Suchergebnisse

This communication presents a novel diode switchable chiral metamaterial structure that manipulates the polarization in different ways depending on the active bias lines. Three different bias states that provide three totally different behaviors have been considered: polarization rotator, circular polarization converter and linear to circular converter. ; This work has been partially supported by the Spanish Government MINECO through the ERDF co-funded Research Projects TEC2014-55463-C3-1-P, TEC2014-55463-C3-2-P and TEC2014-55463-C3-3-P.

Negative refraction has many potential applications in the information and communications technology field. However, the high losses of most negative refraction materials prevent the use of this novel property in the implementation of practical devices in the HF range. In an attempt to overcome this inconvenience, we present two gammadion-fishnet chiral metamaterial structures, constituted by the combination of a lossy chiral metamaterial and different fishnet structures. The electromagnetic characterization of the proposed metamaterials provides a larger bandwidth with negative refraction as well as lower losses when compared with the initial structures. The results were obtained by using both numerical and experimental data, which support our designs. ; This work has been partially supported by the Spanish Government MINECO through the ERDF co-funded Research Projects TEC2014-55463-C3-1-P and TEC2014-55463-C3-3-P, PGC2018-098350-B-C21 and PGC2018-098350-B-C22.

In this work a composed chiral metamaterial structure constituted by the combination of a composite chiral metamaterial and a modified fishnet structure is presented and numerically analyzed. This new fishnet-like chiral metamaterial features two wide frequency bands wherein the refractive indices are negative and exhibits lower losses than its constituents do. ; This work has been partially supported by the Spanish Government MINECO through the ERDF co-funded Research Projects TEC2014-55463-C3-1-P and TEC2014-55463-C3-3-P.

In this communication the authors present a novel chiral metamaterial structure formed by planar omega particles These omega particles, arranged in conjugated pairs, present high optical activity. Thanks to the high values of chirality, the structure provides negative refractive index with high figure of merit. ; This work has been supported by the Spanish Government MINECO through the Research Projects TEC2014-55463-C3-1-P, TEC2014-55463-C3-3-P and by the European Commission (ERDF).

Green integral formulation of the boundary value problem in chirowaveguides with translational symmetry and the application to the rectangular case are presented in this paper. The Green equations for the two eigenmodes in unbounded chiral media, i.e. right and left circularly polarized waves, are formulated in terms of the Hankel functions. By splitting the waveguide contour into a finite number of intervals, the equations are discretized and a homogeneous system of equations can be obtained. The number of unknowns is reduced to the half by applying the relations between the longitudinal components and their normal derivatives at the metallic contours. The method has been used for modeling the rectangular waveguide and the dispersion diagram and the field structure for some propagation modes are presented. ; This work was supported by the Spanish Government (Research Projects TEC2014-55463-C3-1-P and TEC2014-55463-C3-2-P) and by the European Commission (ERDF).

In the last years, the Research Groups on Computational Electromagnetics (GrECo), from the University of Valladolid, and on Applied Electromagnetics, from the University of Murcia, have been working together in the design, fabrication, modelling and measuring new chiral media to be used in the microwave frequency range. This has been done in the frame of Research Projects funded by Spanish Government and, as a result, chiral media based in metallic inclusions in a host dielectric have been performed. The latest realizations, until now, use metallic "crank-like" inclusions assembled in various geometries to avoid undesired effects such as anisotropy, non-reciprocity and polarization filter effects. ; Ingeniería, Industria y Construcción

A new free-wave experimental method for chiral media characterization is presented. The setup is based on a pair of dual horn antennas and a diplexer 90◦ phase shifter, which allows to produce both circularly and linearly polarized waves and to measure the co- and cross-polar components of the transmission and reflection coefficients of a chiral slab under normal illumination. Then, six experimental measurements are available to retrieve three constitutive parameters. Furthermore, by including the reflection coefficient of the backed metal sample an over determined system of equations is obtained, which leads to increase the accuracy of the material characterization. ; This work was supported by the Spanish Government (Projects TEC2014-55463-C3-1-P and TEC2014-55463-C3-2-P) and by the European Commission (ERDF). The authors thank C. Arévalo for helping with the paper edition.

A planar complementary metamaterial, as well as its corresponding inverse structure, has been designed and characterized. Numerical results (using commercial software) are presented here. The structure shows a giant gyrotropy (chirality) as well as very low losses. ; This work has been supported by the Spanish Government (MINECO) through the Research Projects TEC2014-55463-C3-1-P, TEC2014-55463-C3-2-P, and TEC2014-55463-C3-3-P and also by the European Commission (ERDF).

Owing to the large size of the dataset, scientists interested in it are encouraged to contact the authors directly. The atmospheric properties used in the present study have been taken from the Mars Climate Database http://www-mars.lmd.jussieu.fr/. ; Schumann resonances are standing waves that oscillate in the electromagnetic cavity formed between the conducting lower ionosphere and the surface of the planet. They have been measured in situ only on Earth and Titan, although they are believed to exist on other planets like Mars. We report numerical simulations of the Martian electromagnetic cavity, accounting for the day-night asymmetry and different dust scenarios. It has been found that the resonances are more energetic on the nightside, the first resonance is expected to be 9–14 Hz depending on the dust activity and to have low quality factors (Q ≃ 2). This work serves as an input for the upcoming Exomars surface platform (launch 2020), who will attempt to measure them for the first time. ; This work was supported by the Ministerio de Economía y Competitividad of Spain under the project with reference FIS2013-44975-P, cofinanced with FEDER funds of the European Union. S.T.R. holds an ESA research fellowship and acknowledges support from the ESA science faculty of the European Space Astronomy Centre (ESAC).