Medio EBG basado en estructuras simples en forma de L

In the present work a study of the prohibited frequency bands produce in a microstrip line when introducing inclusions of metallic elements with "L" shaped has been carried out. The inclusion of these structures on both sides of the transmission line causes the appearance of a broad bandgap within the region of frequencies of interest. It has been found that the existence of more than one row on either side of the line does not significantly modify the response. In order to extend the bandgap and make it more uniform, several modifications to the parameters and structure distribution has been proposed. It has been found that both the arrangement of a thicker dielectric sheet and the structure tapering can improve the response. Furthermore, they produce a decreasing of the fields and, therefore, unwanted radiation in nearby elements can be reduced.Ingeniería, Industria y Construcció

Large Electromagnetic Activity Metamaterial Composed of Five-Segment Cranks

Producción CientíficaA new chiral material composed of a two-dimensional lattice of five-segment cranks, with the same handedness is experimentally and numerically studied. The sample, formed by a single layer of such structures, exhibits huge electromagnetic activity and a negative refraction index for linearly polarized waves. Both the chirality parameter and the bandwidth with the negative refraction index are larger than those observed in chiral media composed of three-segment cranks. The material also shows pronounced electromagnetic activity (larger than 500 per wavelength). This observed behaviour is attributed to the fact that the five-segment configuration enhances the electromagnetic coupling compared with the three-segment configuration.2020-01-012020-01-01Ministerio de Economía, Industria y Competitividad and the European Commission (ERDF)(Projects TEC2014-55463-C3-1- P and TEC2014-55463-C3-3-P

Design of electromagnetic band gap media based on crank-like chiral structures

A new EBG (Electromagnetic Band Gap) structure with chiral crank elements is presented and its effects on the electric field propagation along a microstrip line are analysed and compared with the effects produced by mushroom-type inclusions. Chiral crank inclusions are distributed along both sides of the strip and the corresponding results are compared with those obtained by other elements commonly used to create EBG media, mushroom-type structures. A single row of high chirality structures on both sides of a transmission line produces a band gap with a wider bandwidth than that obtained by the inclusion of other elements commonly used to create EBG media, such as mushroom-type structures. Unlike what happen with mushroomtype inclusions, more rows of chiral elements do not change significantly the central frequency and bandwidth of the band gap. The proposed structure works in X-Band (8.2-12.4 GHz) and it is easily adaptable to other frequencies by changing the size of the crank inclusions. Several samples have been made in FR-4 printed circuit board and a good agreement has been found between numerical analysis and experimental measurements.This work has been supported by the Ministerio de Economía y Competitividad of Spain (ERDF co-funded Research Projects PGC2018-098350-B-C21 and PGC2018-098350-B-C22

Estudio de medios EBG basados en estructuras metálicas en forma de paralelepípedo

In this paper microstrip lines with periodic metallic structures on both sides have been studied. The basic unit cell is a parallelepiped with different metallization at the edges. The effects on the transmission in a standard microstrip line have been analysed by using both experimental and simulation (CST Microwave Studio®) techniques, obtaining an EBG behaviour similar to the one obtained with mushroom-like structures. The proposed structures present advantages in band gap size. Furthermore, the response does not dependent on the number of rows at the sides of the microstrip line.Ingeniería, Industria y Construcció

Estudio de doble lámina con estructuras quirales de cuatro manivelas bajo incidencia normal

A double plate with chiral structures based on three segment cranks is analysed for normal incidence and lineal polarization. Each structure is made with four three segment crank arranging a rectangular parallelepiped. These structures are distributed in a periodic configuration in each sheet, being the respective unit cells perfectly lined up. The response depends on spacing between plates. Interesting results are obtained for small spacing: the chiral behaviour depends on the spacing then the double sheet system can be used as tunable rotator.Ingeniería, Industria y Construcció

Diseño de medios EBG basados en estructuras quirales

In this work, a new EBG structure with inclusions of chiral elements is presented. We have studied the effect of crank type chiral inclusions on the propagation along a microstrip line and compared with the effects produced by mushroom type inclusions. It has been found that the inclusion of a row of structures of high chirality on both sides of a transmission line produces a band gap of wider bandwidth, to that obtained by the inclusion of other known elements used to create EBG media such as mushroom type structures. The current structure works in X-Band (8.2-12.4 GHz) but is easily applicable to other frequencies changing the size of crank inclusions.Ingeniería, Industria y Construcció

Green's formulation for chirowaveguides

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)

Variación de la temperatura en las capas externas del cuerpo humano irradiado a alta frecuencia (HF)

The absorption of energy by human external tissue when HF irradiation and the physical consequences involved are the purposes of this study. When it is directed toward the surface of the skin, energy is transmitted to its inner layers causing an increase of the temperature. This process has experimentally been proved to be beneficial in many cases. Yet theoretically there is still a slightly hollow basis about it. Skin tissue is actually a multilayer tissue with a different characteristic in each layer. Each one of them is characterized by some parameters, such as permittivity, conductivity, density and specific heat. Two kinds of skin tissues will be analyzed: a fibrous and a fatty one, each of both with a different skin humidity. Our model takes into account the heating by HF radiation, the redistribution of energy through the tissues and the cooling rate by blood in order to predict the increasing of tissue temperature in differents situations.Ingeniería, Industria y Construcció

Caracterización Electromagnética de Medios Quirales

Experimental techniques for chiral media characterization at microwave frequencies are reviewed. Free-wave, waveguide and resonators techniques found in the current literature and the author’s own experience are discussed. Some free-wave results are presented. Finally, a critical discussion about each technique feasibility is presented.Ingeniería, Industria y Construcció

Transferencia de calor mediante la aplicación de RF sobre un modelo multicapa de tejido dérmico

HF radiation applied on the surface of the skin by an electrode is absorbed and it causes interior changes that redound into a smoother skin with less wrinkles. In this study, it is exposed a multiplayer method to determine absorbed radiation and increasing of temperature for each internal tissue. Each tissue is represented by a layer with certain parameters, such as permittivity, conductivity, density and specific heat. The model is applied to two different distributions of tissues: a fibrous and a fatty one. It is found that a fibrous distribution absorbs more energy than a fatty one, and also how the absorption could even be increased by previous humidification.Ingeniería, Industria y Construcció