Dispositivos planares integrados utilizando método dinâmico com metamateriais e PBG

This work presents a theoretical, numerical and computation analysis of parameters of a rectangular microstrip antenna with metamaterial substrate, fin line as a coupler and also integrated devices like integrated filter antenna. It is applied theory to full-wave of Transverse Transmission Line - TTL method, to characterize the magnitude of the substrate and obtain the general equations of the electromagnetic fields. About the metamaterial, they are characterized by permittivity and permeability tensor, reaching to the general equations for the electromagnetic fields of the antenna. It is presented a study about main representation of PBG(Photonic Band Gap) material and its applied for a specific configuration. A few parameters are simulated some structures in order to reduce the physical dimensions and increase the bandwidth. The results are presented through graphs. The theoretical and computational analysis of this work have shown accurate and relatively concise. Conclusions are drawn and suggestions for future work

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

Aplicações de Dispositivos de Microondas utilizando Substrato EBG/PBG para Comunicações Móveis

The modern society depends on an efficient communications system able to of transmitting and receiving information with a higher speed and reliability every time. The need for ever more efficient devices raises optimization techniques of microstrip devices, such as techniques to increase bandwidth: thicker substrates and substrate structures with EBG (Electromagnetic Band Gap) and PBG (Photonic Band Gap). This work has how aims the study of the application of PBG materials on substrates of planar structures in microstrip, more precisely in directional quadrature couplers and in rat-race and impedance of transformers. A study of the planar structures in microstrip and substrates EBG is presented. The PBG substrates can be used to optimize the radiation through the air, thus reducing the occurrence of surface waves and the resulting diffraction edge responsible for degradation of radiation pattern. Through specific programs in FORTRAN Power Station obtained the frequencies and couplings for each structure. Are used the program PACMO - Computer Aided Design in Microwave. Results are obtained of the frequency and coupling devices, ranging the frequency band used (cellular communication and Wimax systems) and the permittivity of the substrate, comparing the results of conventional material and PBG materials in the s and p polarizations.

Estudo do efeito de substratos metamateriais em parâmetros de antenas de microfita

Microstrip antennas are subject matter in several research fields due to its numerous advantages. The discovery, at 1999, of a new class of materials called metamaterials - usually composed of metallic elements immersed in a dielectric medium, have attracted the attention of the scientific community, due to its electromagnetic properties, especially the ability to use in planar structures, such as microstrip, without interfering with their traditional geometry. The aim of this paper is to analyze the effects of one and bidimensional metamaterial substrates in microstrip antennas, with different configurations of resonance rings, SRR, in the dielectric layer. Fractal geometry is applied to these rings, in seeking to verify a multiband behavior and to reduce the resonance frequency of the antennas. The results are then given by commercial software Ansoft HFSS, used for precise analysis of the electromagnetic behavior of antennas by Finite Element Method (FEM). To reach it, this essay will first perform a literature study on fractal geometry and its generative process. This paper also presents an analysis of microstrip antennas, with emphasis on addressing different types of substrates as part of its electric and magnetic anisotropic behavior. It s performed too an approach on metamaterials and their unique properties

Antenas monopolo planar com patch em anel circular para sistemas UWB

The microstrip antennas are largely used in wireless communication systems due to their low cost, weight, less complex construction and manufacturing, in addition to its versatility. UWB systems have emerged as an alternative to wireless communications over short distances because they offer of higher capacity and lower multipath distortion than other systems with the same purpose. Combining the advantages of microstrip antennas to the characteristics of UWB, it is possible to develop more and more smaller devices, with diverse geometries to operate satisfactorily in these systems. This paper aims to propose alternatives to microstrip antennas for UWB systems operate in the range between 3.1 and 10.6 GHz, with a patch on circular ring. Some techniques are analyzed and employed to increase the bandwidth of proposed antenna: the insertion of a parasitic elements and a rectangular slit in the displaced ground plane. For this, key issues are presented as the basic principles of UWB systems, the fundamental theory of antennas and microstrip antennas. The simulations and experimental characterization of constructed antennas are presented, as well as analysis of parameters such as bandwidth and radiation pattern

Análise cefalométrica: ortodontistas x radiologistas

Cephalometric analysis is the mensuration of linear and angular measures through demarcation points as distances and lines on teleradiography, and is considered of fundamental importance for diagnosis and orthodontic planning. In this manner, the objective of this research was to compare cephalometric measurements obtained by dentists and radiologists from the analysis of the same radiograph, in a computerized cephalometric analysis program. All research participants marked 18 cephalometric points on a 14-inch notebook computer, as directed by the program itself (Radiocef 2®). From there, they generated 14 cephalometric parameters including skeletal, dental-skeletal, dental and soft tissue. In order to verify the intra-examiner agreement, 10 professionals from each group repeated the marking of the points with a minimum interval of eight days between the two markings. The intra-group variability was calculated based on the coefficients of variation (CV). The comparison between groups was performed using the Student t-test for normally distributed variables, and using the Mann-Whitney test for those with non-normal distribution. In the group of orthodontists, the measurements of Pog and 1-NB, SL, S-Ls Line, S-Li Line and 1.NB showed high internal variability. In the group of radiologists, the same occurred with the values of Pog and 1-NB, S-Ls Line, S-Li Line and 1.NA. In the comparison between groups, all the analyzed linear values and two angular values showed statistically significant differences between radiologists and dentists (p <0.05). According to the results, the interexaminer error in cephalometric analysis requires more attention, but does not come from a specific class of specialists, being either dentists or radiologists.

Otimização do controle do diagrama de radiação de radares de varredura para rastreio de foguetes usando o método GAMMC para o Caso Planar (GAMMC-P)

Launching centers are designed for scientific and commercial activities with aerospace vehicles. Rockets Tracking Systems (RTS) are part of the infrastructure of these centers and they are responsible for collecting and processing the data trajectory of vehicles. Generally, Parabolic Reflector Radars (PRRs) are used in RTS. However, it is possible to use radars with antenna arrays, or Phased Arrays (PAs), so called Phased Arrays Radars (PARs). Thus, the excitation signal of each radiating element of the array can be adjusted to perform electronic control of the radiation pattern in order to improve functionality and maintenance of the system. Therefore, in the implementation and reuse projects of PARs, modeling is subject to various combinations of excitation signals, producing a complex optimization problem due to the large number of available solutions. In this case, it is possible to use offline optimization methods, such as Genetic Algorithms (GAs), to calculate the problem solutions, which are stored for online applications. Hence, the Genetic Algorithm with Maximum-Minimum Crossover (GAMMC) optimization method was used to develop the GAMMC-P algorithm that optimizes the modeling step of radiation pattern control from planar PAs. Compared with a conventional crossover GA, the GAMMC has a different approach from the conventional one, because it performs the crossover of the fittest individuals with the least fit individuals in order to enhance the genetic diversity. Thus, the GAMMC prevents premature convergence, increases population fitness and reduces the processing time. Therefore, the GAMMC-P uses a reconfigurable algorithm with multiple objectives, different coding and genetic operator MMC. The test results show that GAMMC-P reached the proposed requirements for different operating conditions of a planar RAV.