Metamaterial inspired improved antennas and circuits

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Análise e síntese de antenas e superfícies seletivas de frequência utilizando computação evolucionária e inteligência de enxames

The frequency selective surfaces, or FSS (Frequency Selective Surfaces), are structures consisting of periodic arrays of conductive elements, called patches, which are usually very thin and they are printed on dielectric layers, or by openings perforated on very thin metallic surfaces, for applications in bands of microwave and millimeter waves. These structures are often used in aircraft, missiles, satellites, radomes, antennae reflector, high gain antennas and microwave ovens, for example. The use of these structures has as main objective filter frequency bands that can be broadcast or rejection, depending on the specificity of the required application. In turn, the modern communication systems such as GSM (Global System for Mobile Communications), RFID (Radio Frequency Identification), Bluetooth, Wi-Fi and WiMAX, whose services are highly demanded by society, have required the development of antennas having, as its main features, and low cost profile, and reduced dimensions and weight. In this context, the microstrip antenna is presented as an excellent choice for communications systems today, because (in addition to meeting the requirements mentioned intrinsically) planar structures are easy to manufacture and integration with other components in microwave circuits. Consequently, the analysis and synthesis of these devices mainly, due to the high possibility of shapes, size and frequency of its elements has been carried out by full-wave models, such as the finite element method, the method of moments and finite difference time domain. However, these methods require an accurate despite great computational effort. In this context, computational intelligence (CI) has been used successfully in the design and optimization of microwave planar structures, as an auxiliary tool and very appropriate, given the complexity of the geometry of the antennas and the FSS considered. The computational intelligence is inspired by natural phenomena such as learning, perception and decision, using techniques such as artificial neural networks, fuzzy logic, fractal geometry and evolutionary computation. This work makes a study of application of computational intelligence using meta-heuristics such as genetic algorithms and swarm intelligence optimization of antennas and frequency selective surfaces. Genetic algorithms are computational search methods based on the theory of natural selection proposed by Darwin and genetics used to solve complex problems, eg, problems where the search space grows with the size of the problem. The particle swarm optimization characteristics including the use of intelligence collectively being applied to optimization problems in many areas of research. The main objective of this work is the use of computational intelligence, the analysis and synthesis of antennas and FSS. We considered the structures of a microstrip planar monopole, ring type, and a cross-dipole FSS. We developed algorithms and optimization results obtained for optimized geometries of antennas and FSS considered. To validate results were designed, constructed and measured several prototypes. The measured results showed excellent agreement with the simulated. Moreover, the results obtained in this study were compared to those simulated using a commercial software has been also observed an excellent agreement. Specifically, the efficiency of techniques used were CI evidenced by simulated and measured, aiming at optimizing the bandwidth of an antenna for wideband operation or UWB (Ultra Wideband), using a genetic algorithm and optimizing the bandwidth, by specifying the length of the air gap between two frequency selective surfaces, using an optimization algorithm particle swarm

Modelagem em SystemC-AMS de uma plataforma compatível com o sistema de coleta de dados brasileiro

This work presents simulation results of an identification platform compatible with the INPE Brazilian Data Collection System, modeled with SystemC-AMS. SystemC-AMS that is a library of C++ classes dedicated to the simulation of heterogeneous systems, offering a powerful resource to describe models in digital, analog and RF domains, as well as mechanical and optic. The designed model was divided in four parts. The first block takes into account the satellite s orbit, necessary to correctly model the propagation channel, including Doppler effect, attenuation and thermal noise. The identification block detects the satellite presence. It is composed by low noise amplifier, band pass filter, power detector and logic comparator. The controller block is responsible for enabling the RF transmitter when the presence of the satellite is detected. The controller was modeled as a Petri net, due to the asynchronous nature of the system. The fourth block is the RF transmitter unit, which performs the modulation of the information in BPSK ±60o. This block is composed by oscillator, mixer, adder and amplifier. The whole system was simulated simultaneously. The results are being used to specify system components and to elaborate testbenchs for design verification

Deciding difference logic in a Nelson-Oppen combination framework

O método de combinação de Nelson-Oppen permite que vários procedimentos de decisão, cada um projetado para uma teoria específica, possam ser combinados para inferir sobre teorias mais abrangentes, através do princípio de propagação de igualdades. Provadores de teorema baseados neste modelo são beneficiados por sua característica modular e podem evoluir mais facilmente, incrementalmente. Difference logic é uma subteoria da aritmética linear. Ela é formada por constraints do tipo x − y ≤ c, onde x e y são variáveis e c é uma constante. Difference logic é muito comum em vários problemas, como circuitos digitais, agendamento, sistemas temporais, etc. e se apresenta predominante em vários outros casos. Difference logic ainda se caracteriza por ser modelada usando teoria dos grafos. Isto permite que vários algoritmos eficientes e conhecidos da teoria de grafos possam ser utilizados. Um procedimento de decisão para difference logic é capaz de induzir sobre milhares de constraints. Um procedimento de decisão para a teoria de difference logic tem como objetivo principal informar se um conjunto de constraints de difference logic é satisfatível (as variáveis podem assumir valores que tornam o conjunto consistente) ou não. Além disso, para funcionar em um modelo de combinação baseado em Nelson-Oppen, o procedimento de decisão precisa ter outras funcionalidades, como geração de igualdade de variáveis, prova de inconsistência, premissas, etc. Este trabalho apresenta um procedimento de decisão para a teoria de difference logic dentro de uma arquitetura baseada no método de combinação de Nelson-Oppen. O trabalho foi realizado integrando-se ao provador haRVey, de onde foi possível observar o seu funcionamento. Detalhes de implementação e testes experimentais são relatados

Setor terciário e informalidade: algumas especificidades da (re)produção do espaço urbano de Bayeux-PB

This work has as study object the tertiary sector and (the re)production of the urban space of Bayeux-PB. For in such a way, one became necessary to the construction of a theoretical boarding that context the national reality, to be able itself to understand the reality local. This way to construct allowed an opening of the field of vision how much to the relevance of if ahead studying the tertiary sector and its weight of the current configuration of the society in a country as Brazil, e especially in a city of a State northeastern, as it is the case of Bayeux. The theoretical boarding had as base the two circuits of the urban economy, the productive reorganization and the transformations in the world of the work, as well as, the space organization and the distinction between the economic and social space of the tertiary activities, from the logic of functioning of the establishments: the regulation. Besides working with referring official data to the tertiary sector, the empirical study it had as reference one hundred and sixty and establishments tertiary, located in four axles of circulation of the city of Bayeux - PB, which are: Av. Liberdade, Av. Engenheiro de Carvalho, Av. Francisco Marques da Fonseca and Av. Marechal Rondon, that they had appeared in such a way stimulated for the processes of urbanization and industrialization lived deeply from years 70 in the "Great João Pessoa" how much, in the countries of the underdeveloped capitalist world, as Brazil. Being thus, the objective of the work was to study the tertiary sector and its relation with (the re)production of the urban space, standing out the functioning logic

O Circuito espacial de produção do biodiesel: configuração no território brasileiro e uso do território Norte-Rio-Grandense

This research aims to understand the use of the territory from the Rio Grande do Norte to the circuit spatial of production from the Biodiesel understanding it as part of the national context. The introduction of biodiesel into the Brazilian energy matrix begins to take shape in the year 2005 with the implementation of the National Program for Production and Use of Biodiesel (NPPB). This is anchored on three pillars: social inclusion (through family agriculture), environmental sustainability and economic viability. The NPPB consists of a set of standards, which turned into shares and distributed by almost all the national territory. Our reflection assumes that the places accommodating different forms of productive activities and, thus, the performance of the circuit space of biodiesel production depends on several factors, including the configuration of the territory they receive this new nexus economic. Understanding that the places by their technical content determine the realization of productive activities, it was found that the inclusion of this circuit space production in Rio Grande do Norte, reveals the reality expressed in the national territory, where some places are endowed with a privileged technical content and other extremely poor infrastructure. As our research could confirm the circuit space of biodiesel production that is expressed in the way plants are distributed within the country (mostly in South-Central), in more significant participation of small farmers in the South in the supply of raw material for the production of biodiesel and the main raw material used for the production of agrofuels (soybeans, whose production sector is highly consolidated and technified). Already the project materialization of NPPB regarding the settlements and communities of the Rio Grande do Norte State, we observed that the "event" or advent of realization encountered a technical means lacking in infrastructure that need to be molded to the needs of production, or is to cultivate castor beans or sunflower would be needed inputs and implements that farmers don´t have. Given the above, the research concludes that, as proposed previously, the use of the territory of Rio Grande do Norte to this circuit has summarized the performance of experiments, either with regard to the participation of family farmers as suppliers of raw materials, including the development of related research in the stage of production fuel oil by Petrobras. This finding came from research done from the concept of "spatial circuits of production," which allowed the verification of the circuit that steps outlined in Potiguar territory. Regarding the inclusion of family farmers in the productive circuit in RN, research reveals that, in the manner as has been done, it is doomed to failure. Furthermore, we dare say that this persistence in trying to put these family farmers, the way is being made, and the resulting successive failures, indicating that social inclusion advocated by NPPB not take place, and that this production circuit relies on the same logic circuit concentrated and exclusive space for ethanol production