Navegando por Assunto "TV digital"

Agora exibindo 1 - 4 de 4

Acesso aberto (Open Access)
Avaliação da tecnologia femtocell como canal de retorno para TV digital
(Universidade Federal do Pará, 2013-08-26) COSTA, Allan Barbosa; CARDOSO, Diego Lisboa; http://lattes.cnpq.br/0507944343674734; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
Traffic measurement on Digital TV interactive applications for fourth generation networks, especially WiMAX and femtocell, has been a challenge to researchers around the world. The traffic pattern of an interactive application on the Brazillian System of Digital TV (SBTVD) was identified. Simulations on a wireless network were carried out using data obtained of traffic analysis. In this work a WiMAX and a femtocell network were chosen to simulate the return channel of a Digital TV application on a WMAN (Wireless Metropolitan Area Network). In order to reduce signal attenuation, femtocell arises as a promising solution, reducing macrocell usage, as femtocells cover indoor environments. The simulations is this work were executed using OPNET software. Through them it is possible to estimate the feasibility of femtocell and WiMAX technologies as return channel for Digital TV.
Acesso aberto (Open Access)
Modelo de rádio propagação em UHF para ambientes não homogêneos e climas distintos utilizando técnica de aprendizagem de máquina
(Universidade Federal do Pará, 2015-08-20) GOMES, Cristiane Ruiz; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
The digital TV broadcasts have greatly increased worldwide in recent years, especially in Brazil. The establishment and improvement of these transmission systems rely on models that take into account, among other factors, the geographical characteristics of the region, as these contribute to signal degradation. In Brazil, there is a great diversity of scenery and climates. For years several propagation models have been studied many for several frequency bands and types of paths. This thesis proposes an outdoor empirical radio propagation model for UHF band, which is used in digital TV. The proposed model estimates received power values can be applied to non-homogeneous paths and different climates, this latter presents innovative character for the UHF band. Different artificial intelligence techniques were chosen for theoretical and computational basis for having the ability to introduce, organize and describe quantitative and qualitative data quickly and efficiently, making it possible to determine the received power in a variety of settings and climates. The proposed model was applied to a city in the Amazon region with heterogeneous paths and wooded urban areas, fractions of freshwater among others. Measurement campaigns were conducted to obtain data signals from two digital TV stations in the metropolitan area of the city of Belém-Pará to model, compare and validate the model. The results are consistent. The model depicts a distinct difference between the two seasons of the studied year and small RMS errors for all cases studied. The validation of the model was based on the comparison with empirical and deterministic models.
Acesso aberto (Open Access)
Predição de campo elétrico para TV digital usando Funções de Green diádicas
(Universidade Federal do Pará, 2014-07-01) SILVA, Diego Kasuo Nakata da; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
This work provides a method for the prediction of electric field intensity to Digital TV using the Dyadic Green's function. The Dyadic is a powerful mathematical tool which has symbolic simplicity and robustness, thus enabling some characteristics of the medium (such as permittivity, conductivity and permeability, for example) are considered in developing the electric field model, as well as take into account the anisotropy of the medium. In most related works using the dyadic Green's functions are related in the VHF band. This work will present from basic concepts of dyadic, developing it for the calculation of a model which can predict the electric field to the UHF band, in which systems are Digital TV. A theoretical explanation and mathematical development will be made such that a clear understanding and objective are achieved in the study of dyadic Green's functions, in a part of the theory of electromagnetism Tests were performed to confirm the applicability of the suggested formulation, making simulations that perform a comparison between measured data, from two TV stations located in the city of Belém, and the Okumura-Hata model modified, showing satisfactory results for both frequencies in VHF and UHF.
Acesso aberto (Open Access)
Projeto de um monopolo Hi para aplicações no sistema brasileiro de TV digital
(Universidade Federal do Pará, 2013-01-04) ALCÂNTARA NETO, Miércio Cardoso de; BARROS, Fabrício José Brito; http://lattes.cnpq.br/9758585938727609; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
This research deals with the design and analysis of a planar monopole antenna with modified geometry aiming its use for signal reception of digital TV in Brazil working in the of 470 MHz to 806 MHz. Track this contained in the spectrum of UHF-Ultra High Frequency (300 MHz to 3 GHz). To develop this work was taken as reference the antenna called "The Hi Monopole". What originally was presented to operate in UWB (Ultra Wide Band) at 3.1 to 10.6 GHz. For the development of the proposed work, different techniques of adjustment of the antenna can be used for broadband operation, such as: changes in the structure of antenna, resistive loading, switching, using of parasitic elements and matching structures. The design of broadband antennas can be made from three different approaches: time domain, frequency domain and expansion for singularities method. The frequency domain method was employed in this work to the antenna design proposed, some of the techniques mentioned above were analyzed aiming to increase bandwidth, and made a prototype of the antenna to validate the concepts employed. The antenna was designed for the range of 470 MHz to 890 MHz. the prototype built for this same range presented good results, which validates the technique employed. Positive and negative aspects of use of this technique are discussed throughout the work. The commercial computer program CST® MICROWAVE STUDIO, based on the Finite Integration Technique (FIT) was used for simulations in frequency domain.