Estudo e aplicação de guias de ondas integrados ao substrato em frequências de micro-ondas.

Esse trabalho de pesquisa apresenta um estudo detalhado sobre guias de ondas integrados ao substrato (SIW) operando em frequências de micro-ondas com base na teoria de guias de ondas retangulares (RWG). O estudo sobre guias SIW associa equações apresentadas na literatura e utiliza simulações eletromagnéticas para desenvolver um procedimento de projeto bem definido. É considerada a integração entre guias SIW e linhas de transmissão de microfita, projetando-se transições entre essas duas estruturas com o propósito de prover casamento de impedância e de viabilizar a caracterização em frequências de micro-ondas. São apresentadas considerações sobre processos de fabricação de circuitos SIW em substratos constituídos por laminados de alta frequência. Uma vez estabelecidos os procedimentos de fabricação e os critérios de projeto, a tecnologia SIW é aplicada ao projeto de três guias de ondas SIW nas bandas S e X, que foram fabricados empregando laminados de alta-frequência. Foram projetados dois filtros SIW passa-faixa empregando cavidades ressonantes e postes metálicos indutivos. Os dois filtros operam na frequência central de 10,61 GHz, sendo que um deles tem banda de passagem de 7,5%e é de 3ª ordem e o outro filtro tem banda de passagem de 15%, sendo de 5ª ordem. Foram realizadas comparações entre o desempenho simulado e experimental das estruturas SIW projetadas. Os resultados de simulações eletromagnéticas e experimentais demonstraram boa concordância. Os projetos em tecnologia SIW apresentados neste trabalho de pesquisa possuem perdas de retorno melhores que 10 dB na banda de operação e perdas por inserção de 1,0 dB a 1,5 dB. É apresentada a análise da sensibilidade do desempenho dos guias de ondas e filtros SIW projetados a desvios dimensionais típicos do processo de fabricação por microfresagem mecânica. Com os resultados experimentais e de simulação foi possível validar os procedimentos de projeto e de fabricação de circuitos SIW operando em frequências de micro-ondas.

Theory of ferromagnetism in planar heterostructures of (Mn,III)-V semiconductors

A density-functional theory of ferromagnetism in heterostructures of compound semiconductors doped with magnetic impurities is presented. The variable functions in the density-functional theory are the charge and spin densities of the itinerant carriers and the charge and localized spins of the impurities. The theory is applied to study the Curie temperature of planar heterostructures of III-V semiconductors doped with manganese atoms. The mean-field, virtual-crystal and effective-mass approximations are adopted to calculate the electronic structure, including the spin-orbit interaction, and the magnetic susceptibilities, leading to the Curie temperature. By means of these results, we attempt to understand the observed dependence of the Curie temperature of planar δ-doped ferromagnetic structures on variation of their properties. We predict a large increase of the Curie temperature by additional confinement of the holes in a δ-doped layer of Mn by a quantum well.

Three-dimensional planar model estimation using multi-constraint knowledge based on k-means and RANSAC

Plane model extraction from three-dimensional point clouds is a necessary step in many different applications such as planar object reconstruction, indoor mapping and indoor localization. Different RANdom SAmple Consensus (RANSAC)-based methods have been proposed for this purpose in recent years. In this study, we propose a novel method-based on RANSAC called Multiplane Model Estimation, which can estimate multiple plane models simultaneously from a noisy point cloud using the knowledge extracted from a scene (or an object) in order to reconstruct it accurately. This method comprises two steps: first, it clusters the data into planar faces that preserve some constraints defined by knowledge related to the object (e.g., the angles between faces); and second, the models of the planes are estimated based on these data using a novel multi-constraint RANSAC. We performed experiments in the clustering and RANSAC stages, which showed that the proposed method performed better than state-of-the-art methods.

Three-dimensional planar object tracking with sub-pixel accuracy

Subpixel techniques are commonly used to increase the spatial resolution in tracking tasks. Object tracking with targets of known shape permits obtaining information about object position and orientation in the three-dimensional space. A proper selection of the target shape allows us to determine its position inside a plane and its angular and azimuthal orientation under certain limits. Our proposal is demonstrated both numerical and experimentally and provides an increase the accuracy of more than one order of magnitude compared to the nominal resolution of the sensor. The experiment has been performed with a high-speed camera, which simultaneously provides high spatial and temporal resolution, so it may be interesting for some applications where this kind of targets can be attached, such as vibration monitoring and structural analysis.

A study of the non-uniform convergence of the inverse of a doubly-infinite matrix associated with a boundary value problem in a waveguide /

"Contract AF33(616)-6079 Project No. 9-(13-6278), Task No. 40572. Sponsored by: Aeronautical Systems Division"

Closely spaced transverse slots in rectangular waveguide /

"Contract AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development Center"

Coupling of antenna elements to a circular surface waveguide /

"Contract No. AF33(616)-310 RDO No. R-112-110 SR-6f2"

The finite range Wiener-Hopf integral equation and a boundary value problem in a waveguide /

"Contract No. AF33(616)-6079 Project No. 9-(13-6278) Task 40572. Sponsored by: Wright Air Development Center"

Impedance properties of complementary multiterminal planar structures /

"Contract AF33(616)-6079 Project No. 9-(13-6278) Task 40572. Sponsored by: Wright Air Development Center"

Non-planar logarithmically periodic antenna structures /

"Contract AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development"

Coupled waveguide excitation of traveling wave slot antennas /

"Contract No. AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development Center"

A planar geometrical model for representing multidimensional discrete spaces and multiple-valued logic functions /

Bibliography: p. 37-38.

Shower development and heating in the waveguide structure with an 800 Mev electron beam /

AEC Contract AT(04-3)-400.

Optical waveguide communications glossary /

Mode of access: Internet.