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• Joint Meeting: "VI Encuentro Ibérico de Electromagnetismo Computacional", "II LEMA-EPFL Workshop on Integral Techniques for Electromagnetics"

  

3.- Results.

In this section we include those book chapters, journal papers and conference papers reporting original results of the project.

Some bibliometric statistics (extracted from ISI Web of Knowledge, Thomson Reuters) regarding source distributions, international collaborations and citation can be found HERE.

• JOURNAL PAPERS
  1. R. Yang, R. Rodríguez-Berral, F. Medina, and Y. Hao, "Analytical model for the transmission of electromagnetic waves through arrays of slits in perfect conductors and lossy metal screens," Journal of Applied Physics, 109, 103107, May 2011.

     Abstract: This paper presents a very simple analytical model for the analysis of the resonant transmission of microwaves or millimeter waves through periodically distributed slits in a thick metal screen. The model is based on equivalent circuits consisting of transmission line elements of known characteristic admittances and propagation constants loaded by capacitors. Closed-form analytical expressions are provided for all the circuit parameters. Alternatively, the circuit parameters can be quickly computed from numerical simulations carried out at a few frequency points. The proposed analytical model accounts for all the details of the observed transmission spectrum, including conventional Fabry-Perot (FP) resonances, which are controlled by the thickness of the screen, as well as extraordinary transmission peaks, which are related to the periodicity. The range of validity of the model as a function of dimensional parameters is discussed. The experimentally observed and numerically predicted redshift of the Fabry-Pérot transmission peaks with respect to the ideal Fabry-Pérot resonance condition is accurately accounted for by the capacitors of the model. For narrow slits, the extraordinary transmission peak is linked to the singular behavior of the capacitances at the Rayleigh-Wood anomaly frequency point. Finally, the effect of the lossy nature of the metal screens is included in the model, providing accurate predictions of the transmission losses. Additionally, for lossy screens the model adequately predicts the anomalous behavior of the above mentioned redshift when the slit width becomes comparable to the skin depth in the metal, which is in good agreement with experimental and theoretical data previously reported for a single slit.

  2. Ana L. Fructos, S. Campione, F. Capolino, F. Mesa, "Characterization of complex plasmonic modes in two-dimensional periodic arrays of metal nanospheres," Journal of the Optical Society of America B, 28, pp. 1446-1458, June 2011.

     Abstract: Two-dimensional periodic arrays of noble metal nanospheres support a variety of optical phenomena, including bound and leaky modes of several types. The scope of this paper is the characterization of the modal dispersion diagrams of planar arrays of silver nanospheres, with the ability to follow individual modal evolutions. The metal spherical nanoparticles are described using the single dipole approximation technique by including all the retarded dynamic field terms. Polarizability of the nanospheres is provided by the Mie theory. Dispersion diagrams for both physical and nonphysical modes are shown for a square lattice of Ag nanospheres for the case of lossless and lossy metal particles, with dipole moments polarized along the x, y, and z directions. Though an array with one set of parameters has been studied, the analysis method and classification are general. The evolution of modes through different Riemann sheets and analysis of guidance and radiation are studied in detail.

  3. Ana L. Fructos, Rafael R. Boix, Francisco Mesa, "Efficient computation of the off-diagonal elements of the vector-potential multilayered periodic dyadic Green's function," IEEE Transactions on Antennas and Propagation, 59, no. 7, pp. 2557-2564, July 2011.

     Abstract: The authors focus on the efficient computation of the slowly convergent infinite series that lead to the off-diagonal elements of the vector potential multilayered periodic dyadic Green's function. Two different approaches based on Kummer's transformation are applied to the evaluation of these series. The well-known approach that makes use of the generalized pencil of functions (GPoF) and EwaldÂ’s method is the fastest approach, but it does not provide accurate results when the distance between the field point and any of the source points is close to zero. To avoid this problem, we present a novel approach based on the GPoF and the spectral Kummer-PoissonÂ’s method with higher-order asymptotic extraction. This latter approach is slightly slower than the former one, but it is accurate in the whole range of distances between the field point and the sources.

  4. Y. R. Padooru, A. B. Yakovlev, C. S. R. Kaipa, F. Medina, and F. Mesa, "Circuit modeling of multiband high-impedance surface absorbers in the microwave regime," Physical Review B, 84, art. 035108, July 2011.

     Abstract: In this paper, we present a simple circuit model to study the absorption of electromagnetic waves by a multilayer structure with a high impedance surface in the microwave regime. The absorber consists of a stack of two- dimensional arrays of sub-wavelength meshes or patches separated by dielectric slabs and backed by a metallic ground plane, with a single resistive sheet placed on the top layer. We observe the appearance of low-frequency resonances of total absorption, which have been identified as the resonances of Fabry-Perot type associated with the individual reactively loaded dielectric slabs (that are strongly coupled through the subwavelength grids). It is shown that these resonances lie within certain characteristic frequency band defined by the structural parameters of the absorber. The observed resonances are characterized by studying the electromagnetic field behavior using the circuit model and full-wave numerical program. In addition, we show that the patch array absorber provides stable resonances with respect to the angle and the polarization of obliquely incident plane waves.

  5. J.M. Algarín, M.J. Freire, R. Marqués, "Comparative analysis of the transfer function of closed and open split-ring metamaterial slab lenses," Metamaterials, 5, no. 7, pp. 107-111, June/sept. 2011.

     Abstract: The transfer function of some in-plane periodic split-ring metamaterial slab lenses is analyzed for several configurations across the slab. The transfer function is obtained by means of full-wave electromagnetic computations using the simulation software CST Microwave Studio, and it is compared with the transfer function obtained analytically for a continuous slab of reference. Significant differences are found in the transfer function of the analyzed structures. The closest behavior to the continuous slab lens was found for the partially open structure comprising an integer number of periods across the slab. Experiments are provided which confirms the theoretical results.

  6. L. Jelinek, J.D. Baena, J. Voves and R. Marqués, "Metamaterial-inspired perfect tunnelling in semiconductor heterostructures," New Journal of Physics, 13, art. 083011, 2011.

     Abstract: In this paper, we use a formal analogy of the electromagnetic wave equation and the Schrödinger equation in order to study the phenomenon of perfect tunnelling (tunnelling with unitary transmittance) in a one-dimensional semiconductor heterostructure. Using the Kane model of a semiconductor, we show that this phenomenon can indeed exist, resembling all the interesting features of the corresponding phenomenon in classical electromagnetism in which metamaterials (substances with negative material parameters) are involved. We believe that these results can pave the way toward interesting applications in which metamaterial ideas are transferred into the semiconductor domain.

  7. R Marqués, L. Jelinek, M. J. Freire, J. D. Baena, and M. Lapine, "Bulk Metamaterials Made of Resonant Rings," Proceedings of the IEEE, 99, no. 10, pp. 1660-1668, Oct. 2011. (Review paper, invited paper)

     Abstract: In this brief review, we present the fundamentals of bulk resonant ring metamaterial (RRM) theory. Metamaterials made of resonant rings are discussed, and some basic design rules are provided. Homogenization (including spatial dispersion) of 3-D resonant ring latices is reviewed, with emphasis in isotropic designs. Edge effects in finite size metamaterial samples are discussed. Finally, possible applications and future trends are briefly reviewed.

  8. V. Delgado, R. Marqués, "Surface impedance model for extraordinary transmission in 1D metallic and dielectric screens," Optics Express, 19, no. 25, pp. 25290-25297, Nov. 2011.

     Abstract: Extraordinary Optical Transmission of TM waves impinging at oblique incidence on metallic or high permittivity dielectric screens with a periodic distribution of 1D slits or any other kind of 1D defects is analyzed. Generalized waveguide theory altogether with the surface impedance concept are used for modeling such phenomena. A numerical analysis based on the mode matching technique proves to be an efficient tool for the characterization of these structures for any angle of incidence and slit or defect apertures.

  9. J.M Algarín, M.A. López, M.J. Freire, and R. Marqués, "Signal-to-noise ratio evaluation in resonant ring metamaterial lenses for MRI applications," New Journal of Physics, 13, 115006 (12 pp.), Nov. 2011.

     Abstract: In this paper, we present a method for the evaluation of the signal-to-noise ratio in magnetic resonance imaging (MRI) coils loaded with resonant ring metamaterial lenses, in the presence of a conducting phantom resembling human tissue. The method accounts for the effects of the discrete and finite structure of the metamaterial. Numerical computations are validated with experimental results, including laboratory measurements and MRI experiments.

  10. J.C. Miñano, R. Marqués, J.C. González, P. Benítez, V. Delgado, D. Grabovickic, M. Freire, "Super-resolution for a point source better than lambda /500 using positive refraction," New Journal of Physics, 13, 125009(14 pp.), Dec. 2011.

      Abstract: Leonhardt (2009 New J. Phys. 11 093040) demonstrated that the two-dimensional (2D) Maxwell fish eye (MFE) lens can focus perfectly 2D Helmholtz waves of arbitrary frequency; that is, it can transport perfectly an outward (monopole) 2D Helmholtz wave field, generated by a point source, towards a "perfect point drain" located at the corresponding image point. Moreover, a prototype with lambda/5 super-resolution property for one microwave frequency has been manufactured and tested (Ma et al 2010 arXiv:1007.2530v1; Ma et al 2010 New J. Phys. 13 033016). However, neither software simulations nor experimental measurements for a broad band of frequencies have yet been reported. Here, we present steady-state simulations with a non-perfect drain for a device equivalent to the MFE, called the spherical geodesic waveguide (SGW), which predicts up to lambda/500 super-resolution close to discrete frequencies. Out of these frequencies, the SGW does not show super-resolution in the analysis carried out.

  11. R. Rodríguez-Berral, F. Medina, F. Mesa, M. García-Vigueras, "Quasi-analytical Modeling of Transmission/Reflection in Strip/Slit Gratings Loaded with Dielectric Slabs," IEEE Transactions on Microwave Theory and Techniques, 60, no. 3, pp. 405-418, March 2012.

      Abstract: This paper presents a quasi-analytical approach to study the classic topic of transmission/reflection of electromagnetic waves through 1-D periodic arrays of strips/slits in metal screens. The approach is based on standard waveguide discontinuity theory. Starting from field equations, it is inferred a circuit-like reduced-order model with just one parameter to be determined. The value of this parameter can be obtained from the transmission/reflection coefficient provided by any full-wave method at just one single frequency. In this way, the computation effort to obtain very wide-band responses of periodically distributed slits or strips under oblique TE/TM illumination in the presence of loading dielectric slabs is reduced to the full-wave analysis of the structure at a single frequency value. For relatively narrow strip/slit gratings, this procedure gives very accurate results even for very complicated transmission/reflection spectra. An additional advantage of the present approach is that it allows for an easy understanding of the underlying physics of the phenomena involved.

  12. A. Fernández-Prieto, J. Martel, F. Medina, F. Mesa, "Bandpass and Bandstop Filters Based on Open Stubs with Slots in the Ground Plane," Microwave and Optical Technology Letters, 54, no. 5, pp. 1242-1246, May 2012.

      Abstract: This work reports on a modified version of lambda/2 open stubs bandpass filters (lambda/2-OSBPFs) and lambda/4 open stubs bandstop filters (lambda/4-OSBSFs) for wide/narrow bandwidth operation. When wide bandwidths (for lambda/2-OSBPF) or narrow bandwidths (for lambda/4-OSBSF) are required, conventional microstrip implementation of this kind of filters is not possible owing to unattainable high stub characteristic impedance values, which lead to extremely narrow strips. To overcome this drawback, we propose the introduction of slots under the stubs along the grounded backside of the substrate. This provides additional flexibility for the width of the strips printed on the upper side of the substrate, which can be much wider than without the slots. To avoid undesired resonances of the slot mode and radiation problems, printed narrow strip short circuits are distributed along the slotted regions. It is shown that the presence of these strips does not meaningfully affect the filter performance while suppresses the undesired slot mode effects.

  13. M. J. Freire, M. A. López, J. M. Algarin, F. Breuer, R. Marqués, "Image acceleration in parallel magnetic resonance imaging by means of metamaterial magnetoinductive lenses," AIP Advances, 2, art. 022136, May 2012.

      Abstract: Parallel Magnetic Resonance imaging (pMRI) is an image acceleration technique which takes advantage of localized sensitivities of multiple receivers. In this letter, we show that metamaterial lenses based on capacitively-loaded rings can provide higher localization of coil sensitivities compared to conventional loop designs. Several lens designs are systematically analyzed in order to find the structure providing higher signal-to-noise-ratio. The magnetoinductive (MI) lens has been found to be the optimum structure and an experiment is developed to show it. The ability of the MI lens for MRI is investigated by means of the parameter known in the MRI community as g-Factor.

  14. C.S.R. Kaipa, A. B. Yakovlev, G. W. Hanson, Y. R. Padooru, F. Medina, F. Mesa, "Enhanced transmission with a graphene-dielectric micro-structure at low-terahertz," Physical Review B (Condensed Matter and Materials Physics), 85, no. 24, pp. 245407-(1-6), June 2012.

      Abstract: Here, we report on the transmissivity of electromagnetic waves through a stack of monolayer graphene sheets separated by dielectric slabs at low-terahertz frequencies. It is observed that the multilayer structure possesses band-gap properties and supports a series of bandpass and band-stop regions, similar to the cases of stacked metallic meshes separated by dielectric slabs at microwave/THz frequencies and a metal-dielectric stack at optical frequencies. The transmission resonances in the bandpass region are identified as coupled Fabry-Pérot resonances associated with the individual cavities of dielectric slabs loaded with graphene sheets. It is also noticed that these resonances lie within a certain characteristic frequency band, independent of the number of layers in the graphene-dielectric stack. The study is carried out using a simple analytical transfer-matrix approach or, equivalently, a circuit-theory model, resulting in the exact solution for the multiple dielectric/graphene sheet surface-conductivity model. Also, an independent verification of the observed phenomena is obtained with commercial numerical simulations.

  15. El-Mokhtar Hamham, F. Mesa, F. Medina, M. Khalladi, "Surface-impedance quasi-transverse electromagnetic approach for the efficient calculation of conductor losses in multilayer single and coupled microstrip lines," IET Microwaves, Antennas & Propagation, 6, no. 5, pp. 519-526, June 2012.

      Abstract: In this study the authors present a new surface-impedance model for the accurate computation of the effect of metal losses on the parameters of printed microstrip lines. The novelty of the authors approach lies in the fast and direct calculation of the tangential magnetic fields above and below the strip conductors, which allows us to develop a very efficient quasi-transverse electromagnetic (TEM) solution for the conductor losses of multilayer single or coupled microstrip lines. The overall computational effort of the authors method is much less than that required by purely numerical approaches. The accuracy of the method has been verified by comparison with other techniques, including a general-purpose full-wave finite elements method. It is also shown that the proposed method provides better results than other previously surface-impedance approaches.

  16. M. Lapine, L. Jelinek, R. Marqués, "Surface mesoscopic effects in finite metamaterials," Optics Express, 20, no. 16, pp. 18297-18302, July 2012.

      Abstract: While the effective medium treatment of unbounded metamaterials appears to be well established and firmly proven, related phenomena in finite structures have not received sufficient attention. We report on mesoscopic effects associated with the boundaries of finite discrete metamaterial samples, which can invalidate an effective medium description. We show how to avoid such effects by proper choice of boundary configuration. As all metamaterial implementations are naturally finite, we are confident that our findings are crucial for future metamaterial research.

  17. C.S.R. Kaipa, A.B. Yakovlev, F. Medina, and F. Mesa, "Transmission through stacked 2-D periodic distributions of square conducting patches," Journal of Applied Physics, 112, pp. 033101-(1-11), August 2012.

      Abstract: In this paper, we study the transmissivity of electromagnetic waves through stacked two-dimensional printed periodic arrays of square conducting patches. An analytical circuit-like model is used for the analysis. The model accounts for the details of the transmission spectrum provided that the period of the unit cell of each patterned layer is well below the wavelength in the dielectric slabs separating the printed surfaces. In particular, we analyze the low-pass band and rejection band behavior of the multilayer structure, and the results are validated by comparison with a computationally intensive finite element commercial electromagnetic solver. The limiting case of an infinite periodic structure is analytically solved and the corresponding band structure is used to explain the passband/stopband behavior of finite structures. In addition, we study in depth the elementary unit cell consisting of a single dielectric slab coated by two metal patch arrays, and its resonance behavior is explained in terms of Fabry-Pérot resonances when the electrical thickness the slab is large enough. In such case, the concept of equivalent thickness of the equivalent ideal Fabry-Pérot resonator is introduced. For electrically thinner slabs it is also shown that the analytical model is still valid, and its corresponding first transmission peak is explained in terms of a lumped-circuit LC resonance.

  18. J. Naqui, M. Durán-Sindreu, A. Fernández-Prieto, F. Mesa, F. Medina, F. Martín, "Multimode Propagation and Complex Waves in CSRR-based Transmission Line Metamaterials," IEEE Antennas and Wireless Propagation Letters, 11, pp. 1024-1027, September 2012.

      Abstract: Transmission-line metamaterials based on complementary split-ring resonators (CSRRs) are shown to support forward, backward, electroinductive, and complex waves. Two CSRR-based lines are considered: 1) stopband microstrip lines simply loaded with CSRRs, and 2) passband microstrip lines loaded with CSRRs and series gaps. The effects of interresonator coupling on bandwidth enhancement are analyzed on the basis of Bloch mode theory by considering the lumped-element equivalent 4-port circuit model of the unit cell. All the propagation modes are captured by the proposed multiterminal Bloch mode theory, from an eigenmode analysis. The results are validated through a commercial eigenmode solver and supported by experimental data.

  19. J. Naqui, A. Fernández-Prieto, M. Durán-Sindreu, F. Mesa, J. Martel, F. Medina, F. Martín, "Common-mode Suppression in Microstrip Differential Lines by Means of Complementary Split Ring Resonators: Theory and Applications," IEEE Transactions on Microwave Theory and Techniques, 60, no. 10, pp. 3023-3034, October 2012.

      Abstract: This paper is focused on the application of complementary split-ring resonators (CSRRs) to the suppression of the common (even) mode in microstrip differential transmission lines. By periodically and symmetrically etching CSRRs in the ground plane of microstrip differential lines, the common mode can be efficiently suppressed over a wide band whereas the differential signals are not affected. Throughout the paper, we present and discuss the principle for the selective common-mode suppression, the circuit model of the structure (including the models under even- and odd-mode excitation), the strategies for bandwidth enhancement of the rejected common mode, and a methodology for common-mode filter design. On the basis of the dispersion relation for the common mode, it is shown that the maximum achievable rejection bandwidth can be estimated. Finally, theory is validated by designing and measuring a differential line and a balanced bandpass filter with common-mode suppression, where double-slit CSRRs (DS-CSRRs) are used in order to enhance the common-mode rejection bandwidth. Due to the presence of DS-CSRRs, the balanced filter exhibits more than 40 dB of common-mode rejection within a 34% bandwidth around the filter pass band.

  20. M. García-Vigueras, F. Mesa, F. Medina, R. Rodríguez-Berral, J. L. Gómez-Tornero, "Simplified circuit model for metallic arrays of patches sandwiched between dielectric slabs under arbitrary incidence," IEEE Transactions on Antennas and Propagation, 60, no. 10, pp. 4637-4649, October 2012.

      Abstract: This work presents an equivalent circuit to model the transmission/reflection of a plane wave that impinges obliquely on a periodic arrangement of metallic rectangular dipoles embedded between two dielectric slabs. The equivalent circuit takes advantage of the periodicity of the structure to reformulate the original problem as a certain equivalent waveguide scattering problem. Equivalent transmission lines are used to simulate the wave propagation whereas equivalent lumped circuit elements account for presence of the metallic patches. The obtaining of the circuit parameters is carried out via a systematic procedure, which provides a robust strategy that gives rise to surprisingly accurate results even for rather complex situations. The proposed equivalent circuit model simplifies considerably the original complex electromagnetic problem and provides a valuable physical insight into the parameters that are relevant in the phenomenon as well as an in-depth understanding of the operation principles of the periodic surface. Thus, the reported reduced-order model of the corresponding scattering problem can be a very convenient and helpful tool for the analysis and/or design of many practical devices.

  21. Y. R. Padooru, A. B. Yakovlev, C. S. R. Kaipa, G. W. Hanson, F. Medina, F. Mesa, A. W. Glisson, "New Absorbing Boundary Conditions and Analytical Model for Multilayered Mushroom-Type Metamaterials: Applications to Wideband Absorbers," IEEE Transactions on Antennas and Propagation, 60, no. 12, pp. 5727-5742, December 2012.

      Abstract: An analytical model is presented for the analysis of multilayer wire media loaded with 2-D arrays of thin material terminations, characterized in general by a complex surface conductivity. This includes the cases of resistive, thin metal, or graphene patches and impedance ground planes. The model is based on the nonlocal homogenization of the wire media with additional boundary conditions (ABCs) at the connection of thin (resistive) material. Based on charge conservation, new ABCs are derived for the interface of two uniaxial wire mediums with thin imperfect conductors at the junction. To illustrate the application of the analytical model and to validate the new ABCs, we characterize the reflection properties of multilayer absorbing structures. It is shown that in such configurations the presence of vias results in the enhancement of the absorption bandwidth and an improvement in the absorptivity performance for increasing angles of an obliquely incident TM-polarized plane wave. The results obtained using the analytical model are validated against full-wave numerical simulations.

  22. R. Rodríguez-Berral, C. Molero, F. Medina, F. Mesa, "Analytical Wideband Model for Strip/Slit Gratings Loaded with Dielectric Slabs," IEEE Transactions on Microwave Theory and Techniques, 60, no. 12, pp. 3908-3918, December 2012.

      Abstract: This paper presents a fully analytical model to determine the transmission and reflection properties of planar 1-D distributions of metal strips or slits made in thin metal screens. In contrast with other analytical or quasi-analytical approaches, the formulation incorporates the presence of dielectric slabs and is valid over a wide frequency band, from the long wavelength limit to the grating lobes operation. The model has been adapted to the case where two 1-D planar grids are stacked or a single grid is printed on a grounded substrate. In these cases, the model rigorously takes into account higher order mode interaction between the two stacked arrays of strips/slits or with the ground plane. Oblique incidence and both TE and TM polarizations have been considered. The analytical results show a good agreement with those computed by high-performance numerical methods, accounting for very fine details of extremely complicated transmission/reflection spectra. These results are of straightforward application to a variety of practical situations from microwaves to the terahertz regime. The present methodology can still be useful at higher frequencies provided that adequate models of the planar conductors are incorporated. In general, the model provides physical insight on the nature of the expected spectra and facilitates the design of devices based on planar metallic gratings.

  23. D. González-Ovejero, F. Mesa, C. Craeye, "Accelerated Macro Basis Functions Analysis of Finite Printed Antenna Arrays Through 2D and 3D Multipole Expansions," IEEE Transactions on Antennas and Propagation, 61, no. 2, pp. 707-716, February 2013.

      Abstract: An efficient technique is presented for the analysis of finite printed antenna arrays made of identical elements. It is based on a closed-form expression for the spatial-domain Green's function (GF) given as a finite sum of cylindrical waves (obtained through rational function fitting) plus one spherical wave. From there, a multipole expansion can be obtained for planar layered medium GFs. The macro basis function (MBF) technique is applied to the method of moments (MoM) solution of a mixed-potential integral equation, this reduces the size of the MoM impedance matrix and allows for a direct solution. However, the evaluation of the entries of this reduced matrix becomes the dominant contribution to the total computation time. The aforementioned multipole expansion is exploited to provide a fast construction of the reduced MoM matrix, whose elements are the reaction integrals between the MBFs considered to characterize the currents on the array element. The complexity of evaluating the interactions between MBFs is found to be dominated by the calculations related to the spherical wave term. Thus, taking into account the layered medium does not increase the order of the complexity with respect to a multipole-accelerated computation of reaction integrals in a homogeneous medium.

  24. Y. R. Padooru, A. B. Yakovlev, C. S. R. Kaipa, G. W. Hanson, F. Medina, F. Mesa, "Dual capacitive-inductive nature of periodic graphene patches: transmission characteristics at low-terahertz frequencies," Physical Review B, 87, pp. 115401 (10 pp.), March 2013.

      Abstract: We report on the dual nature (capacitive and inductive) of the surface impedance of periodic graphene patches at low-terahertz frequencies. The transmission spectra of a graphene-dielectri1c stack shows that patterned graphene exhibits both the low-frequency (capacitive) passband of metal patch arrays and the higher-frequency (inductive) passband of metal aperture arrays in a single tunable configuration. The analysis is carried out using a transfer-matrix approach with two-sided impedance boundary conditions, and the results are verified using full-wave numerical simulations. In addition, the Bloch-wave analysis of the corresponding infinite periodic structure is presented in order to explain the passband and stopband characteristics of the finite graphene-dielectric stack.

  25. V. Delgado, R. Marqués, L. Jelinek, "Coupled-wave surface-impedance analysis of extraordinary transmission through single and stacked metallic screens," IEEE Transactions on Antennas and Propagation, 61, no. 3, pp. 1342-1351, March 2013.

      Abstract: In this paper, we present an efficient coupled-wave surface-impedance method for the analysis of extraordinary optical transmission (EOT) through single and stacked realistic metallic screens under normal and oblique incidence, including possible dielectric interlayers. The proposed theory is valid for the complete frequency range where EOT has been reported, including microwaves and optics. Electromagnetic simulations validate the results of the model, which enable fast and accurate characterization of the analyzed structures.

  26. A. Fernández-Prieto, J. Martel, F. Mesa, S. Qian, F. Medina, J.-S. Hong, J. Naqui, F. Martin, "Dual-band differential filter using broad-band common-mode rejection artificial transmission line," Progress in Electromagnetics Research-PIER, 139, pp. 779-797, May 2013.

      Abstract: A new balanced dual-band bandpass filter with strong common-mode rejection is presented in this paper. Common-mode rejection is provided by a section of a periodic microstrip differential line that behaves as a low-pass filter under common-mode operation. In contrast, the differential line exhibits very good all-pass behavior under differential mode operation. This structure is combined with a differential dual-band bandpass filter based on embedded resonators. Simulations and experiments confirm that the combined structure has good common-mode rejection within the passbands of the dual-band differential filter.

  27. M.J. Freire, M.A. López, F. Meise, J.M. Algarín, P.M. Jakob, M. Bock, R. Marqués, "A Broadside-Split-Ring Resonator-Based Coil for MRI at 7 T," IEEE Transactions on Medical Imaging, 32, no. 6, pp. 1081-1084, June 2013.

      Abstract: A coil design termed as broadside-coupled loop (BCL) coil and based on the broadside-coupled split ring resonator (BC-SRR) is proposed as an alternative to a conventional loop design at 7 T. The BCL coil has an inherent uniform current which assures the rotational symmetry of the radio-frequency field around the coil axis. A comparative analysis of the signal-to-noise ratio provided by BCL coils and conventional coils has been carried out by means of numerical simulations and experiments in a 7 T whole body system.

  28. J. D. Ortiz, J. D. Baena, V. Losada, F. Medina, R. Marqués, J. L. Araque Quijano, "Self-complementary metasurface for designing narrow band pass/stop filters," IEEE Microwave and Wireless Components Letters, 23, no. 6, pp. 291-294, June 2013.

      Abstract: A self-complementary metasurface is studied in this paper. The metasurface is a 2D periodical arrangement of unit cells formed by a metallic printed split ring resonator and its complementary counterpart. It is demonstrated that this structure behaves like a very selective band-pass filter for a certain linear polarization while band-stop filtering is achieved for the orthogonal polarization over the same frequency range. This idea opens the door to a new class of frequency selective surfaces made of connected and unconnected elements, whose filtering properties are mechanically tunable from band-pass to band-stop by rotating the surface or the polarization.

  29. R. Florencio, R. R. Boix, E. Carrasco, J. A. Encinar, V. Losada, "Efficient numerical tool for the analysis and design of reflectarrays based on cells with three parallel dipoles," Microwave and Optical Technology Letters, 55, no. 6, pp. 1212-1216, June 2013.

      Abstract: In this article, the Method of Moments in the spectral domain (MoM-SD) is applied to the analysis of multilayered periodic structures, containing three coplanar parallel dipoles in the unit cell. It is shown that the use of basis functions with edge singularities in the modeling of the current density on the dipoles leads to important computer memory and CPU times savings in the analysis of the periodic structures. The MoM-SD home-made software is used in the analysis of a shaped beam reflectarray antenna made of cells with three parallel dipoles under the local periodicity assumption. The numerical results obtained for the radiation pattern of the antenna are compared with numerical results provided by the commercial software CSTV and with measurements and good agreement is found.

  30. S. Campione, F. Mesa, F. Cappolino, "Magnetoinductive waves and complex modes in two-dimensional periodic arrays of split-ring resonators," IEEE Transactions on Antennas and Propagation, 61, no. 7, pp. 3554-3563, July 2013.

      Abstract: We investigate magnetoinductive waves in two-dimensional periodic arrays of split ring resonators or capacitively loaded loops and characterize the modes with real and complex wavenumber excitable in such arrays. Each resonator is modeled as a single magnetic dipole, and the computation of the modal wavenumbers is performed by searching for the zeroes of the homogeneous scalar equation characterizing the field in the array. We provide original developments for the Ewald method applied to the required dyadic periodic Green's function for the array of magnetic dipoles, including the quasi-static case. The Ewald representation is analytically continued into the complex wavenumber space and also provides series with Gaussian convergence rate. In particular, we analyze and classify proper, improper, forward, backward, bound, and leaky magnetoinductive waves varying frequency and compare the fully retarded solution to the quasi-static one. The importance of accounting for field retardation effects for the prediction of the physical waves excitable in the array when it is not very subwavelength is highlighted. The proposed method complements previous investigations and is a powerful tool for the design of waveguiding or radiating structures based on magnetoinductive waves.

  31. S. El Amrani, R. Rodríguez-Berral, F. Mesa, M. Boussouis, "Comprehensive study of the spurious effects on the signal guidance in coplanar waveguides," IEEE Transactions on Electromagnetic Compatibility, 55, no. 4, pp.707-716, August 2013.

      Abstract: A study of the propagation characteristics and several signal integrity aspects of a conventional coplanar waveguide (CPW) is presented here. The study considers the bound and leaky modes supported by this structure up to high frequencies. The analysis of the dispersion characteristics of the structure is complemented with the study of the voltage excited along the line when fed by a delta-gap source of current. The results thus obtained allow us to discuss on the physical meaning of the modes and the relevance of the residual wave, which is key to link the practical role played by the different modal solutions with the spurious effects that may appear in the structure. The analysis of the eye-diagram performance also reveals that the signal integrity in CPW systems basically relies on the excitation of the parasitic fundamental coupled slotline mode as well as the high-frequency excitation of the continuous spectrum. These aspects have been studied in detail.

  32. S. El Amrani, R. Rodríguez-Berral, F. Mesa, "Effects of the bottom ground plate on CPW structures," IET Microwaves, Antennas and Propagation, 7, no. 8, pp. 708-713, August 2013.

      Abstract: In this paper we study the significant practical effects caused by the presence of a conductor plate beneath a coplanar waveguide (CPW) structure. Specifically we pay attention to the effects on the dispersion characteristics of the bound modes and on the signal integrity. This study allows us to discuss the reported proposal on the use of this additional conductor plate as an inexpensive alternative to air-bridges in order to alleviate the possible spurious effects produced by the potential existence of asymmetries in CPW-based circuits.

  33. J.D. Ortiz, J.D. Baena, V. Losada, F. Medina, J.L. Araque-Quijano, "Spatial Angular Filtering by FSSs Made of Chains of Interconnected SRRs and CSRRs," IEEE Microwave and Wireless Components Letters, 23, no. 9, pp. 477-479, September 2013.

      Abstract: Two frequency selective surfaces (FSSs) made of an infinite set of parallel 1-D chains of interconnected split ring resonators (I-SRRs) and interconnected complementary split ring resonators (I-CSRRs) are studied. The main result was that the central frequencies of the stopband and passband can be strongly tuned by controlling the angle of incidence.

  34. R. Florencio, R. R. Boix, J. A. Encinar, "Enhanced MoM analysis of the scattering by periodic strip gratings in multilayered substrates," IEEE Transactions on Antennas and Propagation, 61, no. 10, pp. 5088-5099, October 2013.

      Abstract: The method of moments (MoM) is applied to the analysis of the scattering of a multilayered periodic strip grating by a plane wave with oblique incidence and arbitrary polarization. Although this problem has been traditionally solved by means of the MoM in the spectral domain, this is an approach which leads to the computation of slowly convergent infinite summations. In this paper, the problem is solved by means of the mixed potential integral equation (MPIE) formulation of the MoM in the spatial domain. While applying the MoM in the spatial domain, two improvements are introduced which lead to important CPU time savings. First, the multilayered periodic Green's functions are accurately interpolated in terms of Chebyshev polynomials. Second, half the integrals involved in the computation of the MoM matrix entries are obtained in closed form. As a consequence of these two improvements, the spatial domain version of the MoM presented in this paper turns out to be between one and two orders of magnitude faster than the conventional spectral domain version when basis functions that account for edge singularities are used in the modeling of the current density on the metallizations.

  35. C. Molero, R. Rodríguez-Berral, F. Mesa, F. Medina, "Analytical Circuit Model for 1-D periodic T-Shaped Corrugated Surfaces," IEEE Transactions on Antennas and Propagation, 62, no. 2, pp. 794-803, February 2014.

      Abstract: An analytical circuit model is obtained to study the reflection of TM polarized electromagnetic waves that impinge obliquely on a one-dimensional periodic corrugated surface consisting of dielectric-loaded T-shaped planar corrugations backed by an infinite ground plane. The model is based on transmission line theory and equivalent lumped-element circuits. For the case of perfect conductors, the topology of the circuit is directly inferred from a rigorous full-wave formulation of the periodic problem without using any heuristic argument. This procedure leads to fully analytical expressions for all the circuit parameters. Ohmic losses are further incorporated in the model under the assumption of strong skin effect. The results thus obtained are compared with those given by an accurate Method of Moments numerical code and HFSS software showing a very good agreement. The strong numerical efficiency as well as the good physical insight provided by the present equivalent circuit model can be advantageously employed for the analysis and/or design of a variety of devices. As examples of the latter, the circuit model is used for the first-stage design of an electrically thin hard impedance surface, a corrugated surface that prevents specular reflection, and an absorber.

  36. J. Bernal, F. Mesa, D.R. Jackson, "Crosstalk in coupled microstrip lines with a top cover," IEEE Transactions on Electromagnetic Compatibility, 56, no. 2, pp. 375-384, April 2014.

      Abstract: In this paper, we investigate the influence of the excitation of improper radiating modes (leaky modes) in the propagation characteristics of coupled microstrip transmission lines. We calculate the crosstalk noise excited in the victim line and evaluate the impact of the presence of a metallic top cover due to the circuit packaging. The time domain propagation of pulses of different widths and rise times are computed in order to study the effect of the separation between the coupled strips on the crosstalk noise currents. We show that both even and odd leaky modes can be simultaneously excited on the covered microstrip structure at low frequencies. This can seriously compromise the signal integrity on the line because of the appearance of effects such as radiation, power loss, and interference, which are usually found in microstrip transmission lines at high frequencies. Our results are compared with those provided by a conventional analysis based on the quasi-TEM approximation and transmission line theory. For an open microstrip structure, we have found that the transmission line model accounts properly for the crosstalk current on the victim line. However, on covered coupled microstrip lines with a sufficiently low top-cover height, the crosstalk noise is higher than expected and cannot be accurately predicted by the transmission line model, even at frequencies where the cross section of the line is much smaller than the wavelength.

  37. J. Naqui, A. Fernández-Prieto, F. Mesa, F. Medina, F. Martín, "Effects of inter-resonator coupling in split ring resonator (SRR) loaded metamaterial transmission lines," Journal of Applied Physics, 115, pp. 375-384, 194903-(1-8), May 2014.

      Abstract: This paper investigates the effects of inter-resonator coupling in metamaterial transmission lines loaded with split ring resonators (SRRs). The study is performed from Bloch mode theory applied to the multiport equivalent circuit model of the unit cell of such artificial lines. From this analysis, it follows that the stopband bandwidth, inherent to SRR-loaded lines, is enhanced as inter-resonator coupling strengthens, and this enhancement is attributed to the presence of complex modes. The theoretical results are corroborated through calculation of the dispersion relation using a full-wave eigenmode solver, and also by measuring the frequency response of SRR-loaded lines with different inter-resonator distance and, hence, coupling.

  38. R. Bojanic, V. Milosevic, B. Jokanovic, F. Medina, F. Mesa, "Enhanced modelling of split-ring resonators couplings in printed circuits," IEEE Transactions on Microwave Theory and Techniques, 62, no. 8, pp. 1605-1615, August 2014.

      Abstract: An enhanced equivalent circuit approach for the magnetic/electric interaction of single split-ring resonators (SRRs) with printed lines is presented in this paper. A very simple and efficient lumped-element network is proposed to model the behavior of metamaterial-based printed lines over a wide frequency band. The same circuit topology can be used for the single- and two-mirrored SRRs loaded microstrip line. The corresponding circuit parameters are obtained from the multiconductor transmission line theory as well as from closed-form expressions that make use of just the resonance frequency and minimum of the reflection coefficient (which should be previously extracted from experiments or full-wave simulations). The comparison of our equivalent circuit results with measurements and full-wave simulations has shown a very good agreement in a considerably wider frequency band than other previously proposed simple equivalent circuits

  39. F. Mesa, M. García-Vigueras, F Medina, R. Rodríguez-Berral, J. R. Mosig, "Circuit-model analysis of frequency selective surfaces with scatterers of arbitrary geometry," IEEE Antennas and Wireless Propagation Letters, 14, pp. 135-139, 2015.

      Abstract: An equivalent-network model is here proposed to characterize two-dimensional planar periodic arrays of arbitrary scatterers/apertures embedded in a layered environment. The model is an extension of the approach previously developed by some of the authors, which only considered simple rectangular scatterers. A key underlying assumption in the present approach is that the current/field distribution in the scatterer can be factorized so that the spatial profile is independent of the frequency in the considered range of interest. This approximation is proven to work properly for a great variety of useful planar scatterer/aperture patterns, even at frequencies within the diffraction regime. The spatial current/field profile is determined from a full-wave simulation at a single and low frequency value. Our numerical results are validated through comparison to commercial simulators for very wide frequency ranges as well as with previously proposed circuit-model approaches.

  40. R. Rodríguez-Berral, F. Mesa, F. Medina, "Analytical multimodal network approach for 2-D arrays of planar patches/apertures embedded in a layered medium," IEEE Transactions on Antennas and Propagation, 63, no. 5, pp. 1969-1984, May 2014.

      Abstract: A fully analytical multimodal equivalent circuit is presented for the modeling of the scattering of an obliquely incident plane wave by a two-dimensional (2-D) periodic array of metallic patches (or apertures in a metallic screen) embedded in a layered medium. The topology of the equivalent network is rigorously derived in the analysis and all the network parameters are given in closed form. In contrast with the previously reported explicit circuit models, the proposed approach accounts for dynamical effects over a very wide frequency range, which enables the application of the model to a great variety of situations. The key advantages of the reported multimodal network representation are its analytical nature, its extremely low-computational cost and that the physical phenomena involved in the scattering can be easily understood in terms of transmission line and lumped circuital reasonings.

  41. A. Fernández-Prieto, A. Lujambio, J. Martel, F. Medina, F. Mesa, R. R. Boix, "Simple and compact balanced bandpass filters based on magnetically coupled resonators," IEEE Transactions on Microwave Theory and Techniques, 63, no. 6, pp. 1843-1853, June 2015.

      Abstract: A simple strategy is proposed to design differential-mode bandpass filters with good common-mode (CM) rejection using simple resonators. Specifically, the CM rejection is enhanced by using conventional open-loop resonators as well as folded stepped-impedance resonators without the addition of printed or lumped elements along the symmetry plane of the filter or the use of defected ground solutions. The novelty of the present proposal is that a good CM rejection is achieved by the use of magnetic coupling instead of the more commonly employed electrical coupling. Magnetic coupling inherently yields poorer CM transmission as requested by good differential filters. The resonators, due to their geometrical simplicity, can easily be cascaded to implement high-order filters. The use of simple geometries also simplifies the design methodology and makes final tuning based on electromagnetic simulation simpler or unnecessary.

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• INTERNATIONAL CONFERENCE PAPERS/ABSTRACTS
  1. F. Mesa, F. Medina, R. Rodríguez-Berral, "On the circuit modeling of extraordinary-transmission phenomena," (INVITED TALK), 3rd Mediterranean Conference on Nanophotonics, Medinano-3 (Belgrade, Serbia), 18-19 October 2010.

  2. J.M. Algarín, M.J. Freire, R. Marqués, "Analysis of the transfer function of split-ring metamarial slabs," 4th Young Scientist Meeting on Metamaterials, (Valencia, Spain), p. 12 del libro de actas (3 páginas), 14-16 Febrero 2011.

  3. V. Delgado, R. Marqués, L. Jelinek, "Extraordinary transmission in semitransparent screens with a periodic distribution of defects," 4th Young Scientist Meeting on Metamaterials, (Valencia, Spain), p. 16 del libro de actas (3 páginas), 14-16 Febrero 2011.

  4. R. Rodríguez-Berral, F. Medina, F. Mesa, "Analytical Modeling of Extraordinary Transmission in the Presence of Dielectric Slabs," (INVITED TALK), Progress in Electromagnetic Research Symposium, PIERS 2011 (Marrakesh, Morocco), 20-23 March 2011.

  5. A. L. Fructos, R.R. Boix, F. Mesa, "A contribution to the efficient computation of multilayered periodic Green's functions," 5th European Conference on Antennas and Propagation, EuCAP 2011 (ISBN: 978-1-4577-0250-1), (Rome, Italy), pp. 2471-2474, 11-15 April 2011.

  6. M.A. López-Terrones, J.M. Algarín, M.J. Freire, P.M. Jakob, V.C. Behr, R. Marqués, "Metamaterial Media for MRI Applications," 19th Annual Meeting of the ISMRM (International Society of Magnetic Resonance in Medicine), (Montreal, Canada), p. 636, 6-13 May 2011.

  7. M.A. López-Terrones, G. Lykowsky, J.M. Algarín, M.J. Freire, M.C. Velázquez-Ahumada, P.M. Jakob, R. Marqués, "A Loop Coil Design Based on the Broadside-Coupled Split Ring Resonator at 7T," 19th Annual Meeting of the ISMRM (International Society of Magnetic Resonance in Medicine), (Montreal, Canada), p. 5416, 6-13 May 2011.

  8. M. García-Vigueras, F. Mesa, R. Rodríguez-Berral, F. Medina, L. Gómez-Tornero, "Equivalent Circuits for Conventional and Extraordinary Reflection in Dipole Arrays," 2011 IEEE International Microwave Symposium, IMS 2011 (ISBN: 978-1-61284-757-3), (Anaheim, CA, USA),5-10 June 2011.

  9. C. S. R. Kaipa, A. Yakovlev, F. Medina, F. Mesa, Y. R. Padooru, "Sub-wavelength Transmission Through Stacked Two-dimensional Metallic Patches: A Circuit Model Perspective," 2011 IEEE-AP-URSI/USNC Symposium (ISBN: 978-1-4244-9561-0), (Spokane, WA, USA), 3-8 July 2011.

  10. G. Bigel, F. Medina, F. Mesa, R. Rodríguez-Berral, "Transmission of EM waves through arrays of stepped subwavelength slits," 2011 IEEE-AP-URSI/USNC Symposium (ISBN: 978-1-4244-9561-0), (Spokane, WA, USA), 3-8 July 2011.

  11. F. Medina, F. Mesa, D. Skigin, "Analytical modeling of compound metallic reflection gratings," 2011 IEEE-AP-URSI/USNC Symposium (ISBN: 978-1-4244-9561-0), (Spokane, WA, USA), 3-8 July 2011.

  12. Y. R. Padooru, A. B. Yakovlev, C. S. R. Kaipa, F. Medina, F. Mesa, "Multi-band High-Impedance Surface Absorbers with a Single Resistive Sheet: Circuit Theory Model," 2011 IEEE-AP-URSI/USNC Symposium (ISBN: 978-1-4244-9561-0), (Spokane, WA, USA), pp. 2264-2267, 3-8 July 2011.

  13. A. L. Fructos, R. R. Boix, F. Mesa, "New Developments for the Efficient Computation of Multilayered Periodic Green's Functions," 2011 IEEE-AP-URSI/USNC Symposium (ISBN: 978-1-4244-9561-0), (Spokane, WA, USA), pp. 2264-2267, 3-8 July 2011.

  14. J. Bernal, F. Mesa, D. R. Jackson, S. Saucedo, M.C. Velázquez-Ahumada, "Measurement of Spurious Interference Effects Due to the Excitation of Low Frequency Leaky Modes in a Covered Microstrip," XXX URSI General Assembly and Scientific Symposium of International Union of Radio Science (ISBN: 978-1-4244-5118-0), (Istanbul, Turkey), 4 pages CD, 13-20 August 2011.

  15. El-Mokhtar Hamham, F. Mesa, F. Medina, M. Khalladi, "Efficient quasi-TEM approach for the calculation of conductor loss of multilayer microstrip lines," Proc. of the 11th Mediterranean Microwave Symposium, (Hammamet, Túnez), 8-10 September 2011.

  16. F. Mesa, F. Medina, M. García-Vigueras, R. Rodríguez-Berral, J. L. Gómez-Tornero, "Circuit Approach for a General Study of Frequency Selective Surfaces," (INVITED TALK), 2011 International Conference on Electromagnetics in Advanced Applications (ICEAA'11) (ISBN: 978-1-61284-978-2), (Torino, Italy), pp. 122-125, 12-16 September 2011.

  17. J.M. Algarín Guisado, M.A. López-Terrones, M.J. Freire Rosales, R. Marqués Sillero, "SNR improvement of MRI coils by means of metamaterial lenses," 28th Annual Scientific Meeting of the ESMRMB (European Society for Magnetic Resonance in Medicine and Biology), (Leipzig, Alemania), pp. 165-166, póster 232, 6-8 Octubre 2011.

  18. M.A. López-Terrones, F.M. Meise, J.M. Algarín, M.J. Freire, P.M. Jakob, M. Bock, R. Marqués, "A broadside-coupled-loop coil at 7T whole body system," 28th Annual Scientific Meeting of the ESMRMB (European Society for Magnetic Resonance in Medicine and Biology) (Leipzig, Alemania), p. 421, poster 600, 6-8 Octubre 2011.

  19. F. Medina, G. Bigel, F. Mesa, R. Rodríguez-Berral, "Analytical modeling of structured 1D diffraction gratings using a microwave engineering approach," Proc. of the 41st European Microwave Conference (ISBN: 978-2-87487-022-4), (Manchester, UK), pp. 814-817, 9-14 October 2011.

  20. A. Fernández-Prieto, J. Martel, J. S. Hong, F. Medina, S. Qian and F. Mesa, "Differential transmission line for common-mode suppression using double side MIC technology," Proc. of the 41st European Microwave Conference (ISBN: 978-2-87487-022-4), (Manchester, UK), pp. 631-634, 9-14 October 2011.

  21. J. Naqui, M. Durán-Sindreu, A. Fernández-Prieto, F. Mesa, F. Medina, F. Martin, "Differential transmission lines loaded with split ring resonators (SRRs) and complementary split ring resonators (CSRRs)," (INVITED TALK), Fifth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, Metamaterials 2011 (ISBN: 978-952-67611-0-7), (Barcelona, Spain), pp. 304-306, 10-15 October 2011.

  22. A. Fernández-Prieto, J. Martel, F. Medina, F. Mesa, S. Qian, J.-S. Hong "Microstrip/CPW differential lines for common-mode suppression," Fifth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, Metamaterials 2011 (ISBN: 978-952-67611-0-7), (Barcelona, Spain), pp. 313-315, 10-15 October 2011.

  23. F. Medina, G. Bigel, F. Mesa, R. Rodríguez-Berral, "Closed-form analysis of electrically thick diffraction gratings with internal structure," Fifth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, Metamaterials 2011 (ISBN: 978-952-67611-0-7), (Barcelona, Spain), pp. 733-735, 10-15 October 2011.

  24. R. Rodríguez-Berral, F. Mesa, F. Medina, "Analytical model for periodic arrays of slits/strips printed on dielectric slabs: TE and TM polarizations," Fifth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, Metamaterials 2011 (ISBN: 978-952-67611-0-7), (Barcelona, Spain), pp. 739-741, 10-15 October 2011.

  25. M.J. Freire, M.A. López, J.M. Algarín, V.C. Behr, P.M. Jakob, R. Marqués, "Zero-permeability nonlinear split-ring metamaterials for magnetic resonance imaging applications," Fifth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, Metamaterials 2011, (Barcelona, Spain), pp. 80-82, 10-15 October 2011.

  26. F. Medina, F. Mesa, R. Rodríguez-Berral, "Advances on the analytical modeling of 1D and 2D metallic gratings," (INVITED TALK, PLENARY SESSION), 2nd Conference on Waves in Science and Engineering, WISE 2011, (Mexico City, Mexico), 7-11 noviembre 2011.

  27. Y. R. Padooru, A. B. Yakovlev, C. S. R. Kaipa, G. W. Hanson, F. Medina, F. Mesa, A. W. Glisson, "Absorbing boundary conditions and the homogenization model for multilayered wire media," 2012 URSI National Radio Science Meeting, (Boulder, CO, USA) 4-7 enero 2012.

  28. R. Rodríguez-Berral, F. Mesa, F. Medina, "Analytical model for TM scattering of 1-D narrow slit gratings loaded with dielectric slabs," 6th European Conference on Antennas and Propagation, EuCAP 2012, (ISBN: 978-1-4577-0919-7) (Praga, Chezc Republic), pp. 3089-3093, 26-30 March 2012.

  29. J. M. Algarín-Guisado, M. A. López-Terrones, M. J. Freire, R. Marqués, "Split-ring metamaterials for MRI applications," 3rd International Conference on Metamaterials, Photonic Crystals and Plasmonics, META 2012, (Paris, France), 19-22 abril abril 2012.

  30. M. A. López-Terrones, J. M. Algarín-Guisado, M. J. Freire, F. A. Breuer, R. Marqués, "Application of magneto-inductive metamaterial lenses in parallel imaging," ISMRM 2012, 20th Annual Meeting, (Melbourne, Australia), 5-11 May 2012.

  31. F. Medina, F. Mesa, R. Rodríguez-Berral, (invited contribution, focused session), "Analytical modelling of microwave/millimeter wave 1D and 2D gratings and fishnets," 4th International Conference SMART, Materials, Structures, Systems, CIMTEC 2012, Focused Session on Metamaterials, (Montecatini Terme, Italy), 10-14 June 2012.

  32. C.S.R. Kaipa, A.B. Yakovlev, G.W. Hanson, Y.R. Padooru, F. Medina, F. Mesa, "Low-Terahertz transmissivity with a graphene-dielectric micro-structure," 2012 IEEE MTT-S International Microwave Symposium, (ISBN: 978-1-4673-1088-8/12) (Montreal, Canada), 3 pp., 17-22 June 2012.

  33. R. Rodríguez-Berral, F. Mesa, F. Medina, "Fully analytical circuit-like approach for the TE scattering by narrow-slit printed gratings," 2012 IEEE MTT-S International Microwave Symposium, (ISBN: 978-1-4673-1088-8/12) (Montreal, Canada), 3 pp., 17-22 June 2012.

  34. C. S. R. Kaipa, A. B. Yakovlev, G. W. Hanson, Y. R. Padooru, F. Medina, F. Mesa, "Low-Terahertz transmissivity and broadband planar filters using graphene-dielectric stack," 2012 IEEE AP-S International Symp. on Antennas and Propagat. and URSI/USNC North America Radio Science Meeting, (Chicago, IL, USA), abstract, 8-14 July 2012.

  35. Y. R. Padooru, A. B. Yakovlev, C. S. R. Kaipa, G. W. Hanson, F. Medina, F. Mesa, A. W. Glisson, "Generalized additional boundary conditions and analytical model for multilayered mushroom-type wideband absorbers," 2012 IEEE AP-S International Symp. on Antennas and Propagat. and URSI/USNC North America Radio Science Meeting, (ISBN: 978-1-4673-0462-7) (Chicago, IL, USA), 2 pp., 8-14 July 2012.

  36. J. Bernal, F. Mesa, D.R. Jackson, "Crosstalk and low frequency radiation in a coupled microstrip line with a top cover," IEEE International Symposium on Electromagnetic Compatibility, (ISBN: 978-1-4673-2061-0) (Pittsburgh, Pa, USA), pp. 12-17, 6-10 August 2012.

  37. F. Medina, F. Mesa, R. Rodríguez-Berral, "Efficient circuit models for extraordinary transmission structures," (invited paper), Metamaterials 2012: The Sixth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, (ISBN: 978-952-67611-2-1) (Saint Petersburg, Russia), pp. 59-61, 17-20 September 2012.

  38. R. Marqués, V. Delgado, J. D. Baena, J. D. Ortiz, "Complementarity and Babinet principle in optical nano-circuits and metamaterials," Metamaterials 2012: The Sixth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, (ISBN: 978-952-67611-2-1) (Saint Petersburg, Russia), pp. 737-739, 17-20 September 2012.

  39. M. J. Freire, M. A. López, J. M. Algarín, F. Breuer, R. Marqués, "Magnetoinductive lenses for reduction of correlated noise in parallel magnetic resonance imaging," Metamaterials 2012: The Sixth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, (ISBN: 978-952-67611-2-1) (Saint Petersburg, Russia), pp. 17-19, 17-20 September 2012.

  40. M. Lapine, L. Jelinek, R. Marqués, "Mesoscopic surface effects in finite metamaterial samples," Metamaterials 2012: The Sixth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, (ISBN: 978-952-67611-2-1) (Saint Petersburg, Russia), pp. 577-579, 17-20 September 2012.

  41. V. Delgado, R. Marqués, L. Jelinek, "Surface impedance and coupled-wave model for extraordinary optical transmission through realistic metallic screens," Metamaterials 2012: The Sixth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, (ISBN: 978-952-67611-2-1) (Saint Petersburg, Russia), pp. 50-52, 17-20 September 2012.

  42. M. A. López, M. During, C. Caparrós, M. J. Freire, R. Marqués, "A Dedicated 4-Channel Flexible Array Coil for Ocular Imaging," ESMRMB 2012, 29th Annual Scientific Meeting, (Lisbon, Portugal), 4-6 October 2012.

  43. M. A. López-Terrones, J. M. Algarín, M. J. Freire, F. A. Breuer, R. Marqués, "Analysis of Array Decoupling Mechanisms Using Magneto-Inductive Metamaterial Lenses at 1.5 T," ESMRMB 2012, 29th Annual Scientific Meeting, (Lisbon, Portugal), 4-6 October 2012.

  44. F. Medina, R. Rodríguez-Berral, F. Mesa, "Circuit Model for Metallic Gratings With Tapered and Stepped Slits," 42nd European Microwave Conference, EuMC 2012, (ISBN: 978-2-87487-027-9) (Amsterdam, The Netherlands), pp. 1225-1228, 29-1 Oct.-Nov. 2012

  45. F. Mesa, R. Rodríguez-Berral, F. Medina, M. García-Vigueras, (invited talk) "Enhanced circuit modeling of metasurfaces," META-13, The 4th International Conference on Metamaterials, Photonic Crystals and Plasmonics, (Sharjah, United Arab Emirates), 18-22 March 2013.

  46. R. Florencio, R. R. Boix, J. A. Encinar, "Improvements in the MoM analysis of 2-D planar multilayered periodic structures," 7th European Conference on Antennas and Propagation, EuCAP 2013, (Goteborg, Suecia), pp. 612-613, 8-12 April 2013 (E-ISBN : 978-88-907018-1-8, Print ISBN: 978-1-4673-2187-7).

  47. R. Florencio, R. R. Boix, J. A. Encinar, "Improved MoM analysis of periodic multilayered structures. Applications to the analysis and design of reflectarray antennas," IX Iberian Meeting on Computational Electromagnetics, (Denia, Spain), 4 pages, 14-17 May 2013.

  48. R. Rodríguez-Berral, F. Mesa, F. Medina, M. García-Vigueras, "Analytical wideband model for dielectric loaded 1D and 2D metallic periodic structures," IX Iberian Meeting on Computational Electromagnetics, (Denia, Spain), 4 pages, 14-17 May 2013.

  49. R. Rodríguez-Berral, F. Mesa, F. Medina, M. García-Vigueras, "Analytical Circuit Model for Dipole Frequency-Selective Surfaces," 2013 IEEE International Microwave Symposium, (Seattle, WA, USA), 4 pages, 2-7 June 2013 (ISBN: 978-1-4673-2141-9/13).

  50. Y.R. Padooru, A.B. Yakovlev, C.S.R. Kaipa, G.W. Hanson, F. Medina, F. Mesa, "Dual capacitive-inductive nature of graphene metasurface: transmission characteristics at low-terahertz frequencies," 2013 IEEE International Symposium on Antennas and Propagation, (Orlando, FL, USA), pp. 1598-1599 (ISBN: 978-1-4673-5317-5/13), 7-13 July 2013.

  51. J.D. Ortiz, J.D. Baena, V.Losada, F.Medina, "Metasurfaces made of transmission Lines: a way to spatial filtering," 2013 IEEE International Symposium on Antennas and Propagation, (Orlando, FL, USA), 7-13 July 2013. (ISBN: 978-1-4673-5317-5/13).

  52. J. Bernal, F. Mesa, D.R. Jackson, "Differential signaling in covered coupled microstrip lines," International Symposium on Electromagnetic Compatibility, EMC Europe 2013, (Brujas, Bélgica), pp. 288-293, 2-6 September 2013. (ISBN: 978-1-4673-4980-2).

  53. J. Naqui, M. Duran-Sindreu, F. Martin, A. Fernandez-Prieto, F. Mesa, F. Medina, "Complex modes in periodic transmission lines based on split rings," (invited paper), 15th International Conference on Electromagnetics in Advanced Applications, ICEAA 2013, (Torino, Italy), pp. 863-866 (ISBN: 978-1-4673-5705-0), 9-14 de September 2013.

  54. F. Medina, F. Mesa, R. Rodríguez-Berral, M. García-Vigueras, "Analytical circuit modeling of 1D and 2D planar metal gratings embedded in stratified dielectric structures," (invited paper), 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, Metamaterials 2013, (Burdeos, Francia), 15-19 de September 2013 (ISBN: 978-952-67611-5-2).

  55. F. Medina, "Accurate circuit modeling of extraordinary transmission and FSS structures," (invited paper, plenary session), 1st Workshop on Metamaterials and Photonic Crystals, MEPHOC 2013, (Armenia, Colombia), 30-Sept. a 4-Oct. 2013.

  56. J.D. Ortiz, V. Losada, J.D. Baena, F. Medina, "Spatial filtering by metasurfaces made of chains of interconnected SRRs and CSRRs,'' 1st Workshop on Metamaterials and Photonic Crystals, MEPHOC 2013, (Armenia, Colombia), pp. 29-30, 30-Sept. a 4-Oct. 2013.

  57. J.D. Ortiz, J.D. Baena, V. Losada, F. Medina, R. Marqués, J.L. Araque, "Self-complementary metasurfaces," 1st Workshop on Metamaterials and Photonic Crystals, MEPHOC 2013, (Armenia, Colombia), p. 75, 30-Sept. a 4-Oct. 2013.

  58. F. Medina, "Accurate circuit modeling of extraordinary transmission and FSS structures," (short course, invited), 1st Workshop on Metamaterials and Photonic Crystals, MEPHOC 2013, (Armenia, Colombia), 30-Sept. a 4-Oct. 2013.

  59. M. García-Vigueras, F. Mesa, R. Rodríguez-Berral, F. Medina, J.R. Mosig, "Efficient numerically-assisted modelling of grounded arrays of printed patches," (invited paper), 2013 International Symposium on Antennas and Propagation (ISAP), (Nanjing, China), 23-25 October 2013.

  60. M. García-Vigueras, J. R. Mosig, F. Mesa, R. Rodríguez-Berral, F. Medina, "Closed-form expressions for modeling diffraction at printed dipole-based FSS," (Best Paper Award), IEEE 2013 International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications (MAPE 2013), (Chengdu, China), pp. 500-503, 29-31 October 2013.

  61. M. García-Vigueras, F. Mesa, R. Rodríguez-Berral, F. Medina, J. R. Mosig, "Efficient network representation of grounded patch-based FSS," The 8th European Conference on Antennas and Propagation, EuCAP 2014, (The Hague, The Netherlands), pp. 2334-2337, 6-11 April 2014.

  62. R. Rodríguez-Berral, F. Mesa, F. Medina, "Circuit Model for Patch/Slot-Based Frequency Selective Surfaces Under Conical Incidence," The 8th European Conference on Antennas and Propagation, EuCAP 2014, (The Hague, The Netherlands), pp. 1714-1718, 6-11 April 2014.

  63. R. Rodríguez-Berral, F. Mesa, F. Medina, "Analytical circuit model for stacked slit gratings," IEEE International Microwave Symposium, IMS 2014, (Tampa, FL, USA) 1-6 June 2014. (3 pages in ISBN: 978 1-4799-3869-8/14, IEEE Xplore).

  64. F. Mesa, R. Rodríguez-Berral, F. Medina, "Recent progress on FSS and extraordinary transmission analytical modeling," (invited paper), 8th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials 2014), (Copenhagen, Denmark), pp. 202-204, 25-30 August 2014.

  65. J. D. Ortiz, J. P. del Risco, J. D. Baena, V. Losada, F. Medina, J. L. Araque, "Metasurfaces for Angular Filtering and Beam Scanning," 8th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials 2014), (Copenhagen, Denmark), pp. 34-36, 25-30 August 2014.

  66. M. García-Vigueras, F. Mesa, R. Rodríguez-Berral, F. Medina, J. R. Mosig, "Insightful circuit modeling of FSS with arbitrary scatterers," The 9th European Conference on Antennas and Propagation, EuCAP 2015, (Lisbon, Portugal), 13-17 April 2015, (4 pages in ISBN: 978-8-8907-0182-5).

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• NATIONAL CONFERENCE PAPERS/ABSTRACTS
  1. El-Mokhtar Hamham, F. Mesa, F. Medina, M. Khalladi, "Una aproximación cuasi-TEM para el cálculo eficiente de las pérdidas en el conductor en líneas microtiras simples y acopladas multicapa," XXVI Symposium Nacional de URSI, (Leganés, Madrid), 7-9 September 2011. (ISBN: 978-84-933934-4-1 (abstracts); 978-84-933934-5-8 (CD-ROM); in Spanish).

  2. R. Rodríguez-Berral, F. Medina, F. Mesa, M. García-Vigueras, "Modelo analítico para rejillas de difracción metálicas cargadas con dieléctricos," XXVI Symposium Nacional de URSI, (Leganés, Madrid), 7-9 September 2011. (ISBN: 978-84-933934-4-1 (abstracts); 978-84-933934-5-8 (CD-ROM); in Spanish).

  3. M. García-Vigueras, F. Mesa, F. Medina, R. Rodríguez-Berral, J.L. Gómez-Tornero, "Circuitos equivalentes para el modelado de la reflexión convencional y extraordinaria en arrays de dipolos," XXVI Symposium Nacional de URSI, (Leganés, Madrid), 7-9 September 2011. (ISBN: 978-84-933934-4-1 (abstracts); 978-84-933934-5-8 (CD-ROM); in Spanish).

  4. Safae El Amrani, R. Rodríguez Berral, F. Mesa, M. Boussouis, "Estudio del espectro modal excitado en una guía coplanar convencional," XXVI Symposium Nacional de URSI, (Leganés, Madrid), 7-9 September 2011. (ISBN: 978-84-933934-4-1 (abstracts); 978-84-933934-5-8 (CD-ROM); in Spanish).

  5. A. Fernández-Prieto, J. Martel, J.-S. Hong, F. Medina, S. Qian, F. Mesa, "Líneas diferenciales para supresión de modo común usando tecnología MIC de doble cara," XXVI Symposium Nacional de URSI, (Leganés, Madrid), 7-9 September 2011. (ISBN: 978-84-933934-4-1 (abstracts); 978-84-933934-5-8 (CD-ROM); in Spanish).

  6. A. Fernández-Prieto, M.C. Velázquez-Ahumada,, J. Martel, F. Medina, F. Mesa, "Nuevas Aportaciones al Diseño de Filtros Microtira y Líneas Diferenciales del Grupo de Microondas de la Universidad de Sevilla," (4 pages), VIII Encuentro Ibérico de Electromagnetismo Computacional, (Sesimbra, Portugal), 2-4 November 2011.

  7. R. Rodríguez-Berral, F. Medina, F. Mesa, M. García-Vigueras, J. L. López-Tornero, "Recent advances in circuit modeling of the transmission of electromagnetic waves through periodic screens," (4 pages), VIII Encuentro Ibérico de Electromagnetismo Computacional, (Sesimbra, Portugal), 2-4 November 2011.

  8. F. Medina, "Transmisión Extraordinaria vista por un Ingeniero de Microondas," XXVII Symposium Nacional de URSI, (CONFERENCIA PLENARIA), Actas del congreso en CD-ROM (2 páginas, ISBN: 978-84-695-4327-6), (Elche, Alicante), 12-14 September 2012.

  9. R. Rodríguez-Berral, F. Mesa, F. Medina, "Analytical equivalent circuit for slit gratings in dielectric-coated thick metallic screens," XXVII Symposium Nacional de URSI, Actas del congreso en CD-ROM (2 páginas, ISBN: 978-84-695-4327-6), (Elche, Alicante), 12-14 September 2012.

  10. R. Rodríguez-Berral, F. Medina, F. Mesa, "Analytical circuit model for metal gratings with nonuniform slits," XXVII Symposium Nacional de URSI, Actas del congreso en CD-ROM (2 páginas, ISBN: 978-84-695-4327-6), (Elche, Alicante), 12-14 September 2012.

  11. C. Molero, R. Rodríguez-Berral, F. Medina, F. Mesa, "Analytical circuit model for coupled strip/slit gratings printed on dielectric slabs," XXVII Symposium Nacional de URSI, Actas del congreso en CD-ROM (2 páginas, ISBN: 978-84-695-4327-6), (Elche, Alicante), 12-14 September 2012.

  12. C. Molero, R. Rodríguez-Berral, F. Mesa, F. Medina, "Analytical circuit model for 1-D periodic T-shaped corrugated surfaces," XXVIII Symposium Nacional de URSI, Actas del congreso en CD-ROM (4 pages, ISBN: 978-84-941537-1-6), Santiago de Compostela, 11-13 September 2013. Accesit Mejor Trabajo Investigadores Jóvenes.

  13. R. Rodríguez-Berral, F. Mesa, F. Medina, M. García-Vigueras, "Modelo de circuito analítico para SSF de dipolos," XXVIII Symposium Nacional de URSI, Actas del congreso en CD-ROM (4 pages, ISBN: 978-84-941537-1-6), Santiago de Compostela, 11-13 September 2013. Sesión especial homenaje al Prof. Eduardo Moreno.

  14. C. Molero, R. Rodríguez-Berral, F. Mesa, F. Medina, A. Yakovlev, "High-frequency equivalent circuit for finite-stacked slit gratings," XXIX Symposium Nacional de URSI, Actas del congreso en CD-ROM (4 pages, ISBN: 978-84-9048-264-3), Valencia, 3-5 septiembre 2014.

  15. A. Fernández-Prieto, J. Martel, F. Medina, F. Mesa, "Nuevo filtro diferencial compacto basado en FSIR's con plano de masa modificado para supresión del modo común," XXIX Symposium Nacional de URSI, Actas del congreso en CD-ROM (4 pages, ISBN: 978-84-9048-264-3), Valencia, 3-5 septiembre 2014.

  16. C. Molero, R. Rodríguez-Berral, F. Mesa, F. Medina, "Wideband analytical circuit model for 1-D compound gratings," XXIX Symposium Nacional de URSI, Actas del congreso en CD-ROM (4 pages, ISBN: 978-84-9048-264-3), Valencia, 3-5 septiembre 2014. Accesit Mejor Trabajo Investigadores Jóvenes.

  17. R. Rodríguez-Berral, F. Mesa, F. Medina, "Circuito equivalente multimodo para arrays periódicos de parches o ranuras rectangulares," XXIX Symposium Nacional de URSI, Actas del congreso en CD-ROM (4 pages, ISBN: 978-84-9048-264-3), Valencia, 3-5 septiembre 2014.

  18. J. M. Algarín, M. Freire, F. Breuer, V. C. Behr, "Metamaterial magnetoinductive lens performance as a function of field strength and acceleration factor," XXIX Symposium Nacional de URSI, Actas del congreso en CD-ROM (4 pages, ISBN: 978-84-9048-264-3), Valencia, 3-5 septiembre 2014.

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• PATENTS

  Inventores: F. Medina (US), A. Fernández-Prieto (US), F. Mesa, F. Martín (UAB), M. Durán-Sindreu, (UAB), J. Naqui (UAB).
  Título: "Dispositivo de líneas de transmisión diferenciales con supresión de modo común".
  No. de solicitud: P201100616   País de prioridad: España   Fecha de prioridad: 1 de June de 2011 .
  Entidades titulares: Universitat Autónoma de Barcelona (UAB) y Universidad de Sevilla (US).

  Inventores: F. Medina (US), A. Fernández-Prieto (US), F. Mesa, F. Martín (UAB), M. Durán-Sindreu, (UAB), J. Naqui (UAB).
  Título: "Device comprising differential transmission lines with common-mode suppression".
  No. de solicitud: PCT/ES2012/000150   País de prioridad: Tratado PCT   Fecha de prioridad: 3 de May 2012.
  Entidades titulares: Universitat Autónoma de Barcelona (UAB) y Universidad de Sevilla (US).

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  BIBLIOMETRIC STATISTICS

  

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