A natureza vibratória, oriunda da transferência energética, manifesta-se em todos os sistemas e estruturas. Na engenharia, essa transferência energética se revela como um fenômeno vibratório indesejável ou desejável. Em sistemas mecânicos, o controle dinâmico para mitigação de vibrações indesejáveis se realiza através de diversas técnicas e configurações, entre os mais usuais, o Amortecedor de Massa Sintonizável (AMS). No entanto, sabe-se que seu desempenho é suscetível a alterações nas frequências de operação e na natureza das excitações. Em sistemas elétricos, as vibrações do ambiente podem ser desejáveis e convertidas em energia elétrica útil para a realimentação de rede de sensores sem fio e computação pervasiva. A fim de combinar estes fenômenos e reduzir custos de operação, é necessário projetar dispositivos sintonizáveis robustos capazes de operar eficientemente em uma banda larga de frequências. Portanto, este trabalho visa projetar e analisar experimentalmente um atenuador de vibrações eletromagnético sintonizável (semi-ativo) com captação energética (AEMSCE) através da introdução deliberada de não linearidades. O AEMSCE consiste em um sistema massa-mola-amortecedor não linear com um ímã oscilante central orientado sob forças repulsivas magnéticas e uma bobina instalada, sendo capaz de dissipar as vibrações da estrutura e convertê-las em energia elétrica útil. Os recursos e parâmetros do AEMSCE são apresentados e identificados. O fator de transdução eletromagnético que acopla o sistema mecânico ao elétrico é quantificado. Mostra-se que a variação da distância entre ímãs promove ao sistema ressonância ajustável e que a força de restauração magnética resultante apresenta uma faixa de operação linear. No trabalho, verifica-se que o campo de máxima captação energética está contido na faixa de operação linear confirmando a relevância deste campo linear. O comportamento do sistema é analisado considerando as influências da força restauradora magnética, das forças amortecidas e da força de atrito. A partir dessas análises e das aproximações realizadas, apresenta-se estratégias de controle passivas e técnicas de otimização para mitigação, cuja resultante é um campo de atenuação ótimo, assim como desenvolve-se métodos de otimalidade para maximizar a conversão energética do AEMSCE, cuja resultante é um amortecimento elétrico ótimo ou um amortecimento admissível ótimo (deslocamento máximo). Métodos analíticos e simulações numéricas são desenvolvidos em todo o trabalho com diferentes configurações para analisar a robustez e eficiência do dispositivo, através do comportamento dinâmico vibratório à resposta transiente e estacionária induzido por excitação de base harmônica. De maneira geral, os resultados mostram que os parâmetros de sintonia e amortecimento do AEMSCE podem ser combinados e ajustados para ampliar o controle de vibrações da estrutura e maximizar a captação energética, principalmente na ressonância. Verifica-se que existe uma relação de importância da tensão induzida e do amortecimento elétrico, através da variação da resistência de carga no resistor, com a atenuação e captação energética. Por fim, este trabalho buscou apresentar os melhores métodos e resultados de parâmetros de amortecimento a fim de obter informações como guia de projeto para otimizar os dispositivos futuros e para a proposição de incorporar um controle semiativo ao AEMSCE. Como forma de melhorar o desempenho em aplicações futuras, é possível combinar as propriedades ótimas resultantes e ajustá-las através de estratégias de controle semiativa, explorando a dinâmica linear e não linear do sistema. / Vibratory nature, derived from the energy transfer, manifests itself in all systems and structures. In engineering, this energy transfer is revealed as an undesirable or desirable vibrational phenomenon. In mechanical systems, the dynamic control to mitigate undesirable vibrations is achieved through several techniques and configurations, among the most usual, the Tunable Mass Damper (TMD). However, it is known that their performance is susceptible to changes in the operating frequencies and the nature of the excitations. In electrical systems, ambient vibrations may be desirable and converted into useful electrical energy for the feedback of wireless sensors network and pervasive computing. In order to combine these phenomena and reduce operating costs, it is necessary to design robust tunable devices capable of operating efficiently over a wide frequency band. Therefore, this work aims to design and experimentally analyze a tunable electromagnetic vibrations absorver (semi-active) with energy harvesting (TEMAEH) through the deliberated introduction of non-linearities. TEMAEH consists of a non-linear mass-spring-damper system with a central oscillating magnet oriented under magnetic repulsive forces and a coil installed, being able to dissipate vibrations of the structure and convert them into useful electrical energy. The TEMAEH features and parameters are presented and identified. Electromagnetic transduction factor that couples the mechanical to electrical system is quantified. It is shown that the variation of the distance between magnets provides adjustable resonance to the system and that the resulting magnetic restoring force has a linear operating range. In the work, it is verified that the field of maximum energy harvesting is contained in the linear operating range confirming the relevance of this linear field. The behavior of the system is analyzed considering the influences of magnetic restoring force, damped forces and frictional force. From these analyzes and the approximations performed, passive control strategies and optimization techniques for mitigation are presented, resulting in an optimum attenuation field, as well as optimization methods to maximize the energy conversion of the TEMAEH, resulting in an optimum electric damping or optimum permissible damping (maximum displacement). Analytical methods and numerical simulations are developed throughout the work with different configurations to analyze the robustness and efficiency of the device through the dynamic behavior of vibration to the transient and stationary response induced by harmonic based excitation. In general, the results show that the tuning and damping parameters of the TEMAEH can be combined and adjusted to increase the vibration control of the structure and to maximize energy harvesting, especially in resonance. It is verified that there is a relation of importance of the induced voltage and the electrical damping, through the variation of the load resistance in the resistor, with the attenuation and power generation. Finally, this work sought to present the best methods and results of damping parameters in order to obtain information as a project guide to optimize future devices and for the proposition to incorporate a semiative control to TEMAEH. As a way to improve performance in future applications, it is possible to combine the resulting optimal properties and adjust them through semiative control strategies, exploring the linear and non-linear dynamics of the system.

THz and mm-wave technology has become increasingly significant in a very diverse range of applications such as spectroscopy, imaging, and communication as a consequence of a plethora of significant advances in this field. However to achieve a mass production of THz systems, all the commercial aspects should be considered. The main concerns are attributed to the robustness, compactness, and a low cost device. In this regard, research efforts should be focused on the elimination of obstacles standing in the way of commercializing the THz technology. To this end, in this study, low cost fabrication technologies for various parts of mm-wave/THz systems are investigated and explored to realize compact, integrated, and rugged components. This task is divided into four phases. In the first phase, a robust fiber-based beam delivery configuration is deployed instead of the free beam optics which is essential to operate the low cost THz photomixers and photoconductive antennas. The compensation of different effects on propagation of the optical pulse along the optical fiber is achieved through all-fiber system to eliminate any bulky and unstable optical components from the system. THz measurements on fiber-coupled systems exhibit the same performance and even better compared to the free beam system. In the next phase, the generated THz wave is coupled to a rectangular dielectric waveguide through design of a novel transition with low insertion loss. The structure dimensions are reported for various range of frequencies up to 650GHz with insertion loss less than 1dB. The structure is fabricated through a standard recipe. In third phase, as consequence of the advent of high performance active device at mm-wave and THz frequency, a transition is proposed for coupling the electromagnetic wave to the active devices with CPW ports. Different approaches are devised for different frequencies as at higher frequencies any kind of metallic structure can introduce a considerable amount of loss to the system. The optimized structures show minimum insertion loss as low as 1dB and operate over 10% bandwidth. The various configurations are fabricated for lower frequencies to verify the transition performance. The last phase focuses on the design, optimization, fabrication and measurements of a new dielectric side-grating antenna for frequency scanning applications. The radiation mechanism is extensively studied using two different commercial full-wave solvers as well as the measured data from the fabricated samples. The optimized antenna achieves a radiation efficiency of 90% and a gain of 18dB. The measured return loss and radiation pattern show a good agreement with the simulation results.

THz and mm-wave technology has become increasingly significant in a very diverse range of applications such as spectroscopy, imaging, and communication as a consequence of a plethora of significant advances in this field. However to achieve a mass production of THz systems, all the commercial aspects should be considered. The main concerns are attributed to the robustness, compactness, and a low cost device. In this regard, research efforts should be focused on the elimination of obstacles standing in the way of commercializing the THz technology. To this end, in this study, low cost fabrication technologies for various parts of mm-wave/THz systems are investigated and explored to realize compact, integrated, and rugged components. This task is divided into four phases. In the first phase, a robust fiber-based beam delivery configuration is deployed instead of the free beam optics which is essential to operate the low cost THz photomixers and photoconductive antennas. The compensation of different effects on propagation of the optical pulse along the optical fiber is achieved through all-fiber system to eliminate any bulky and unstable optical components from the system. THz measurements on fiber-coupled systems exhibit the same performance and even better compared to the free beam system. In the next phase, the generated THz wave is coupled to a rectangular dielectric waveguide through design of a novel transition with low insertion loss. The structure dimensions are reported for various range of frequencies up to 650GHz with insertion loss less than 1dB. The structure is fabricated through a standard recipe. In third phase, as consequence of the advent of high performance active device at mm-wave and THz frequency, a transition is proposed for coupling the electromagnetic wave to the active devices with CPW ports. Different approaches are devised for different frequencies as at higher frequencies any kind of metallic structure can introduce a considerable amount of loss to the system. The optimized structures show minimum insertion loss as low as 1dB and operate over 10% bandwidth. The various configurations are fabricated for lower frequencies to verify the transition performance. The last phase focuses on the design, optimization, fabrication and measurements of a new dielectric side-grating antenna for frequency scanning applications. The radiation mechanism is extensively studied using two different commercial full-wave solvers as well as the measured data from the fabricated samples. The optimized antenna achieves a radiation efficiency of 90% and a gain of 18dB. The measured return loss and radiation pattern show a good agreement with the simulation results.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.