FREIRE ROSALES , Manuel José

Este trabajo aborda el estudio del espectro modal del campo electromagnético excitado por fuentes de carácter práctico en líneas de transmisión de microondas tipo microtira. Para llevar a cabo este estudio se analiza la corriente excitada por una fuente de voltaje tipo delta-gap en líneas de longitud infinita. El carácter infinito de la línea...

his work investigates the use of a metasurface made up of a two-dimensional array of capacitively loaded metallic rings to enhance the signal-to-noise ratio of magnetic resonance imaging surface coils and to tailor the magnetic near-field radio frequency pattern of the coils. It is found that the signal-to-noise ratio is increased if the...

In this contribution, the basic concepts underlying the physics of magnetoinductive MI lenses are developed and the main practical limitations to their performances are analyzed. Strategies to overcome such limitations are proposed. Possible applications of MI lenses in magnetic resonance imaging are discussed.

Dispositivo para mejorar la sensibilidad de las bobinas receptoras en imágenes médicas por resonancia magnética.La presente invención tiene por objeto un dispositivo para mejorar la sensibilidad de las bobinas de superficie que se usan en la obtención de

A planar near-field magnetoinductive lens operating in the microwave range is presented. Theproposed device consists of two parallel planar arrays of metallic broadside coupledsBCdsplit-ringresonatorssSRRsd, or BC-SRRs. The power coming from a point-like source located in front of thelens is focused into a receiver located in free...

In this work, the previously reported near-field imaging by two strongly coupled arrays of planar magnetic resonators is further studied. Experiments are performed to clarify the physical mechanisms underlying such an effect. The specific aim of these experiments is to clarify both the role played by magnetoinductive surface waves MISWs and...

The usefulness of thin split ring metamaterial slabs for imaging applications, including magnetic resonance imaging applications, has attracted some attention in the past years. However, the small number of unit cells across these thin slabs prevents the direct application of continuous medium models for its characterization. The main aim of...

In this work, it is demonstrated that metamaterial lenses can help to increase the signal-to-noise ratio of magnetic resonance imaging coils in low-field magnetic resonance imaging systems. In low-field magnetic resonance imaging systems, the dominant source of noise in the signal-to-noise ratio comes from the metallization of the coil and the...

In this paper, a transmission-line model is developed for the computation of the insertion loss of magnetostatic-surface wave transducers and measurements are carried out by the authors to check this model. In a first step of the analysis, closed-form expressions for the solution of the telegrapher's equations for the two microstrip transducers...

This paper presents a new method for the complete characterization of the radiation of magnetostatic-surface waves in microstrip transmission lines with longitudinal magnetization. This method is based on the analysis of the excitation of leaky modes in microstrip lines and provides both the propagation constant and the complex impedance of the...

Transcranial static magnetic stimulation is a novel noninvasive method of reduction of the cortical excitability in certain neurological diseases that makes use of static magnetic fields generated by permanent magnets. By contrast, ordinary transcranial magnetic stimulation makes use of pulsed magnetic fields generated by strong currents....

We study the peculiarities of a metamaterial "superlens," caused by its discrete structure and finite size. We show that precise modeling of the lens provides remarkable distinctions from continuous medium approximation. In particular, we address the problem of highest resolution that can be achieved with a realistic electrically thin...

La invención consiste en un dispositivo para demostrar experimentalmente el fenómeno de la refracción negativa de microondas. El dispositivo comprende dos prismas, uno con índice de refracción positivo (6) y otro con índice negativo (5) a la frecuencia de

In this paper, we present a method for the evaluation of the signalto- 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...

This paper presents a theoretical and experimental study on the viability of obtaining two- and three-dimensional superresolution (i.e., resolution overcoming the diffraction limit for all directions in space) by means of metamaterial slab lenses. Although the source field cannot be actually reproduced at the back side of the lens with...

In this paper, we propose and study several new designs of a shunt capacitor filter with two surface-mount technology capacitors. These designs make use of mutual inductance effects to increase the attenuation provided by the filter in the range of high frequencies where the filter behaves inductively. We provide lumped element circuitmodels...

The method of moments in the spectral domain is applied to the full-wave analysis of aperture coupled microstrip antennas in the case where the substrate of the antennas is a layered medium containing magnetized ferrites. The subsectional basis functions used in the analysis make it possible to handle patch antennas and coupling apertures with...

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An experimental setup to demonstrate negative refraction is described. A simple method for designing and fabricating a metamaterial with negative refractive index at microwave frequencies is discussed. The metamaterial is made of a multilayer planar arrangement of flat unit cells. A prism was fabricated and used to demonstrate negative...

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...

Transduction of raagnetoinductive waves (MIWs) in planar technology is demonstrated. A transducer consisting of a one-dimensional periodic array of metallic split squared ring resonators (SSRR), placed between a pair of microstrip lines on a planar substrate has been fabricated and measured. The microstrip lines are inductively coupled to the...

Magnetic coupling between components in compact electromagnetic interference filters is one of the main effects that undermine their ability to reduce conducted emissions of power converters at frequencies above several hundreds of kilohertzs or a few megahertzs. This work analyzes and compares the performance of two different shielding...

We present experimental and numerical investigations of water flow in a microsystem induced by microwave electric fields. Microwave dielectric heating induces gradients of temperature which produce spatial variations in mass density and dielectric permittivity that lead to buoyancy and dielectric forces in the liquid, respectively. The...