
    IEEE International Microwave Symposium
    Presentation's date: 2010-05
    Presentation of work at congresses

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    Nonlinear distributed model for bulk acoustic wave resonators  Open access

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; Padilla Díaz, Alberto; O'callaghan Castella, Juan Manuel; Rocas Cantenys, Eduard
    IEEE transactions on microwave theory and techniques
    Date of publication: 2009-12
    Journal article

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    This work expands the model proposed by Krimtholz, Leedom, and Matthaei (KLM) model to account for the nonlinear effects occurring in acoustic devices due to the nonlinear stiffened elasticity.We show that a nonlinear distributed capacitance in the acoustic transmission line of the KLM model can account for the distributed nature of the nonlinear effects. Specifically, we use the nonlinear telegrapher’s equation to find closed-form equations for intermodulation distortion and harmonic generation. We confirm the validity of these equations by comparing their results with those provided by aKLMequivalent circuit in which the nonlinear transmission line is implemented by cascading many L-C cells having a voltage-dependent capacitance. To further confirm the model, we show measured nonlinear effects in a thin film bulk acoustic resonator in close agreement with the equivalent circuit simulations.

  • Third-order intermodulation distortion and harmonic generation in mismatched weakly nonlinear transmission lines

     Mateu Mateu, Jordi; Collado Gomez, Juan Carlos; Orloff, N; Booth, James C.; Rocas, E; O'callaghan Castella, Juan Manuel
    IEEE transactions on microwave theory and techniques
    Date of publication: 2009-01
    Journal article

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  • Guia per a l'avaluació de competències als treballs de final de grau i de màster a les enginyeries

     Valderrama Vallés, Elena; Bisbal Riera, Jesús; Carrera Muyo, Julián; Castells Piqué, Francesc; Cores Prado, Fernando; Garcia Almiñana, Jordi; Giné de Sola, Francesc; Jiménez Esteller, Laureano; Mans Teixidó, Claudi; Margalef Burrull, Tomàs; Moreno Bilbao, M. Asuncion; O'callaghan Castella, Juan Manuel; Peig Olivé, Enric; Pérez Cañestro, Julio; Pons Aróztegui, Jordi; Renau Folch, Josep; Rullán Ayza, Mercè; Sanchez Carracedo, Fermin; Seco Granados, Gonzalo; Sorribes Gomis, Joan; Tejero Salvador, Javier; Vilanova Arbós, Ramón; Lozano Costa, Verónica
    Date of publication: 2009
    Book

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  • Superconducting filters and passive components

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel; Mareu, J
    Date of publication: 2009-08-31
    Book chapter

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  • MEDIDAS DE EFECTOS DE SINTONIZABILIDAD EN MATERIALES MULTIFERROICOS

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel
    Participation in a competitive project

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  • Dispositivo y filtro de onda acústica

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel; Padilla Díaz, Alberto; Rocas Cantenys, Eduard
    Date of request: 2009-07-08
    Invention patent

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    Dispositivo y filtro de onda acústica.

    El dispositivo comprende dos o más electrodos (1, 2), una capa activa piezoeléctrica (3) y unos medios de compensación de señales que comprenden como mínimo una capa compensatoria dieléctrica (4) configurada y ubicada para compensan señales espurias generadas, al aplicar una señal de entrada a dichos electrodos (1, 2), por unas no linealidades intrínsecas sustancialmente independientes de la temperatura, inherentes a las propiedades de elasticidad no lineales del material de al menos dicha capa activa (3).

    Para un ejemplo de realización los medios de compensación comprenden una fuente de tensión continua (Vdc) en conexión eléctrica con unas capas de alta conductividad (1, 2) entre las que se encuentra la capa compensatoria dieléctrica (4), para aplicar una tensión continua que varíe sus propiedades de elasticidad no lineales.

    El filtro comprende uno o más dispositivos como el propuesto por la invención.

  • Third order Intermodulation distortion in film bulk acoustic resonator at resonance and antiresonance

     Rocas, E; Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; Campanella, H; O'callaghan Castella, Juan Manuel
    IEEE International Microwave Symposium
    Presentation of work at congresses

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  • A Cavity measurement setup for determining IMD properties of top and bottom sides of HTS films

     Diaz, R; Mateu Mateu, Jordi; Collado Gomez, Juan Carlos; O'callaghan Castella, Juan Manuel
    2008 IEEE Applied Superconductivity Conference
    Presentation of work at congresses

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  • Nonlinear distributed model for IMD prediction in BAW resonators

     Rocas, E; Collado Gomez, Juan Carlos; Padilla, A; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel
    2008 IEEE International Ultrasonics Symposium
    Presentation of work at congresses

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  • Modeling superconducting transmission line bends and their impact on nonlinear effects

     Mateu Mateu, Jordi; Collado Gomez, Juan Carlos; O'callaghan Castella, Juan Manuel
    IEEE transactions on microwave theory and techniques
    Date of publication: 2007-05
    Journal article

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  • Intermodulation distortion in coupled-resonator filters with nonuniformly distributed nonlinear properties - use in HTS IMD compensation

     Mateu Mateu, Jordi; Booth, James C.; Collado Gomez, Juan Carlos; O'callaghan Castella, Juan Manuel
    IEEE transactions on microwave theory and techniques
    Date of publication: 2007-04
    Journal article

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  • Detuning and saturation of superconducting devices : formulation and measurements

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; Booth, James C.; O'callaghan Castella, Juan Manuel
    IEEE MTT-S International Microwave Symposium
    Presentation of work at congresses

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    Miniaturization of superconducting filters using Hilbert fractal curves  Open access

     Barra, Mario; Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel
    IEEE transactions on applied superconductivity
    Date of publication: 2007-05
    Journal article

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    This work presents novel compact high-temperature superconductor microstrip resonators and filters based on the Hilbert space-filling fractal curve. Several Hilbert resonator configurations have been assessed by using a full-wave electromagnetic simulator and their miniaturization performance has been investigated, emphasizing the parameters which allow obtaining good tradeoff between compact size and losses. These resonators have proved to be useful for filter design. A four-pole 2.45-GHz quasi-elliptic filter and a four-pole 1.9-GHz Chebyshev filter have been realized by patterning 10 mm/spl times/10 mm Y/sub 2/Ba/sub 3/Cu/sub 7-/spl delta//O thin films on MgO substrates. Insertion losses of the order of 0.2 dB have been measured, showing good agreement with the simulations.

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    Analysis and simulation of distributed nonlinearities in ferroelectrics and superconductors for microwave applications  Open access

     Seron, David; Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel
    IEEE transactions on microwave theory and techniques
    Date of publication: 2006-03
    Journal article

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    This paper gives closed-form equations for the intermodulation and third harmonic signals generated in a nonlinear transmission line with distributed quadratic nonlinearities in the conductor and dielectric. Although the formulation developed is general, it is intended to be used in planar devices combining high-temperature superconductor (HTS) and oxide ferroelectrics. The analysis in this paper shows that the intermodulation and third harmonic signals produced by an HTS tend to cancel those of a ferroelectric, and that full cancellation is theoretically possible. This opens the way for using HTS/ferroelectric multilayers, not (only) for their tunable or phase-shifting properties, but for highly linear spurious-free planar HTS devices.

  • Unified description of nonlinear effects in high temperature superconductor microwave devices

     Booth, James C.; Leong, K; Schima, S A; Collado Gomez, Juan Carlos; O'callaghan Castella, Juan Manuel; Mateu Mateu, Jordi
    Journal of superconductivity and novel magnetism
    Date of publication: 2006-11
    Journal article

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  • Introduction to special issue of the proceedings of the 8th Symposium on High Temperature Superconductors in High Frequency Fields

     Kokabi, H; O'callaghan Castella, Juan Manuel
    Journal of superconductivity and novel magnetism
    Date of publication: 2006-11
    Journal article

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  • Measurements and analysis of microwave nonlinearities in ferroelectric thin film transmission lines

     Mateu Mateu, Jordi; Booth, James C.; Schima, S A; Collado Gomez, Juan Carlos; Seron, David; O'callaghan Castella, Juan Manuel
    IEEE International Microwave Symposium
    Presentation of work at congresses

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  • Miniaturización y mejora de cabeceras de radiofrecuencia mediante el uso de nuevos materiales y metamateriales

     Collado Gomez, Juan Carlos; Heldring, Alexander; Santos Blanco, María Concepción; O'callaghan Castella, Juan Manuel; Ubeda Farre, Eduardo; González Arbesú, José María; Mateu Mateu, Jordi
    Participation in a competitive project

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  • Analitzador d'espectres; tarja d'adquisició

     O'callaghan Castella, Juan Manuel
    Participation in a competitive project

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  • Intermodulation distortion in coupled-resonator filters with non-uniform distributed nonlinear properties : use in HTS IMD compensation

     Mateu Mateu, Jordi; Booth, James C.; Collado Gomez, Juan Carlos; Seron, David; O'callaghan Castella, Juan Manuel
    Symposium on High Temperature Supercondutors High Frequency Field 2006
    Presentation of work at congresses

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  • Relating experiments and models in nonlinear HTS transmission lines

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; Seron, David; O`Callaghan, J M; O'callaghan Castella, Juan Manuel
    Applied Superconductivity Conference 2006
    Presentation of work at congresses

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  • A novel use of oxide ferroelectrics : compensation microwave nonlinearities in HTS planar devices

     Seron, David; Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; O`Callaghan, J M; O'callaghan Castella, Juan Manuel
    Applied Superconductivity Conference 2006
    Presentation of work at congresses

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  • High Tc Superconducting filters with ferroelectric inserted segments for mitigation of nonlinear effects

     Mateu Mateu, Jordi; Booth, James C.; Collado Gomez, Juan Carlos; Seron, David; O'callaghan Castella, Juan Manuel
    International Workshop on Microwave Filters
    Presentation of work at congresses

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    General equations for the induced phase shift in resonant electro-optic modulators  Open access

     Collado Gomez, Juan Carlos; Menéndez, O; Santos Blanco, María Concepción; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel
    IEEE photonics technology letters
    Date of publication: 2005-02
    Journal article

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    We derive general equations to calculate the electrooptically induced optical phase shift in resonantly enhanced modulators. The equations are useful in designing modulator electrodes with optimal length and optimal mismatch between electrical and optical velocities. We demonstrate the existence of an optimal velocity mismatch depending on the resonant mode used.

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    Performance projection of electro-optical modulators for radio-over-fiber in 2 GHz cryogenic front-end receivers  Open access

     Menéndez, O; Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; Santos Blanco, María Concepción; O'callaghan Castella, Juan Manuel
    IEEE transactions on applied superconductivity
    Date of publication: 2005-06
    Journal article

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    We present the design of a Y-Ba-Cu-O on LiNbO/sub 3/ cryogenic electro-optical modulator for analog 2 GHz applications. A resonant configuration of coplanar electrodes is considered, showing improvements with respect to both resonant Au electrodes and to traveling-wave electrodes, even beyond the traveling-wave theoretical maximum performance limit. The optimized layout is presented featuring a reduced length of 8.26 mm.

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    Analysis and simulation of the effects of distributed nonlinearities in microwave superconducting devices  Open access

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel
    IEEE transactions on applied superconductivity
    Date of publication: 2005-03
    Journal article

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    This paper presents a comprehensive study of microwave nonlinearities in superconductors, with an emphasis on intermodulation distortion and third-harmonic generation. It contains the analysis of various resonant and nonresonant test devices and its validation using numerical simulations based on harmonic balance (HB). The HB simulations made on test devices show that the closed-form equations for intermodulation and third-harmonic generation are only valid at low power levels. The paper also contains examples of application of HB to illustrate that this technique is useful to simulate superconductive devices other than simple test devices, and that the validity of the simulations is not restricted to low drive power levels. Most of the analyses and simulations of this paper are based on electrical parameters that describe the nonlinearities in the superconducting material. These parameters are compatible with many existing models of microwave nonlinearities in superconductors. We discuss the particulars on how to relate these electrical parameters with one of the existing models that postulates that the nonlinear effects are due to a dependence of the penetration depth on the current density in the superconductor.

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    Nonlinear distortion in a 8-pole quasi-elliptic bandpass HTS filter for CDMA system  Open access

     Collado Gomez, Juan Carlos; Mateu Mateu, Jordi; Menéndez, O; O'callaghan Castella, Juan Manuel
    IEEE transactions on applied superconductivity
    Date of publication: 2005-06
    Journal article

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    High Temperature Superconductor materials are known to produce intermodulation and other nonlinear effects which may restrict their use in wireless communication systems. Quantifying this degradation is crucial in determining if the use of HTS filters in the receiver is beneficial. In this work we use an approach for representing the HTS filter nonlinear equivalent circuit and simulating its performance. We have tested the approach on a planar, 8-pole quasielliptic (QE) filter, showing agreement between simulations and measurements of intermodulation products (IMD). The nonlinear equivalent circuit is then used to predict the nonlinear behavior of the filter and its effects on system parameters when it is subject to broadband signals like those used in wireless communication systems.

  • Nonlinear model of coupled superconducting lines

     Mateu Mateu, Jordi; Collado Gomez, Juan Carlos; O'callaghan Castella, Juan Manuel
    IEEE transactions on applied superconductivity
    Date of publication: 2005-06
    Journal article

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  • Lineas de transmisión con materiales HTS/ferroelétcricos para sistemas de comunicaciones avanzados (MAT2005-05656-C04-03)

     O'callaghan Castella, Juan Manuel; Collado Gomez, Juan Carlos; Santos Blanco, María Concepción
    Participation in a competitive project

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  • Compact duplexer with miniaturized dual loop resonator

     Collado Gomez, Juan Carlos; Pozo, J; Mateu Mateu, Jordi; O'callaghan Castella, Juan Manuel
    35th European Microwave Conference (EuMC-2005)
    Presentation of work at congresses

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  • Superconductor HTS applications in communication systems

     O'callaghan Castella, Juan Manuel
    International Microwave and Optoelectronics Conference (SBMO / IEEE MTT-S)
    Presentation's date: 2005-07-25
    Presentation of work at congresses

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  • Pre-fractal antennas and resonators: Miniaturization, efficiency and bandwidth limitations

     Rius Casals, Juan-manuel; González Arbesú, José María; Collado Gomez, Juan Carlos; Romeu Robert, Jordi; O'callaghan Castella, Juan Manuel; Mosig, J R; Cardama Aznar, Angel
    Fractals in Engineering V
    Presentation of work at congresses

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