Antenas de microfita com patch em anel e múltiplas camadas dielétricas anisotrópicas uniaxiais

This work presents an analysis of the annular ring microstrip antennas printed on uniaxial anisotropic substrates and with superstrate.The analysis uses the full-wave formulation by means of the Hertz vector potentials method, in the Hankel transform domain. The definition of the Hertz vector potentials and the application of the appropriate boundary conditions to the structure allow determining the dyadic Green functions, relating the current densities in the conducting patch to the transforms of the tangential electric field components. Galerkin s method is then used to obtain the matrix equation whose nontrivial solution gives the complex resonant frequency of the antenna. From the modeling, it is possible to obtain results for the resonant frequency, bandwidth and quality factor, as a function of several parameters of the antenna, for different configurations. We have considered annular ring microstrip antennas on a single dielectric layer, antennas with two anisotropic dielectric layers, and annular ring microstrip antennas on suspended substrates. Numerical results for the resonant frequency of the these structures printed on isotropic substrates are also presented and compared with those published by other authors, showing a good agreement

Desenvolvimento de antenas de microfita com aberturas nos patches condutores através do método da segmentação

Microstrip antennas are widely used in modern telecommunication systems. This is particularly due to the great variety of geometries and because they are easily built and integrated to other high frequency devices and circuits. This work presents a study of the properties of the microstrip antenna with an aperture impressed in the conducting patch. Besides, the analysis is performed for isotropic and anisotropic dielectric substrates. The Multiport Network Model MNM is used in combination with the Segmentation Method and the Greens function technique in the analysis of the considered microstrip antenna geometries. The numerical analysis is performed by using the boundary value problem solution, by considering separately the impedance matrix of the structure segments. The analysis for the complete structure is implemented by choosing properly the number and location of the neighboor element ports. The numerial analysis is performed for the following antenna geometries: resonant cavity, microstrip rectangular patch antenna, and microstrip rectangular patch antenna with aperture. The analysis is firstly developed for microstrip antennas on isotropic substrates, and then extended to the case of microstrip antennas on anisotropic substrates by using a Mapping Method. The experimental work is described and related to the development of several prototypes of rectangular microstrip patch antennas wtih and without rectangular apertures. A good agreement was observed between the simulated and measured results. Thereafter, a good agreement was also observed between the results of this work and those shown in literature for microstrip antennas on isotropic substrates. Furthermore, results are proposed for rectangular microstrip patch antennas wtih rectangular apertures in the conducting patch

Análise do espalhamento espectral em superfícies de estruturas complexas para comunicações móveis

In this work, the transmission line method is explored on the study of the propagation phenomenon in nonhomogeneous walls with finite thickness. It is evaluated the efficiency and applicability of the method, considering materials like gypsum, wood and brick, found in the composition of the structures of walls in question. The results obtained in this work are compared to those available in the literature, for several particular cases. A good agreement is observed, showing that the performed analysis is accurate and efficient in modeling, for instance, the wave propagation through building walls and integrated circuit layers in mobile communication and radar system applications. Later, simulations of resistive sheets devices such as Salisbury screens and Jaumann absorbers and of transmission lines made of metal-insulator-semiconductor (MIS) are made. Thereafter, it is described a study on frequency surface selective structures (FSS). It is proposed the development of devices and microwave integrated circuits (MIC) of such structures, for the accomplishment of experiments. Finally, future works are suggested, for instance, on the development of reflectarrays, frequency selective surfaces with dissimilar elements, and coupled frequency selective surfaces with elements located on different layers

Análise de antenas de microfita com patches circulares sobre substratos anisotrópicos usando o método dos potenciais de Hertz

This work consists on the theoretical and numerical analysis of some properties of circular microstrip patch antennas on isotropic and uniaxial anisotropic substrates. For this purpose, a full wave analysis is performed, using Hertz Vector Potentials method in the Hankel Transform domain. In the numerical analysis, the moment method is also used in order to determine some characteristics of the antenna, such as: resonant frequency and radiation pattern. The definition of Hertz potentials in the Hankel domain is used in association with Maxwell´s equations and the boundary conditions of the structures to obtain the Green´s functions, relating the components of the current density on the patch and the tangential electric field components. Then, the Galerkin method is used to generate a matrix equation whose nontrivial solution is the complex resonant frequency of the structure. In the analysis, a microstrip antenna with only one isotropic dielectric layer is initially considered. For this structure, the effect of using superconductor patches is also analyzed. An analysis of a circular microstrip antenna on an uniaxial anisotropic dielectric layer is performed, using the Hertz vector potentials oriented along the optical axis of the material, that is perpendicular to the microstrip ground plane. Afterwards, the circular microstrip antenna using two uniaxial anisotropic dielectric layers is investigated, considering the particular case in which the inferior layer is filled by air. In this study, numerical results for resonant frequency and radiation pattern for circular microstrip antennas on isotropic and uniaxial anisotropic substrates are presented and compared with measured and calculated results found in the literature

Caracterização de circuitos planares de micro-ondas pelo método iterativo das ondas

The planar circuits are structures that increasingly attracting the attention of researchers, due the good performance and capacity to integrate with other devices, in the prototyping of systems for transmitting and receiving signals in the microwave range. In this context, the study and development of new techniques for analysis of these devices have significantly contributed in the design of structures with excellent performance and high reliability. In this work, the full-wave method based on the concept of electromagnetic waves and the principle of reflection and transmission of waves at an interface, Wave Concept Iterative Procedure (WCIP), or iterative method of waves is described as a tool with high precision study microwave planar circuits. The proposed method is applied to the characterization of planar filters, microstrip antennas and frequency selective surfaces. Prototype devices were built and the experimental results confirmed the proposed mathematical model. The results were also compared with simulated results by Ansoft HFSS, observing a good agreement between them.

Multiplicando veredas entre guimarães rosa e oswaldo lamartine

Universidade Federal do Rio Grande do Norte

Guimarães Rosa: travessia

This study develops a reading of five tales of Guimarães Rosa: “A hora e vez de Augusto Matraga”, “Campo Geral”, “A Benfazeja”, “Esses Lopes” and “Meu tio o Iauaretê”, included, respectively, in Sagarana, Corpo de Baile, Primeiras Estórias, Tutaméia and Estas Estórias. Then, undertakes a brief course in order to observe in the creative genesis of the author a manichean theme, whose view of the world, with poetic intensity, opposes the good and the evil. This research thus has drawn upon the Mythical Symbolism, in Literary Criticism and aspects of Metaphisics, in addition to analyzing classic literary essays in approaching of histories masterpiece structure. It has also demonstrate that in the rosiano hinterland the contradictory contributes to the speculation about the human man, in the continuous learning of his passing

Ser-tão de Buriti: o corpo de noturno rumor (a poética de Guimarães Rosa e o pensamento literário contemporâneo)

This thesis is to analyze the fictional texture of Buriti, novella by Guimarães Rosa, which makes part of Corpo do Baile. Gilles Deleuze‘s philosophical background as well as similar theorists such as Mircea Eliade, Derrida, Bataille, Foucault, Blanchot and Nie-tzsche constitute the main reference, as example of Guimarães Rosa‘s problematizing writing, since they present as basic element of thought the desterritorialization of con-cepts, standards and institutionalized knowledge by the dominant literary language. Along with the theoretical perspective of current alterity on these authors, Buriti is crossed by one aesthetics substantiated with a multiplicity of narrative points of view, opening gaps to other non-sacralized, nomadic voices, using polyphony as a way of breaking and destabilizing crystallized truths related to the canons of mother tongue. Interwoven by a poetic side of transgression, the narrative of Buriti finds especially marked by the signs of the backlands and of the night, which rhizomatically point to a sense of infinity, eternity, loneliness, vertigo before the abyssal, evoking the singularity of a ser-tão before the night, "the body of nocturnal rumor." The nights in the backlands in Buriti give rise to the emergence of a state of subjectivity, the ser-tão, whose nature is shown as a space of communion of the various beings that humans put on the same level of other living beings, setting up a sharing cosmic territory, enjoyment between pain and pleasure, between death and life. It is the night in the darkness, the shadows, the ser-tão is exposed, the being in his depth, facing himself with his internal rumors, which project themselves through the noise, the sound amplified by the vastness of the night at the desert backlands. "The backlands is the night." (ROSA, 1988, p.92).

Ser-tão de Buriti: o corpo de noturno rumor (a poética de Guimarães Rosa e o pensamento literário contemporâneo)

This thesis is to analyze the fictional texture of Buriti, novella by Guimarães Rosa, which makes part of Corpo do Baile. Gilles Deleuze‘s philosophical background as well as similar theorists such as Mircea Eliade, Derrida, Bataille, Foucault, Blanchot and Nie-tzsche constitute the main reference, as example of Guimarães Rosa‘s problematizing writing, since they present as basic element of thought the desterritorialization of con-cepts, standards and institutionalized knowledge by the dominant literary language. Along with the theoretical perspective of current alterity on these authors, Buriti is crossed by one aesthetics substantiated with a multiplicity of narrative points of view, opening gaps to other non-sacralized, nomadic voices, using polyphony as a way of breaking and destabilizing crystallized truths related to the canons of mother tongue. Interwoven by a poetic side of transgression, the narrative of Buriti finds especially marked by the signs of the backlands and of the night, which rhizomatically point to a sense of infinity, eternity, loneliness, vertigo before the abyssal, evoking the singularity of a ser-tão before the night, "the body of nocturnal rumor." The nights in the backlands in Buriti give rise to the emergence of a state of subjectivity, the ser-tão, whose nature is shown as a space of communion of the various beings that humans put on the same level of other living beings, setting up a sharing cosmic territory, enjoyment between pain and pleasure, between death and life. It is the night in the darkness, the shadows, the ser-tão is exposed, the being in his depth, facing himself with his internal rumors, which project themselves through the noise, the sound amplified by the vastness of the night at the desert backlands. "The backlands is the night." (ROSA, 1988, p.92).