Programa de Pós-Graduação em Engenharia Elétrica e de Computação
Permanent URI for this communityhttps://repositorio.ufrn.br/handle/123456789/11949
Browse
4 results
Search Results
Doctoral Thesis Novas configurações de sensores planares para a caracterização não-destrutiva de materiais magneto-dielétricos em micro-ondas(Universidade Federal do Rio Grande do Norte, 2025-01-30) Nogueira, Jurgen Klinsmann Azevedo; D'Assunção, Adaildo Gomes; Silva Neto, Valdemir Praxedes da; https://orcid.org/0000-0003-3867-3297; http://lattes.cnpq.br/4160231554601828; http://lattes.cnpq.br/4159638862269940; http://lattes.cnpq.br/3159722016018256; Costa, Cláudio Pereira da; https://orcid.org/0000-0003-2073-8291; http://lattes.cnpq.br/7571127714246653; Carvalho, Joabson Nogueira de; https://orcid.org/0000-0001-8173-1160; http://lattes.cnpq.br/3511078820928127; Oliveira, João Bosco Lucena de; https://orcid.org/0000-0002-8946-2521; http://lattes.cnpq.br/1360004695124740; Mendonça, Laércio Martins de; https://orcid.org/0000-0001-7861-3761; http://lattes.cnpq.br/1853488415531363This work presents the design and fabrication of two new configurations of planar microstrip devices for sensing applications and to characterize non-destructively the complex permittivity of magneto-dielectric materials. Planar microwave sensors have demonstrated important functionalities in several applications, such as in the food, industrial and biomedical sectors. Microwave sensors have the advantages of low cost and ease of fabrication, in addition to the possibility of integration with other devices. The first proposed sensor is based on a two-port planar microstrip device with the insertion of a Complementary Split Ring Resonator (CSRR) in its patch, this element is responsible for determining the electrical properties of the materials under test (MUT). Two samples of materials widely known in the literature were investigated. With the first proposed sensor, it was possible to obtain the complex permittivity of two solid materials. The second proposed sensor is based on a bioinspired microstrip planar antenna with a change in the ground plane structure (Defected Ground Structure – DGS), in order to obtain, also in a non-destructive way, the magneto-dielectric characteristics, i.e., the electrical permittivity and magnetic permeability, of nine solid materials also known in the literature, using the same resonator for both characterizations. The proposed sensor has a patch bioinspired by the Spondias Tuberosa leaf, and a CSRR was inserted in the center of the ground plane, responsible for the permittivity characterization. The permeability was obtained by means of slits positioned close to the CSRR. In this work, the sensitivities of the two proposed sensors were also analyzed, presenting excellent results. The sensors were analyzed by means of simulations in the commercial software Ansys HFSS. The prototypes were manufactured using the FR-4 dielectric, which has a relative electrical permittivity of 4.4, a loss constant of 0.02 and a thickness of 1.57 mm, and the measurements were performed using the E5071C vector network analyzer (VNA) on nine different samples (MUT) of dielectric and magnetic materials. The simulated and measured results were discussed and compared with values found in the literature, showing good agreement.Master Thesis Análise de estruturas planares para aplicações em sistemas de sensoriamento(Universidade Federal do Rio Grande do Norte, 2020-12-23) Oliveira, João Guilherme Domingos de; Silva Neto, Valdemir Praxedes da; ; http://lattes.cnpq.br/4160231554601828; ; http://lattes.cnpq.br/6182090178676621; D'Assunção, Adaildo Gomes; ; http://lattes.cnpq.br/4159638862269940; Pinheiro, Fred Sizenando Rossiter; ; http://lattes.cnpq.br/4302663615185369; Santa Cruz, Rossana Moreno; ; http://lattes.cnpq.br/2551823714869922In this work, the analysis and development of planar structures are presented, for sensing applications. The proposed sensors consist of: A log-periodic antenna modeled using traditional methods, a bio-inspired antenna in the Shiso leaf, whose scientific name is Perilla Frutescens. A complementary interdigital capacitor (CIDC) is inserted into the geometry; A microstrip antenna with circular patch with a container printed in ABS filament, the resonant element is based on the structure of complementary split-ring resonator (CSRR). The working principle of the first sensor is based on the Niscolson Ross Weir -NRW method and the last two both devices are based on the displacement of the resonant frequencies of the elements when changing the relative permissiveness of the material under test (MUT). Several simulations are carried out, so that, with the data obtained, the NRW methods were used and two empirical models are proposed. For sensors based on the resonance method to validate their effectiveness, measurements were made with dielectric substrates that have dielectric constants known in the literature. The third sensor can be applied to different types of materials, in this work it will be used to determine the percentage of water contained in different types of soils. The prototypes were built and the results obtained in the measurements were compared with the results of other studies, thus validating the effectiveness of the proposed sensors.Master Thesis Utilização de ressonadores metamateriais na melhoria de desempenho de filtros planares(Universidade Federal do Rio Grande do Norte, 2019-12-26) Silva Neto, João Alexandre da; Campos, Antônio Luiz Pereira de Siqueira; ; ; http://lattes.cnpq.br/8099257962727975; Costa, Iradilson Ferreira da; ; Rodrigues, Márcio Eduardo da Costa;This work proposes the insertion of Complementary Split-Ring Resonators (CSRR) in the planar filter ground. The intention is to improve some filter parameters found in the literature that have practical application, considering the growing demand for higher performance, smaller size, lower weight and cost of the devices that integrate the communication systems. The filters chosen were: a bandpass filter that uses Matrioska geometry for applications in the 2.45 GHz Industrial Scientific and Medical (ISM) band; and a low pass filter for digital TV applications. The idea is to insert the CSRR into the structure ground plane to increase the free attenuation of the Matrioska band-reject filter and to reduce the size of the low-pass filter. In the work the numerical and experimental results are presented, for the purpose of validation of the proposed technique. A good agreement between the results is observed, showing that the proposals presented were achieved. In the Matrioska band-reject filter, a significant improvement was obtained in the free attenuation in the filter rejection range, whereas in the low-pass filter a significant reduction in its dimensions was obtained.Doctoral Thesis Uso de ressoadores de anéis fendidos e ressoadores de anéis fendidos complementares para o melhoramento do desempenho em filtros passa-baixa em microfita(2018-06-20) Costa, Iradilson Ferreira da; Campos, Antonio Luiz Pereira de Siqueira; ; ; Gomes Neto, Alfredo; ; Vasconcelos, Cristhianne de Fátima Linhares de; ; Silva, José Patrocinio da; ; Rodrigues, Márcio Eduardo da Costa; ; Silva, Mauricio Weber Benjó da;This work presents microstrip lowpass filters with improved performance due to the insertion of Split Ring Resonators (SRR) and Complementary Split Ring Resonators (CSRR). The analysis cover three different lowpass filter configurations: steppedimpedance filters, filters using open-circuited stubs and filters using semilumped microstrip sections. The CSRR and SRR resonators have been used to enhance the rolloff and to remodel the rejection band of the filters, achieved by the removal of undesired transmission spurious bands. The improvements in these circuits have been verified by the analysis of performance parameters such as selectivity, transition bandwidth and rejection bandwidth, obtained by electromagnetic simulations and measurements of the designed microstrip lowpass filters. Values of selectivity ranging from 60 to 86 dB/GHz were achieved by the resonator-based lowpass filters. These values are considerably higher than those obtained by the conventional lowpass filters (around 6 to 38 dB/GHz). Results for rejection band from approximately 2 to 10 GHz have been obtained. The insertion of the resonators did not result in major modifications both in passband and in group delay of the analyzed filters. The lowpass filters have low order, with values from 3 to 9. In addition, a low cost dielectric substrate has been used. Though lossy, this substrate meets the intended requirements.