A theoretical and numerical approach for selecting miniaturized antenna topologies on magneto-dielectric substrates

An increasing interest is arising in developing miniaturized antennas in the microwave range. However, even when the adopted antennas dimensions are small compared with the wavelength, radiation performances have to be preserved to keep the system-operating conditions. For this purpose, magneto-dielectric materials are currently exploited as promising substrates, which allows us to reduce antenna dimensions by exploiting both relative permittivity and permeability. In this paper, we address generic antennas in resonant conditions and we develop a general theoretical approach, not based on simplified equivalent models, to establish topologies most suitable for exploiting high permeability and/or high-permittivity substrates, for miniaturization purposes. A novel definition of the region pertaining to the antenna near-field and of the associated field strength is proposed. It is then showed that radiation efficiency and bandwidth can be preserved only by a selected combinations of antenna topologies and substrate characteristics. Indeed, by the proposed independent approach, we confirm that non-dispersive magneto-dielectric materials with relative permeability greater than unit, can be efficiently adopted only by antennas that are mainly represented by equivalent magnetic sources. Conversely, if equivalent electric sources are involved, the antenna performances are significantly degraded. The theoretical results are validated by full-wave numerical simulations of reference topologies

Comparação de métodos de determinação do amortecimento estrutural através de técnicas de ajuste de curvas de funções resposta em frequência

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológio. Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2013A fenomenologia complexa dos mecanismos de amortecimento dos materiais e das estruturas impede a obtenção de modelos precisos para a predição de amortecimento da maior parte das estruturas e sistemas práticos. Isso quer dizer que, ainda hoje e na maioria das vezes, a determinação do amortecimento precisa ser feita de forma experimental, sujeita a diversas formas de erro e incertezas. Dentre as inúmeras formas de determinação de amortecimento, muitas das técnicas estão relacionadas a processos de extração de parâmetros modais que recorrem a processos de ajuste de curvas para a obtenção dos parâmetros modais. Estruturas com diferentes graus de complexidade e diferentes graus de amortecimento requerem o uso de diferentes técnicas de extração de parâmetros modais para minimizar os erros. Neste trabalho, conjuntos de dados analíticos e de simulação numérica, obtidos sob condições controladas, são utilizados para determinar a precisão dos métodos de ajuste de curvas na determinação do amortecimento estrutural. O uso de dados simulados permite calcular o erro percentual de cada um dos métodos. Por fim, dados experimentais serão utilizados para corroborar os resultados obtidos a partir dos dados controlados. Abstract: The complex phenomenology of the damping mechanisms of materials and structures is a hindrance to getting accurate models for the prediction of damping for most of structures and practical systems. This means that still today, in several cases, determination of damping must be done experimentally, subject to various forms of error and uncertainty. Among the several forms of damping determination, many of the techniques are related to methods of modal parameters extraction which use curve fitting to obtain the modal parameters. Structures with different degrees of complexity and different degrees of damping require the use of different techniques of modal parameters estimation to minimize errors. In this work sets of analytical and simulated data are obtained under controlled conditions and used to determine the accuracy of curve fitting methods to estimate the structural damping. The use of simulated data enables to calculate the percentage error of each of the methods. Lastly, experimental data will be used to corroborate the results obtained from the controlled data

Smart Wireless Power Transfer Operated by Time-Modulated Arrays via a Two-Step Procedure

The paper introduces a novel method for agile and precise wireless power transmission operated by a time-modulated array. The unique, almost real-time reconfiguration capability of these arrays is fully exploited by a two-step procedure: first, a two-element time-modulated subarray is used for localization of tagged sensors to be energized; the entire 16-element TMA then provides the power to the detected tags, by exploiting the fundamental and first-sideband harmonic radiation. An investigation on the best array architecture is carried out, showing the importance of the adopted nonlinear/full-wave computer-aided-design platform. Very promising simulated energy transfer performance of the entire nonlinear radiating system is demonstrated

Co-Design Strategies for Energy-Efficient UWB and UHF Wireless Systems

This paper reviews the most recent methods, combining nonlinear harmonic-balance-based analysis with electromagnetic (EM) simulation, for optimizing, at the circuit level, modern radiative RF/microwave systems. In order to maximize the system efficiency, each subsystem must be designed layoutwise, accounting for the presence of the others, that is, accounting for its actual terminations, rather than the ideal ones (50 Ω). In this way, the twofold goal of minimizing size and losses of the system is obtained by reducing intersystem matching networks. Indeed, terminations are complex, frequency-dispersive, and variable with the signal level, if active operations are concerned, and are responsible for performance degradation if not properly optimized. This approach is nowadays necessary, given the ever increased spread of pervasively distributed RF microsystems adopting miniaturized antennas, such as radio frequency identification (RFID) or wireless sensor networks, that must be low-cost, low-profile, low-power, and must simultaneously perform localization, identification, and sensing. For the design of a transmitter and a receiver connected with the respective antennas, suitable figures of merit are considered, encompassing radiation and nonlinear performance. Recent representative low-profile realizations, adopting ultra-wideband (UWB) excitations are used to highlight the benefit of the proposed nonlinear/EM approach for next generation energy autonomous microsystem, such as UWB-RFID tags

Characterization of surface morphology and its correlation with friction performance of brake pads

The present work presents the morphology evolution of a brake material surface submitted to braking tests through a laboratory-scale tribometer. Optical microscope images of the material’s surface were obtained for every 10 braking operations. These images were post-processed in appropriate computational software. By means of the image segmentation technique, morphological parameters related to the brake material surface were estimated. The wear rate and also the coefficient of friction resulting from the tests were measured. For the NAO material used in this study, the friction behaviour revealed to be strongly associated with the amount of contact plateaus. Besides, the mean area of the contact plateaus was the main factor responsible for increasing the real contact area of the friction material. The higher wear rate observed in the first braking operations can be mainly attributed to the higher surface roughness measured in this condition. As the braking operations progress, the plateaus becomes flatter and wear rate is reduced. Finally, the image segmentation technique proved adequate for investigating morphological aspects in friction material surface

RF Systems Design for Simultaneous Wireless Information and Power Transfer (SWIPT) in Automation and Transportation

This work presents some recent solutions that exploit the wireless power transfer (WPT) technology for energizing moving vehicles and machinery tools. Such technology is currently experiencing unprecedented interests in non-traditional RF/microwave sectors fields, such the industrial automation and the railway transportation safety. Near-field electromagnetic coupling solutions are presented showing that, in order to obtain efficient performances for broad ranges of operating conditions, the nonlinear electromagnetic co-design of the entire WPT system, from the energy source to the receiver load, needs to be carried out. This technology can be combined with wireless data transfer, thus realizing integrated systems able to simultaneously control the energy transfer and the transmission of data. The adopted operating frequencies are in the MHz range, which is only recently considered for this kind of applications. In particular this work focuses on three different systems: the first one demonstrates the constant powering of “on the move” industrial charts at 6.78 MHz, regardless of the relative position of the transmitter and the receiver sub-systems; the second one presents a novel design of a balise transportation system adopting a high efficiency GaN-based transmitter designed to keep its performance over a wide range of loading conditions; the last one consists of the simultaneous wireless power and data transfer, to a rotating machinery tool, automatically controlled by the powering system based on the coexistence of frequency-diverse inductive and capacitive couplings

IEEE Access Special Section Editorial: Wirelessly Powered Networks, and Technologies

Wireless Power Transfer (WPT) is, by definition, a process that occurs in any system where electrical energy is transmitted from a power source to a load without the connection of electrical conductors. WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including battery-less sensors, passive RF identification (RFID), passive wireless sensors, the Internet of Things and 5G, and machine-to-machine solutions. WPT-enabled devices can be powered by harvesting energy from the surroundings, including electromagnetic (EM) energy, leading to a new communication networks paradigm, the Wirelessly Powered Networks

Avaliação da resistência ao desgaste abrasivo dos revestimentos wc-10co, diamalloy® e stellite 6® depositados por hvof

A resistência ao desgaste abrasivo dos revestimentos WC-10Co (Carboneto de Tungstênio), Diamalloy® e Stellite 6®, depositados através do processo de aspersão térmica hipersônica (HVOF) sobre um substrato de aço carbono, foi avaliada através do ensaio normatizado ASTM G 65. Este método utiliza uma roda de borracha pressionada contra os corpos de prova e de areia de sílica como terceiro corpo. Os revestimentos foram caracterizados por metalografia com o objetivo de avaliar quanto à presença de poros, óxidos e partículas não fundidas. Além disso, caracterizou-se a dureza e a adesão dos revestimentos ao substrato metálico. Através dos resultados apresentados neste estudo, pode-se observar, ao final do ensaio abrasivo, que o revestimento com maior resistência ao desgaste abrasivo foi o que também apresentou maior dureza superficial

Avaliação da resistência ao desgaste abrasivo dos revestimentos wc-10co, diamalloy® e stellite 6® depositados por hvof

A resistência ao desgaste abrasivo dos revestimentos WC-10Co (Carboneto de Tungstênio), Diamalloy® e Stellite 6®, depositados através do processo de aspersão térmica hipersônica (HVOF) sobre um substrato de aço carbono, foi avaliada através do ensaio normatizado ASTM G 65. Este método utiliza uma roda de borracha pressionada contra os corpos de prova e de areia de sílica como terceiro corpo. Os revestimentos foram caracterizados por metalografia com o objetivo de avaliar quanto à presença de poros, óxidos e partículas não fundidas. Além disso, caracterizou-se a dureza e a adesão dos revestimentos ao substrato metálico. Através dos resultados apresentados neste estudo, pode-se observar, ao final do ensaio abrasivo, que o revestimento com maior resistência ao desgaste abrasivo foi o que também apresentou maior dureza superficial

A web of things approach for indoor position monitoring of elderly and impaired people

Helping, assisting and taking care of the elderly and of impaired people is one of the greatest challenges in our society. Within this paper, we propose a new approach for indoor position monitoring of people, aiming to identify in real time dangerous situations. In order to boost interoperability and continuous adaptation of the devices used, a Web Of Things based solution will be proposed and evaluated. Our contribution, in particular, consists of a portable and user friendly Radio Frequency IDentification (RFID) reader exploiting monopulse radar and beam-steering capabilities. Such hardware, exploiting a set of software modules, will be located in an environment easily accessible and extensible to a growing number of devices. The application will be the result of the cooperation between software and hardware, eventually outlining a real and completely flexible Web Of Things environment