Desenvolvimento de substrato cerâmico BiNbO4 para antenas de microfita de sistemas de comunicações sem fio

The main purpose of this work was the development of ceramic dielectric substrates of bismuth niobate (BiNbO4) doped with vanadium pentoxide (V2O5), with high permittivity, used in the construction of microstrip patch antennas with applications in wireless communications systems. The high electrical permittivity of the ceramic substrate provided a reduction of the antenna dimensions. The numerical results obtained in the simulations and the measurements performed with the microstrip patch antennas showed good agreement. These antennas can be used in wireless communication systems in various frequency bands. Results were satisfactory for antennas operating at frequencies in the S band, in the range between 2.5 GHz and 3.0 GHz.

Análise neurocomputacional de Antenas de microfita multibanda para sistemas de comunicação sem fio

This work presents a study of implementation procedures for multiband microstrip patch antennas characterization, using on wireless communication systems. An artificial neural network multilayer perceptron is used to locate the bands of operational frequencies of the antenna for different geometrics configurations. The antenna is projected, simulated and tested in laboratory. The results obtained are compared in order to validate the performance of archetypes that resulted in a good one agreement in metric terms. The neurocomputationals procedures developed can be extended to other electromagnetic structures of wireless communications systems

Análise de desempenho de sistemas de comunicação sem-fio para monitoramento de unidade de produção de poços petrolíferos terrestres

The greater part of monitoring onshore Oil and Gas environment currently are based on wireless solutions. However, these solutions have a technological configuration that are out-of-date, mainly because analog radios and inefficient communication topologies are used. On the other hand, solutions based in digital radios can provide more efficient solutions related to energy consumption, security and fault tolerance. Thus, this paper evaluated if the Wireless Sensor Network, communication technology based on digital radios, are adequate to monitoring Oil and Gas onshore wells. Percent of packets transmitted with successful, energy consumption, communication delay and routing techniques applied to a mesh topology will be used as metrics to validate the proposal in the different routing techniques through network simulation tool NS-2

Antenas e superfícies seletivas de freqüência reconfiguráveis para sistemas de comunicação sem fio

This work aims to present how the reconfigurable microstrip antennas and frequency selective surfaces can be used to operate at communication systems that require changing their operation frequency according to system requirements or environmental conditions. The main purpose is to present a reconfigurable circular microstrip antenna using a parasitic ring and a reconfigurable dipole frequency selective surface. Thereupon there are shown fundamental topics like microstrip antennas, PIN diodes and the fundamental theory of reconfigurable antennas and frequency selective surfaces. There are shown the simulations and measurements of the fabricated prototypes and it is done an analysis of some parameters like the bandwidth and radiation pattern, for the antennas, and the transmission characteristics, for the frequency selective surface. Copper strips were used in place of the diodes for proof of the reconfigurability concept

Antenas planares integradas com FSSs para aplicações em sistemas de comunicações sem fio

This work presents a theoretical and experimental analysis about the properties of microstrip antennas with integrated frequency selective surfaces (Frequency Selective Surface - FSS). The integration occurs through the insertion of the FSS on ground plane of microstrip patch antenna. This integration aims to improve some characteristics of the antennas. The FSS using patch-type elements in square unit cells. Specifically, the simulated results are obtained using the commercial computer program CST Studio Suite® version 2011. From a standard antenna, designed to operate in wireless communication systems of IEEE 802.11 a / b / g / n the dimensions of the FSS are varied to obtain an optimization of some antenna parameters such as impedance matching and selectivity in the operating bands. After optimization of the investigated parameters are built two prototypes of microstrip patch antennas with and without the FSS ground plane. Comparisons are made of the results with the experimental results by 14 ZVB network analyzer from Rohde & Schwarz ®. The comparison aims to validate the simulations performed and show the improvements obtained with the FSS in integrated ground plane antenna. In the construction of prototypes, we used dielectric substrates of the type of Rogers Corporation RT-3060 with relative permittivity equal to 10.2 and low loss tangent. Suggestions for continued work are presented

Métodos seguros para comunicação em sistemas de rede sem fio de múltiplos saltos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento de estruturas integradas de filtros e antenas para aplicações em sistemas de comunicações sem fio

This paper presents a study of the integration of filters and microstrip antennas, yielding devices named as filtennas for applications in wireless communications systems. The design of these structures is given from the observation of filtennas based integration between horn antennas and frequency selective surfaces (FSS), used in the band X. The choice of microstrip line structures for the development of a new configuration filtennas justifies the wide application of these transmission lines, in recent decades, always resulting in the production of circuit structures with planar light-weight, compact size, low cost, easy to construct and particularly easy to integrate with other microwave circuits. In addition, the antenna structure considered for the composition of filtennas consists of a planar monopole microstrip to microstrip filters integrated in the feed line of the antenna. In particular, are considered elliptical monopole microstrip (operating in UWB UWB) microstrip filters and (in structures with associated sections in series and / or coupled). In addition, the monopole microstrip has a proper bandwidth and omnidirectional radiation pattern, such that its integration with microstrip filters results in decreased bandwidth, but with slight changes in the radiation pattern. The methods used in the analysis of monopoles, and filters were filtennas finite elements and moments by using commercial software Ansoft Designer and HFSS Ansoft, respectively. Specifically, we analyze the main characteristics of filtennas, such as radiation pattern, gain and bandwidth. Were designed, constructed and measures, several structures filtennas, for validation of the simulated results. Were also used computational tools (CAD) in the process of building prototypes of planar monopoles, filters and filtennas. The prototypes were constructed on substrates of glass-fiber (FR4). Measurements were performed at the Laboratory for Telecommunications UFRN. Comparisons were made between simulated and measured, and found good agreement in the cases considered

Mestre em Sistemas e Computação

In this work will applied the technique of Differential Cryptanalysis, introduced in 1990 by Biham and Shamir, on Papílio s cryptosystem, developed by Karla Ramos, to test and most importantly, to prove its relevance to other block ciphers such as DES, Blowfish and FEAL-N (X). This technique is based on the analysis of differences between plaintext and theirs respective ciphertext, in search of patterns that will assist in the discovery of the subkeys and consequently in the discovery of master key. These differences are obtained by XOR operations. Through this analysis, in addition to obtaining patterns of Pap´ılio, it search to obtain also the main characteristics and behavior of Papilio throughout theirs 16 rounds, identifying and replacing when necessary factors that can be improved in accordance with pre-established definitions of the same, thus providing greater security in the use of his algoritm

Camada de gerenciamento para comunicação entre computadores baseada em redes sem fio (WSE-OS)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Middleware de comunicação entre objetos distribuídos para gerenciamento de computadores baseado em redes sem fio (WSE-OS)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Codificação de canais em sistemas de comunicação sem fio baseado em reticulados

Pós-graduação em Engenharia Elétrica - FEIS

Sobre o uso de sistemas de computação algébrica na solução de problemas de mecânica das estruturas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Simulação de sistemas de computação em nuvem para o iSPD

O uso de computação em nuvem tem se tornado cada vez mais intenso nos últimos anos. Devido principalmente a fatores econômicos, a avaliação de desempenho de sistemas de computação em nuvem, principalmente através de simulação, tem sido amplamente aplicada. Neste trabalho se apresenta a inclusão da funcionalidade de modelagem e simulação de computação em nuvem no simulador de ambientes distribuídos iSPD.

Wimax e os efeitos disruptivos na indústria das telecomunicações

Wireless é broadband que entrega applicações e serviços de comunicações avançadas a qualquer momento e em qualquer lugar. A evolução das tecnologias e das applicações está alterando, também, a linha tradicional que definia e separava aplicações, serviços e redes. Em conseqüência, os limites funcionais que definem as ferramentas dominantes de nosso tempo, tais como o PC, a TV, o telefone móvel e o telefone das comunicações, estão, também, desaparecendo. Esta convergência foi. porém, limitada pelo bandwith, gerando limitações que estão associadas com às comunicações e à infraestrutura wireless. As potencialidades técnicas da tecnologia de WIMAX permitirão que os fornecedores de serviço possam finalmente oferecer a voz, os dados, o móbil e os serviços de entretenimento em redes únicas de telecomunicação broadband wireless. Sem dúvida, esta convergência wireless alterará dramaticamente a indústria.

Proposta e modelagem de comunicação segura para redes veiculares (VANETS)

Pós-graduação em Ciência da Computação - IBILCE