Programa de Pós-Graduação em Engenharia Elétrica e de Computação
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Doctoral Thesis Miniaturização de antenas de microfita para aplicações em CubeSats(Universidade Federal do Rio Grande do Norte, 2021-12-15) Silva, Wellington Guilherme da; Campos, Antônio Luiz Pereira de Siqueira; http://lattes.cnpq.br/1982228057731254; http://lattes.cnpq.br/6983229617567409; Gomes Neto, Alfredo; http://lattes.cnpq.br/1403715441701958; Andrade, Humberto Dionísio de; http://lattes.cnpq.br/1253785596446469; Mendonça, Laercio Martins de; http://lattes.cnpq.br/1853488415531363; Rodrigues, Márcio Eduardo da Costa; http://lattes.cnpq.br/2116993138825543The objective of this work was to develop a compact microstrip antenna for use in CubeSats, a type of miniaturized satellite used mainly by universities for space exploration and research, typically in low earth orbit. The small size of these satellites presents a great challenge to the project. Being one of the main components on board satellites, the antenna determines the performance of all wireless systems, including: telemetry, tracking and control (TT&C); downlink of high speed data; navigation; communications between satellites; radars; and sensors. For the TT&C function, expandable wire antennas are often employed in V-UHF. However, the release mechanism of these antennas can fail and compromise the mission. A microstrip antenna has several advantages such as reduced size, low weight and absence of mechanical parts. Therefore, a compact microstrip antenna is desirable in this type of application. The work presents a bibliographical review covering some concepts about the CubeSat pattern, the fundamentals of antenna theory, the main techniques of miniaturization of antennas, the fundamentals of electrically small antennas and the main works already developed on the subject. An additional investigation was carried out on Wheeler’s method for measuring the radiation efficiency of compact antennas, this method being applied to measure the radiation efficiency of the built prototype. The work methodology consisted of designing, simulating, building and characterizing a microstrip antenna operating at two frequencies (401.6 MHz and 435.0 MHz) based on the fundamentals of the literature review. These frequencies were chosen to meet the requirements of most CubeSats in use, but in particular they serve two of the frequencies planned for CONASAT, a project by the Northeast Regional Center (CRN) of the National Institute for Space Research (INPE), located in Natal, in partnership with the Federal University of Rio Grande do Norte (UFRN). To confirm the applicability of the developed prototype, a complete characterization of the link was carried out considering all the gains and losses involved. The contribution of this work lies in the ability of the developed prototype to operate at two frequencies with a single power point, thus reducing the weight, complexity and risk of failures in the CubeSats communication systems.Doctoral Thesis Aprimoramento de largura de banda de antena de microfita usando metasuperfície para aplicações em Wi-Fi 5 e 6(Universidade Federal do Rio Grande do Norte, 2021-02-18) Araújo, Felipe Ferreira de; Campos, Antônio Luiz Pereira de Siqueira; D'Assunção, Adaildo Gomes; ; http://lattes.cnpq.br/4159638862269940; ; http://lattes.cnpq.br/1982228057731254; ; http://lattes.cnpq.br/6573890509544616; Silva Neto, Valdemir Praxedes da; ; http://lattes.cnpq.br/4160231554601828; Gomes Neto, Alfredo; ; http://lattes.cnpq.br/1403715441701958; Silva, Jefferson Costa e; ; http://lattes.cnpq.br/7399512856151138The microstrip antennas are the object of study in several research fields due to their advantages such as: small thickness, reduced weight and easy integration of electronic circuits. Similarly, the evolution observed in the development of microstrip antennas has also been noted in relation to the metasurfaces, a two-dimensional version of a metamaterial. Metasurfaces are artificial materials that are not found in nature and have unconventional electromagnetic characteristics, such as the index of refraction and coefficients of electrical permittivity and negative magnetic permeability, in addition, they have the ability to be used in planar structures, such as microstrip, without interfering with its traditional geometry. The objective of this work is to increase the bandwidth of a microstrip antenna using a new metasurface model. This new geometry is used to generate high order modes in the antenna and with rotation of the metasurface in relation to the antenna we can overlap the modes and obtain a large bandwidth. The proposed antenna presents bandwidth from 5.1 GHz to 8.0 GHz and can be applied in WiFi 5 and 6. Numerical results were chosen with the Ansys HFSS software. A prototype was built and built for S11 and gains were made. The numerical and experimental results are in agreement.Doctoral Thesis Aplicação de Células Metamateriais CLL ao projeto de antenas de microfita retangulares(Universidade Federal do Rio Grande do Norte, 2020-10-23) Lima, Adelson Menezes; Silva, José Patrocínio da; ; http://lattes.cnpq.br/5753289728835624; ; http://lattes.cnpq.br/5027012430953926; Campos, Antônio Luiz Pereira de Siqueira; ; http://lattes.cnpq.br/1982228057731254; Sena, Francisco das Chagas Barbosa de; ; http://lattes.cnpq.br/0166555495027599; Andrade, Humberto Dionísio de; ; http://lattes.cnpq.br/1253785596446469; Sousa Júnior, Vicente Ângelo de; ; http://lattes.cnpq.br/6358312955522220Obtaining and integrating solutions for technologies in the area of telecommunications has led researchers to investigate various materials, such as metamaterials in the construction of microwave circuits. Due to the ease of construction, microstrip antennas have used these materials that are not found in nature, as they have the possibility to manipulate their electromagnetic properties, making them interesting for the performance of antennas and various applications. In this context, the present work presents metamaterial cells and configurations in the form of periodic arrangements, immersed in the dielectric material, for the construction of the microstrip antennas. The analyzed antennas were designed for the operating frequency of 5.8 GHz. Simulations with the HFSS® software that uses the Finite Element method, were performed to analyze the electromagnetic characteristics of the cell and the parameters of the antennas, and thus investigating the influence of the arrangements in two case studies. Numerical results showed that the cell under study has a strong influence on the magnetic permeability in the metamaterial cell at the desired frequency. In the first case, there was a greater bandwidth and better impedance matching. In the second case, despite obtaining greater bandwidth, there was a decrease in the resonance frequency and a change in the impedance matching when the cells were rotated. To validate the results, prototypes were built for the first case under analysis and the measured results were compared to those obtained numerically, in which both showed good agreement. In the second study, only simulated results were obtained, considering the angle of rotation of the cells, ranging from 0 to 90 degrees with intervals of 15 degrees. For all the studied structures, the parameters the parameters analyzed were the reflection coefficient in dB (S11), bandwidth, polar and rectangular Smith chart, radiation diagram (2D and 3D), gain, Cross Polarization and Co-Polarization, as well such as the distribution of the electric field and the density of surface current.Master Thesis Análise de antenas planares para aplicações médicas nas bandas ISM de 435 MHz, 915 MHz e 2,45 GHz(Universidade Federal do Rio Grande do Norte, 2020-01-10) Nogueira, Jurgen Klinsmann Azevedo; D'Assunção, Adaildo Gomes; Silva Neto, Valdemir Praxedes da; ; ; ; http://lattes.cnpq.br/3159722016018256; Mendonça, Laercio Martins de; ; Lins, Hertz Wilton de Castro; ; Oliveira, João Bosco Lucena de; ; Oliveira, José de Ribamar Silva;Wireless devices are presented, in the most recent researches, as alternatives for monitoring various medical parameters, with applications in the frequency bands designated for Medical Device Radiocommunications Service - MedRadio (401 - 405 MHz), Medical Implant Communication Services - MICS (402 - 405 MHz) and Industrial, Scientific and Medical - ISM (433 - 435.8 MHz; 902 - 928 MHz; 2.4 - 2.5 GHz), with the possibility of performing invasive and non-invasive analyzes on human tissue or equivalent samples, replacing human tissue. In this dissertation, a parametric analysis of three rectangular antennas is performed, with slits positioned close to the edges of the patch, for sensing. Frequency responses of planar microstrip antennas with medical applications in the ISM band are presented in the three frequency bands (433 - 435.8 MHz; 902 - 928 MHz; 2.4 - 2.5 GHz). The results of the simulations were obtained by the Ansoft HFSS software for resonance frequency, bandwidth, reflection coefficient, specific absorption rate and sensitivity. The measurements were performed with solid samples of pork. A mathematical model was created to characterize the relative permittivity of the samples. The simulated and measured results showed excellent agreement and confirm the possibility of use in medical applications for monitoring and transmitting information, in addition to measurements of meat properties, replacing human tissue.Doctoral Thesis Síntese de uma nova tinta condutiva para circuitos de micro-ondas impressos sobre substrato de vidro e fibra de vidro(2019-05-31) Mesquita, Marcelo David Silva de; D'Assunção, Adaildo Gomes; ; ; D'Assunção Júnior, Adaildo Gomes; ; Silva, Jefferson Costa e; ; Oliveira, João Bosco Lucena de; ; Mendonça, Laercio Martins de; ; Giraldi, Maria Thereza Miranda Rocco;This thesis describes the work carried out for the synthesis of new conductive ink, with a high concentration of silver particles, and its use is proposed as an alternative to the use of conventional techniques of manufacturing microwave integrated circuits. The importance of the use of conductive ink is associated with the ease, efficiency, versatility, and reduction of manufacturing costs of the integrated circuits, by using small brushes for the application on various dielectric materials. Research on the use of conductive ink has carried out in the development of microstrip antennas, bioinspired frequency selective surfaces (FSS), direct current blockers (DC blockers) and directional couplers. The simulation and the design of these circuits were performed with the software Ansys Designer and Ansys HFSS. The investigation of the behavior of frequency scattering parameters these circuits, which allowed the evaluation of aspects related to transmission, reflection, coupling, radiation and electromagnetic wave filtering. In order to validate the results of the simulations and to compare the experimental results, prototypes of these circuits with copper laminates and with surfaces painted were fabricated and measured. The good agreement observed between the simulated and measured results for the prototypes of microwave integrated circuits painted with silver ink confirms the efficiency and versatility of the printing procedure with the use of the synthesized conductive ink.Doctoral Thesis Análise da determinação da constante elétrica de materiais sólidos e líquidos usando parâmetros de transmissão na faixa de microondas(2018-09-28) Soffiatti, André; Mendonça, Laercio Martins de; Mendonça, Laercio Martins de; ; ; ; D'Assunção, Adaildo Gomes; ; Silva, Cláudio Rodrigues Muniz da; ; Martins, Joemia Leilane Gomes de Medeiros; ; Melo, Marcos Tavares de;With the rapid growth of technology, it has become necessary to develop sensory devices for the control and automation of various agricultural, pharmaceutical and food processes in order to better understand the dielectric properties of materials and measurement techniques. This work presents an investigation and construction of an electromagnetic sensor system based on planar and non-planar antennas that are used to evaluate impurities in solid and liquid substances according to the quality of transmission between them. For this, a dedicated configuration was implemented with tests in several frequencies, to monitor the behavior of the transmission variation between the antennas using the free space method. Transmission analysis was also performed between the sensors, varying the angles of transmitted signal incidence and distance. The proposed sensor system was tested at several frequencies resulting in different sensitivity values. The prototypes were constructed and tested to analyze the dielectric effects of impurities in liquid substances of Epocler, NaCl and C2H4O2 and solid in medicaments such as tablets and capsules of different sizes and weights. The methodology used a simple technique to calculate the parameters of scattering [S] in solids and liquids and with its processing to obtain the dielectric properties of the materials considered. In addition, a mathematical model is presented for the transmission parameters related to the dielectric constant εr. In the experimental procedures, the parameters [S] are collected in free space by the Vector Network Analyzer (VNA), using horn antennas and also planar antennas with metamaterial. The theoretical and experimental results are validated through metric coherences obtained.Master Thesis Obtenção de parâmetros construtivos para antenas de microfita utilizando o Método Taguchi de otimização(2017-11-24) Lira, Ruann Víctor de Andrade; Campos, Antonio Luiz Pereira de Siqueira; ; ; Silva, Gutembergue Soares da; ; Silva, José Patrocinio da; ; Maniçoba, Robson Hebraico Cipriano;The applications of microstrip antennas cover a large area of Telecommunications, especially in systems that require components of volume and reduced weight, such as aerospace communications. Hence numerous researchers have been studying, more and more, techniques of optimization in the design of these antennas. Thus, this work has as main objective the optimization of microstrip antenna design. For this, the Taguchi Method is used in which each physical parameter is defined from the frequency of operation desired by the user, of the electric characteristics of the dielectric that will be used to make the antenna (substrate thickness and dielectric constant of the material) and definition of optimization limits (maximum and minimum values) that physical parameters can achieve. Specifically, the analysis uses the Taguchi method with boundary treatment so that the optimum final value does not fall outside the specified range. In the analysis, rectangular and circular patches are considered for projects in the frequency bands specific to WLAN. In the paper, numerical and experimental results are presented for loss of return. Comparisons are made between these results. A good agreement between the results is observed. Suggestions for continuity of work are also presented.Doctoral Thesis Inteligência computacional aplicada na otimização de efeitos causados pelo uso de estruturas PBG em antenas de microfita(2016-12-02) Guimarães, Ádller de Oliveira; Silva, José Patrocínio da; ; http://lattes.cnpq.br/5753289728835624; ; http://lattes.cnpq.br/8161855994548078; Fernandes, Humberto César Chaves; ; http://lattes.cnpq.br/0246709532151067; Pereira, Jonathan Paulo Pinheiro; ; http://lattes.cnpq.br/6437383890881181; Mendonça, Laercio Martins de; ; http://lattes.cnpq.br/1853488415531363; Sousa Neto, Marinaldo Pinheiro de; ; http://lattes.cnpq.br/2524160890713257The increasing demand for wireless technology in contemporary society requires the construction of integrated microwave circuits each time more sophisticated. In this sense, the planar microstrip antenna stands out because their small sizes and used in various applications, with emphasis on airplanes, satellites and mobile communication systems. In addition, recent researches shows the use of computing intelligence in telecommunications for analysis of new applications at microstrip antennas, as also the optimization of existing applications, searching for a better performance at the reception and / or signal transmission. In this context, this work has as objective get the radiation properties of microstrip antennas using the new models of Photonic Band Gap (PBG) structures based in meshes with periodic distributions and quasi-periodic printed on the substrate. In the practical procedures, prototypes of antennas were constructed that were used to obtain a database to feed the training process of an Artificial Neural Network (ANN), in order to obtain the resonance frequency of antennas. Finally, it was optimized the procedure for obtaining the project frequency and PBG structure required for a given operating frequency. According to the results, it can be concluded that it is possible to use an ANN in the optimization of a project of microstrip antenna with PBG substrate. The validation of the results provided by the ANN was based on building prototypes of the antennas, which showed good agreement between the simulated and measured values.Master Thesis Estudo da interferência de uma metasuperfície no desempenho das antenas de microfita(2016-12-16) Santos, Rafael Celestino dos; Campos, Antonio Luiz Pereira de Siqueira; ; http://lattes.cnpq.br/1982228057731254; ; http://lattes.cnpq.br/2406371613960468; Braz, Erico Cadineli; ; http://lattes.cnpq.br/9382571991103772; Martins, Ronaldo de Andrade; ; http://lattes.cnpq.br/0978273656336966This paper aims to present the influence of a metasurface, a special type of metamaterials, in the performace of microstrip antennas. The metasurface are artificial materials that are not found in a conventional manner in nature and do not have conventional electromagnetic characteristics such as refractive index and coefficient of permittivity and negative magnetic permeability which causes attractive electromagnetic effects for various applications, such as: improving the performance of a microstrip antenna as will be shown in this work. We started the work showing a brief history, definitions and electromagnetic properties of the antennas, microstrip antennas, metamaterials and metasuperfícies. Next, we will design and manufacture a microstrip antenna with and without the use of a metasurface where we will simulate through HFSS Ansoft Designer software and test in the laboratory with the E5071C ENA Network Analyzer. Finally, we will perform a comparative analysis, showing how the metasurface improves the performance of a microstrip antenna by analysis of the various parameters antenna, such as: return loss, power gain, directivity and input impedance.Master Thesis Desenvolvimento de antenas de microfita miniaturizadas com polarização circular para sistemas de comunicações sem fio(2016-06-27) Santos, Heric Weverton dos; D'Assunção, Adaildo Gomes; ; ; http://lattes.cnpq.br/5705066299844360; Mendonça, Laercio Martins de; ; http://lattes.cnpq.br/1853488415531363; D'Assunção Júnior, Adaildo Gomes; ; Oliveira, José de Ribamar Silva; ; http://lattes.cnpq.br/4002176927695547Recently, the growing demand for new technologies in telecommunications has generated much attention from the scientific community. The development of RF systems, the phenomenon of convergence services in a single device and the expansion of wireless communications networks have required the development of new antennas, with low cost, small size and increasingly specific properties. In this context, planar microstrip antennas have been widely used by the industry. In certain mobile communication systems such as radar, satellite, and Global Positioning System (GPS), the use of circularly polarized antennas has gained great emphasis, since, due to their electromagnetic characteristics, the circular polarization enables good performance even in environments subject to severe weather conditions and has small dependence on the misalignment of the transmitting and receiving antennas. This dissertation proposal is based on the analysis and development of single feed miniaturized circularly polarized microstrip antennas. Different techniques are investigated to provide microstrip antennas circular polarization and size miniaturization. In addition, based on theoretical and parametric analyses, new antennas configurations are proposed for applications in wireless communication systems. Several prototypes are built and measured for validation purpose. A good agreement is observed between simulation and measurements results.