Navegando por Assunto "Waveguides"

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Acesso aberto (Open Access)
Aplicação da teoria de grupos magnéticos para guias de onda e cavidades ressonantes com meios magnéticos
(Universidade Federal do Pará, 2014-08-27) BEIRÃO, Antonio Thiago Madeira; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
In this paper we apply the theory of magnetic groups in cross sections of waveguides square, rectangular and circular filled with ferrite or semiconductor material with different types of magnetization. These wave guides are structures used in microwave technology as phase shifters, cut-off switches and insulators. Similarly as done in waveguides with different symmetries, were analyzed and classified also resonant cavities with cubic and cylindrical paralelepípeda geometries using group theory magnetic. Considering waveguide sections with four doors and using group theory methods calculated to scattering matrix structure for these guides with different Symmetries and are discussed some of its properties. Furthermore, scattering matrices obtained TE0n modes are accurate and, from them, were calculated eigenvalues and eigenvectors of matrices. The results serve as theoretical reference to check the accuracy of numerical calculations in structures of waveguides.
Acesso aberto (Open Access)
Avaliação de modos guiados em cabos de cobre para transmissão de dados em terabit por segundo
(Universidade Federal do Pará, 2020-03-27) SOUZA, Daynara Dias; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Copper-based technologies have used twisted pair and coaxial cables as transmission lines, exploring TEM (Transverse Electromagnetic) mode to transmit data. In twisted pair technology, to ensure higher rates, it is necessary to increase the band frequencies, which also implies an increase in attenuation over the TEM mode, with a consequent limit on the link data rate. Applications for the latest generation (5G) systems require rates in the order of tens Gbps (Gigabit per second), practically impossible to meet due to their attenuation, even considering short links. In this context, to give a new breath to twisted pair cables, it was proposed to use them as waveguides, i.e., exploring their higher-order modes for transmission, in a system called Terabit DSL (Digital Subscriber Line). Such modes are of the TE (Transverse Electric) or TM (Transverse Magnetic) types, and arise when the wavelengths, associated to the operating frequencies, are of the same order or smaller than the cross-sectional dimensions of the twisted pair cable. A similar fact applies to coaxial cables. When using these modes, it is estimated transmission rates in the order of Tbps (Terabit per second) to be achieved on twisted pair cables. This enables, for example, to have twisted pair and coaxial cables as viable alternatives to the transport network in the future 5G system. Such predictions assume that the model based on the guided mode on a single bare conducting wire, known as the Sommerfeld model, describes the attenuation of the higher-order guided modes in a twisted pair. However, this model does not adequately describe twisted pair cables, given that its physical structure is much more complex. Therefore, a more accurate study on the characteristics of the higher-order modes present in twisted pair and coaxial cables is needed, aiming at predictions in complete agreement with the real structure and electromagnetic propagation through them. This work investigates the propagation of several guided modes in twisted pair and coaxial cables, from numerical simulations in the HFSS (High Frequency Structure Simulator) software, considering real constructive characteristics. Based on the results obtained, the aggregate data rate of each cable used as a waveguide was determined. The results obtained indicate that data rates of more than 1.7 Tbps in just one twisted pair can be reached for 10 meters in length, up to 6.1 Tbps in one cable with four twisted pairs and approximately 5.6 Tbps in one coaxial cable.
Acesso aberto (Open Access)
Estudo de fibras porosas com inclusões metálicas para guiamento em THz
(Universidade Federal do Pará, 2017-09-08) CARDOSO, Markos Paulo; SILVA, Anderson Oliveira; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The guidance of THz waves has been found of great importance to improve the performance of spectroscopy, imaging and sensing setups. One of the major challenges in designing such structures is the mitigation of the high losses presented by dielectric media in the THz spectral range (0.1 up to 10 THz). This work performs an analytical and numerical modeling of porous fibers with gold inclusions for THz guidance. The design of these metal-dieletric interface is capable to confine THz waves in the air region of the porous fiber, through the excitation of surface plasmons, modes that result from the resonant interaction between the incident electromagnetic radiation and the collective oscillation of free electrons on the metal surface. It is shown that from a suitable design of the gold layer, the effective losses can be reduced and a zero chromatic dispersion can be achieved as result of the coupling between the fiber modes and the surfasse plasmons.
Acesso aberto (Open Access)
Filtro eletromagnético baseado em grafeno operando na região THz.
(Universidade Federal do Pará, 2024-04-04) SANTOS, Luis Eduardo de Sena dos; CASTRO, Wagner Ormanes Palheta; http://lattes.cnpq.br/4322608238580829; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
In this study, a compact nanoscale plasmonic filter was proposed and numerically analyzed. The plasmonic filter is based on graphene nanoribbons coupled to a disc-shaped graphene resonator with horizontal side cuts and 45o orientation, deposited on a dielectric substrate of silica (SiO2) and silicon (Si) , operating in the THz region. We investigated simple structures that allow tuning the resonance frequency of the resonator. This work provides a viable solution for graphene plasmonic nanofilter structures for future use in highly integrateds plasmonic device applications in THz and FIR regions.