Articles de revista
http://hdl.handle.net/2117/653
2016-05-04T13:42:10ZA General approach for the calculation of intermodulation distortion in cavities with superconducting endplates
http://hdl.handle.net/2117/86367
A General approach for the calculation of intermodulation distortion in cavities with superconducting endplates
Mateu Mateu, Jordi; Collado Gómez, Juan Carlos; Menéndez, O; O'Callaghan Castellà, Juan Manuel
We report on a general procedure to calculate intermodulation distortion in cavities with superconducting endplates that is applicable to the dielectric-loaded cavities currently used for measurement of surface resistance in high-temperature superconductors. The procedure would enable the use such cavities for intermodulation characterization of unpatterned superconducting films, and would remove the uncertainty of measuring intermodulation on patterned devices, in which the effect of patterning damage might influence the outcome of the measurements. We have verified the calculation method by combining superconducting and copper endplates in a rutile-loaded cavity
2016-04-28T12:02:43ZMateu Mateu, JordiCollado Gómez, Juan CarlosMenéndez, OO'Callaghan Castellà, Juan ManuelWe report on a general procedure to calculate intermodulation distortion in cavities with superconducting endplates that is applicable to the dielectric-loaded cavities currently used for measurement of surface resistance in high-temperature superconductors. The procedure would enable the use such cavities for intermodulation characterization of unpatterned superconducting films, and would remove the uncertainty of measuring intermodulation on patterned devices, in which the effect of patterning damage might influence the outcome of the measurements. We have verified the calculation method by combining superconducting and copper endplates in a rutile-loaded cavityReduced microwave losses YBa2Cu3O7-d thin films on electro-optic LiNbO3 crystals
http://hdl.handle.net/2117/86351
Reduced microwave losses YBa2Cu3O7-d thin films on electro-optic LiNbO3 crystals
Fàbrega Sanchez, Lourdes; Rubi, R; Fontcuberta, J; Sanchez, F; Ferrater Lambarri, Carlos; Garcia-Cuenca, M V; Varela, M; Collado Gómez, Juan Carlos; Mateu Mateu, Jordi; Menéndez, O; O'Callaghan Castellà, Juan Manuel
2016-04-28T10:44:36ZFàbrega Sanchez, LourdesRubi, RFontcuberta, JSanchez, FFerrater Lambarri, CarlosGarcia-Cuenca, M VVarela, MCollado Gómez, Juan CarlosMateu Mateu, JordiMenéndez, OO'Callaghan Castellà, Juan ManuelNonlinear RF spurious in a cylindrical cavity with superconducting endplates
http://hdl.handle.net/2117/86344
Nonlinear RF spurious in a cylindrical cavity with superconducting endplates
Mateu Mateu, Jordi; Collado Gómez, Juan Carlos; Shaw, T J; O'Callaghan Castellà, Juan Manuel
We have developed a method to calculate the distribution of fundamental and spurious fields in a metallic cylindrical cavity with superconducting endplates in which signals at two different frequencies are injected. The nonlinearity in the superconductor produces the typical intermodulation effects if the frequencies of the injected signals are sufficiently close to each other and near a resonant mode. Our method uses harmonic balance to match the fields in the cavity with the currents on the endplates. The method can be used for a variety of nonlinear models of the superconducting endplate, and could be the base for a nondestructive procedure to extract the nonlinear parameters of an HTS sample from RF measurements. Our analysis is restricted to the TE011 mode, but the method can be applied to any propagating mode in the cylindrical cavity. Closed-form equations for the case of square-law nonlinearities in the superconductor are derived and used to check the validity of the harmonic balance calculation.
2016-04-28T10:33:28ZMateu Mateu, JordiCollado Gómez, Juan CarlosShaw, T JO'Callaghan Castellà, Juan ManuelWe have developed a method to calculate the distribution of fundamental and spurious fields in a metallic cylindrical cavity with superconducting endplates in which signals at two different frequencies are injected. The nonlinearity in the superconductor produces the typical intermodulation effects if the frequencies of the injected signals are sufficiently close to each other and near a resonant mode. Our method uses harmonic balance to match the fields in the cavity with the currents on the endplates. The method can be used for a variety of nonlinear models of the superconducting endplate, and could be the base for a nondestructive procedure to extract the nonlinear parameters of an HTS sample from RF measurements. Our analysis is restricted to the TE011 mode, but the method can be applied to any propagating mode in the cylindrical cavity. Closed-form equations for the case of square-law nonlinearities in the superconductor are derived and used to check the validity of the harmonic balance calculation.HTS nonlinearities in microwave disk resonators
http://hdl.handle.net/2117/86338
HTS nonlinearities in microwave disk resonators
Collado Gómez, Juan Carlos; Mateu Mateu, Jordi; Shaw, T J; O'Callaghan Castellà, Juan Manuel
This article describes a procedure for the calculation of the intermodulation behavior of the TM010 mode in high temperature superconducting (HTS) disk resonators from a description of the local HTS nonlinearities. Successful cross-checks are performed by comparing the theoretical results with experimental measurements and simulations based on the multiport harmonic balance algorithm for a specific model of HTS nonlinearity. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated and compared to theoretical predictions.
2016-04-28T10:23:28ZCollado Gómez, Juan CarlosMateu Mateu, JordiShaw, T JO'Callaghan Castellà, Juan ManuelThis article describes a procedure for the calculation of the intermodulation behavior of the TM010 mode in high temperature superconducting (HTS) disk resonators from a description of the local HTS nonlinearities. Successful cross-checks are performed by comparing the theoretical results with experimental measurements and simulations based on the multiport harmonic balance algorithm for a specific model of HTS nonlinearity. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated and compared to theoretical predictions.Nonlinear simulation and characterization of devices with HTS transmission lines using harmonic balance algorithm
http://hdl.handle.net/2117/86335
Nonlinear simulation and characterization of devices with HTS transmission lines using harmonic balance algorithm
Collado Gómez, Juan Carlos; Mateu Mateu, Jordi; O'Callaghan Castellà, Juan Manuel
This work presents the use of Harmonic Balance to simulate the nonlinear behavior of HTS transmission lines. Good agreement with theoretical cross-checks is found. We also show the use of this algorithm to fit the model of HTS lines from experimental measurements. We illustrate this by fitting several types of experimental data, and discuss how to avoid ambiguity in this fitting
2016-04-28T10:15:38ZCollado Gómez, Juan CarlosMateu Mateu, JordiO'Callaghan Castellà, Juan ManuelThis work presents the use of Harmonic Balance to simulate the nonlinear behavior of HTS transmission lines. Good agreement with theoretical cross-checks is found. We also show the use of this algorithm to fit the model of HTS lines from experimental measurements. We illustrate this by fitting several types of experimental data, and discuss how to avoid ambiguity in this fittingGeneral electromagnetic simulation tool to predict the microwave nonlinear response of planar, arbitrarily-shaped HTS structures
http://hdl.handle.net/2117/86327
General electromagnetic simulation tool to predict the microwave nonlinear response of planar, arbitrarily-shaped HTS structures
Parrón Granados, Josep; Collado Gómez, Juan Carlos; Mateu Mateu, Jordi; Rius Casals, Juan Manuel; Duffo Ubeda, Núria; O'Callaghan Castellà, Juan Manuel
This work describes a simulation tool being developed at UPC to predict the microwave nonlinear behavior of planar superconducting structures with very few restrictions on the geometry of the planar layout. The software is intended to be applicable to most structures used in planar HTS circuits, including line, patch, and quasi-lumped microstrip resonators. The tool combines Method of Moments (MoM) algorithms for general electromagnetic simulation with Harmonic Balance algorithms to take into account the nonlinearities in the HTS material. The Method of Moments code is based on discretization of the Electric Field Integral Equation in Rao, Wilton and Glisson Basis Functions. The multilayer dyadic Green's function is used with Sommerfeld integral formulation. The Harmonic Balance algorithm has been adapted to this application where the nonlinearity is distributed and where compatibility with the MoM algorithm is required. Tests of the algorithm in TM010 disk resonators agree with closed-form equations for both the fundamental and third-order intermodulation currents. Simulations of hairpin resonators show good qualitative agreement with previously published results, but it is found that a finer meshing would be necessary to get correct quantitative results. Possible improvements are suggested
2016-04-28T09:48:24ZParrón Granados, JosepCollado Gómez, Juan CarlosMateu Mateu, JordiRius Casals, Juan ManuelDuffo Ubeda, NúriaO'Callaghan Castellà, Juan ManuelThis work describes a simulation tool being developed at UPC to predict the microwave nonlinear behavior of planar superconducting structures with very few restrictions on the geometry of the planar layout. The software is intended to be applicable to most structures used in planar HTS circuits, including line, patch, and quasi-lumped microstrip resonators. The tool combines Method of Moments (MoM) algorithms for general electromagnetic simulation with Harmonic Balance algorithms to take into account the nonlinearities in the HTS material. The Method of Moments code is based on discretization of the Electric Field Integral Equation in Rao, Wilton and Glisson Basis Functions. The multilayer dyadic Green's function is used with Sommerfeld integral formulation. The Harmonic Balance algorithm has been adapted to this application where the nonlinearity is distributed and where compatibility with the MoM algorithm is required. Tests of the algorithm in TM010 disk resonators agree with closed-form equations for both the fundamental and third-order intermodulation currents. Simulations of hairpin resonators show good qualitative agreement with previously published results, but it is found that a finer meshing would be necessary to get correct quantitative results. Possible improvements are suggestedNonlinear Analysis of Disk Resonators: Application to Material Characterization and Filter Design
http://hdl.handle.net/2117/86325
Nonlinear Analysis of Disk Resonators: Application to Material Characterization and Filter Design
Mateu Llevadot, Jordi; O'Callaghan Castellà, Juan Manuel
A procedure for the numerical prediction of the microwave nonlinear behavior (intermodulation products, degradation of quality factors, etc.) of TM010 disk resonators has been developed. The procedure is based on relating a very general description of HTS nonlinearities with the circuit elements of a nonlinear radial transmission line. This radial transmission line is then analyzed using the harmonic balance algorithm. Successful cross-checks are performed by comparing simulations with theoretical results obtained for a specific model of HTS nonlinearity. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated as well as its use for simulating filters with several inter-coupled disks
2016-04-28T09:35:13ZMateu Llevadot, JordiO'Callaghan Castellà, Juan ManuelA procedure for the numerical prediction of the microwave nonlinear behavior (intermodulation products, degradation of quality factors, etc.) of TM010 disk resonators has been developed. The procedure is based on relating a very general description of HTS nonlinearities with the circuit elements of a nonlinear radial transmission line. This radial transmission line is then analyzed using the harmonic balance algorithm. Successful cross-checks are performed by comparing simulations with theoretical results obtained for a specific model of HTS nonlinearity. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated as well as its use for simulating filters with several inter-coupled disksDirect identification of extended defects as vortex pinning centers in melt textured YBa/sub 2/Cu/sub 3/O/sub 7/-Y/sub 2/BaCuO/sub 5/ composites
http://hdl.handle.net/2117/86320
Direct identification of extended defects as vortex pinning centers in melt textured YBa/sub 2/Cu/sub 3/O/sub 7/-Y/sub 2/BaCuO/sub 5/ composites
Puig Molina, Teresa; Obradors i Berenguer, Francesc Xavier; Martinez, B; Sandiumenge, F; O'Callaghan Castellà, Juan Manuel; Rabier, J
Single domain YBa/sub 2/Cu/sub 3/O/sub 7/-Y/sub 2/BaCuO/sub 5/ melt textured ceramic composites have revealed a very rich microstructure, which has usually impeded, by using standard measurements, to evaluate the contribution of each defect to the enhancement of the critical current. We have measured the in-plane magnetoresistance anisotropy and the anisotropic in-plane inductive critical currents and we show that together with the microstructural TEM analysis, the contribution of the different extended pinning centers can be separated. These results have allowed us to infer the kind of microstructure modifications required to improve the critical current. In particular, we present an isostatic pressing deformation technique as a very promising post-processing treatment to strongly increase the critical currents of these composites
2016-04-28T08:41:48ZPuig Molina, TeresaObradors i Berenguer, Francesc XavierMartinez, BSandiumenge, FO'Callaghan Castellà, Juan ManuelRabier, JSingle domain YBa/sub 2/Cu/sub 3/O/sub 7/-Y/sub 2/BaCuO/sub 5/ melt textured ceramic composites have revealed a very rich microstructure, which has usually impeded, by using standard measurements, to evaluate the contribution of each defect to the enhancement of the critical current. We have measured the in-plane magnetoresistance anisotropy and the anisotropic in-plane inductive critical currents and we show that together with the microstructural TEM analysis, the contribution of the different extended pinning centers can be separated. These results have allowed us to infer the kind of microstructure modifications required to improve the critical current. In particular, we present an isostatic pressing deformation technique as a very promising post-processing treatment to strongly increase the critical currents of these compositesNumerical Optimization of Hybrid Dielectric/HTS Resonator for Surface Impedance Evaluation of HTS Films
http://hdl.handle.net/2117/86318
Numerical Optimization of Hybrid Dielectric/HTS Resonator for Surface Impedance Evaluation of HTS Films
Collado Gómez, Juan Carlos; Gonzalo, D; Rozan, E; O'Callaghan Castellà, Juan Manuel
This work describes an alternative to the traditional dielectric resonator topology used for measuring surface impedance in high temperature superconducting (HTS) films. A gap is introduced above the dielectric so that only the lower film is in direct contact with it. This arrangement has been used extensively for mechanical tuning of dielectric resonators and, when used for surface impedance measurement, it can be designed to make the losses in the upper film small relative to the overall resonator losses. Then, measured results are mostly due to one of the films and not the average of two. The specifics of a resonator design for measuring 2-inch wafers are presented. An analysis and optimization of the resonator is done using a numerically efficient mode-matching algorithm
2016-04-28T08:30:47ZCollado Gómez, Juan CarlosGonzalo, DRozan, EO'Callaghan Castellà, Juan ManuelThis work describes an alternative to the traditional dielectric resonator topology used for measuring surface impedance in high temperature superconducting (HTS) films. A gap is introduced above the dielectric so that only the lower film is in direct contact with it. This arrangement has been used extensively for mechanical tuning of dielectric resonators and, when used for surface impedance measurement, it can be designed to make the losses in the upper film small relative to the overall resonator losses. Then, measured results are mostly due to one of the films and not the average of two. The specifics of a resonator design for measuring 2-inch wafers are presented. An analysis and optimization of the resonator is done using a numerically efficient mode-matching algorithmDesign and fabrication of coplanar YBCO structures on lithium niobate substrates
http://hdl.handle.net/2117/86315
Design and fabrication of coplanar YBCO structures on lithium niobate substrates
Rozan, Edouard; Collado Gómez, Juan Carlos; Garcia, Alfredo; O'Callaghan Castellà, Juan Manuel; Pous Andrés, Rafael; Fàbrega Sanchez, Lourdes; Rius Casals, Juan Manuel; Rubí, R; Fontcuberta, J; Harackiewicz, F
YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) with low RF losses has been successfully deposited onto lithium niobate (LNO) to improve the performance of electrooptic Mach-Zender modulators. Epitaxial, c-axis oriented superconducting YBCO thin films have been grown on X-cut LNO single crystals with a yttria-stabilized zirconia (YSZ) buffer layer by RF magnetron sputtering. This buffer layer is needed to obtain good superconducting properties of the YBCO grown. Numerical tools have been developed to analyze CPW structures based on YBCO/YSZ/LNO trilayers, and they indicate that YSZ thickness has to be kept to the minimum necessary for good YBCO growth. With this restriction, the RF losses of YBCO/YSZ/LNO samples have been measured. The results from these measurements are used to quantify the performance enhancement in a Mach-Zender modulator using YBCO electrodes
2016-04-28T08:18:45ZRozan, EdouardCollado Gómez, Juan CarlosGarcia, AlfredoO'Callaghan Castellà, Juan ManuelPous Andrés, RafaelFàbrega Sanchez, LourdesRius Casals, Juan ManuelRubí, RFontcuberta, JHarackiewicz, FYBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) with low RF losses has been successfully deposited onto lithium niobate (LNO) to improve the performance of electrooptic Mach-Zender modulators. Epitaxial, c-axis oriented superconducting YBCO thin films have been grown on X-cut LNO single crystals with a yttria-stabilized zirconia (YSZ) buffer layer by RF magnetron sputtering. This buffer layer is needed to obtain good superconducting properties of the YBCO grown. Numerical tools have been developed to analyze CPW structures based on YBCO/YSZ/LNO trilayers, and they indicate that YSZ thickness has to be kept to the minimum necessary for good YBCO growth. With this restriction, the RF losses of YBCO/YSZ/LNO samples have been measured. The results from these measurements are used to quantify the performance enhancement in a Mach-Zender modulator using YBCO electrodes