Neste trabalho é realizada a otimização de antena de microfita banda larga de formato E utilizando o método de Diferenças Finitas no Domínio do Tempo (FDTD). Um programa desenvolvido em C é usado para analisar e aperfeiçoar a antena em projeto, tamanho, largura de banda e polarização. Inicialmente é feita a introdução sobre o assunto, abordando aspectos de comunicações e de antenas de microfita, além de se fazer revisão bibliográfica e resumir o estado da arte sobre o tema do trabalho. O próximo item, visando a sistematizar o projeto da antena, é a caracterização da antena de formato E, obtida ao variar seus parâmetros e verificar o desempenho por meio da análise do comportamento das freqüências que compõem a largura de banda. O trabalho prossegue com simulações numéricas e medidas da largura de banda, do ganho, dos níveis de polarização e da eficiência da antena. A tese é concluída com observações sobre o analisado e sugestões para prosseguimento e aperfeiçoamento das investigações técnicas realizadas. / The optimization of wideband E-format microstrip antenna employing the Finite Difference Time Domain (FDTD) method is shown in this work. This developed software is used to optimize different design parameters and characteristics of the antenna, such the dimensions, the bandwidth, the input impedance and the polarization. Firstly, an introduction considering the main issues related to wireless communications and antennas is done. Then, a review of the wideband antennas theory and conventional methods to the antenna analysis, with emphasis on the FDTD method, are described. The following topic is a parametric study, where the antenna parameters are being changed and performance variations are considered. Next, simulations using the FDTD method and measurements are compared and the relevant characteristics are optimized, e.g., in terms of dimensions, bandwidth, input impedance, gain, efficiency and polarization. Finally, the main contributions and conclusion of this thesis are described and some suggestions for further works are presented.

Neste trabalho é realizada a otimização de antena de microfita banda larga de formato E utilizando o método de Diferenças Finitas no Domínio do Tempo (FDTD). Um programa desenvolvido em C é usado para analisar e aperfeiçoar a antena em projeto, tamanho, largura de banda e polarização. Inicialmente é feita a introdução sobre o assunto, abordando aspectos de comunicações e de antenas de microfita, além de se fazer revisão bibliográfica e resumir o estado da arte sobre o tema do trabalho. O próximo item, visando a sistematizar o projeto da antena, é a caracterização da antena de formato E, obtida ao variar seus parâmetros e verificar o desempenho por meio da análise do comportamento das freqüências que compõem a largura de banda. O trabalho prossegue com simulações numéricas e medidas da largura de banda, do ganho, dos níveis de polarização e da eficiência da antena. A tese é concluída com observações sobre o analisado e sugestões para prosseguimento e aperfeiçoamento das investigações técnicas realizadas. / The optimization of wideband E-format microstrip antenna employing the Finite Difference Time Domain (FDTD) method is shown in this work. This developed software is used to optimize different design parameters and characteristics of the antenna, such the dimensions, the bandwidth, the input impedance and the polarization. Firstly, an introduction considering the main issues related to wireless communications and antennas is done. Then, a review of the wideband antennas theory and conventional methods to the antenna analysis, with emphasis on the FDTD method, are described. The following topic is a parametric study, where the antenna parameters are being changed and performance variations are considered. Next, simulations using the FDTD method and measurements are compared and the relevant characteristics are optimized, e.g., in terms of dimensions, bandwidth, input impedance, gain, efficiency and polarization. Finally, the main contributions and conclusion of this thesis are described and some suggestions for further works are presented.

In this thesis, the applicability of Class-D amplifiers to integrated wide-band communication line driver applications is studied. While Class-D techniques can address some of the efficiency limitations of linear amplifier structures and have shown promising results in low frequency applications, the low frequency techniques and knowledge need further development in order to improve their practicality for wide band systems. New structures and techniques to extend the application of Class-D to wide-band communication systems, in particular the HomePlug AV wire- line communication standard, will be proposed. Additionally, the digital processing requirements of these wide-band systems drives rapid movement towards nanometer technology nodes and presents new challenges which will be addressed, and new opportunities which will be exploited, for wide-band integrated Class-D line drivers. There are three main contributions of this research. First, a model of Class-D efficiency degradation mechanisms is created, which allows the impact of high-level design choices such as supply voltage, process technology and operating frequency to be assessed. The outcome of this section is a strategy for pushing the high efficiency of Class-D to wide band communication applications, with switching frequencies up to many hundreds of Megahertz. A second part of this research considers the design of efficient, fast and high power Class-D output stages, as these are the major efficiency and bandwidth bottleneck in wide-band applications. A novel NMOS-only totem pole output stage with a fast, integrated drive structure will be proposed. In a third section, a complete wide-band Class-D line driver is designed in a 0.13μm digital CMOS process. The line driver is systematically designed using a rigorous development methodology and the aims are to maximise the achievable signal bandwidth while minimising power dissipation. Novel circuits and circuit structures are proposed as part of this section and the resulting fabricated Class-D line driver test chip shows an efficiency of 15% while driving a 30MHz wide signal with an MTPR of 22dB, at 33mW injected power.

Neste trabalho é realizada a otimização de antena de microfita banda larga de formato E utilizando o método de Diferenças Finitas no Domínio do Tempo (FDTD). Um programa desenvolvido em C é usado para analisar e aperfeiçoar a antena em projeto, tamanho, largura de banda e polarização. Inicialmente é feita a introdução sobre o assunto, abordando aspectos de comunicações e de antenas de microfita, além de se fazer revisão bibliográfica e resumir o estado da arte sobre o tema do trabalho. O próximo item, visando a sistematizar o projeto da antena, é a caracterização da antena de formato E, obtida ao variar seus parâmetros e verificar o desempenho por meio da análise do comportamento das freqüências que compõem a largura de banda. O trabalho prossegue com simulações numéricas e medidas da largura de banda, do ganho, dos níveis de polarização e da eficiência da antena. A tese é concluída com observações sobre o analisado e sugestões para prosseguimento e aperfeiçoamento das investigações técnicas realizadas. / The optimization of wideband E-format microstrip antenna employing the Finite Difference Time Domain (FDTD) method is shown in this work. This developed software is used to optimize different design parameters and characteristics of the antenna, such the dimensions, the bandwidth, the input impedance and the polarization. Firstly, an introduction considering the main issues related to wireless communications and antennas is done. Then, a review of the wideband antennas theory and conventional methods to the antenna analysis, with emphasis on the FDTD method, are described. The following topic is a parametric study, where the antenna parameters are being changed and performance variations are considered. Next, simulations using the FDTD method and measurements are compared and the relevant characteristics are optimized, e.g., in terms of dimensions, bandwidth, input impedance, gain, efficiency and polarization. Finally, the main contributions and conclusion of this thesis are described and some suggestions for further works are presented.

The application of nanowires (NWs) in solar cells (SCs) is of great interest due to their new promising aspects established in nanoelectronics. Semiconductors associated with plasmonic metal nanoparticles (NPs) such as Silver (Ag), Gold (Au) and Copper (Cu), show enhanced performance in solid state light absorbing SCs owing to plasmonic characteristic of noble metal NPs. Plasmonic NPs presented a significant role in development of visible light harvesting for many applications such as photocatalytic materials, photodynamic in Surface Enhanced Raman Spectroscopy (SERS) and photovoltaics (PVs). Integration of plasmonic NPs in semiconductor materials have opened the routes to expand new PV systems with high efficiency light absorption. In this project, we introduce the synthesis ZnO and TiO2 NWs used as N-type semiconducting substrates and various methods for isolating plasmonic metal NPs, which are later deposited on the semiconducting substrates. Vertically aligned ZnO and TiO2 NWs arrays were grown on the fluorine-doped tin oxide (FTO) conductive glass substrates via hydrothermal method at low temperature and the plasmonic NPs were synthesized by wet chemistry procedures and finally decorated on the NW films by using electrophoretic deposition.  The impact of metal NPs loaded on the ZnO and TiO2 NWs substrates was studied by means of UV-vis spectroscopy and Photoluminescence (PL) spectroscopy. The absorbance spectra of individual NPs were recorded. Remarkably, the reflectance spectra of produced samples presented an enhancement in light absorption of the substrates after uptake of NPs on the ZnO and TiO2 NWs. The optical properties of the as grown ZnO NWs films decorated with Ag NPs (I) in direct contact with substrate and (II) in presence of an Al2O3 insulating spacer layer have been investigated. Both systems exhibited an enhancement in the UV band-edge emission from the ZnO when excited at 325 nm. In contrast, the broad bend defect emission of the samples did not have a significant change compare to bare ZnO substrates. The observed results suggested that the ZnO and TiO2 NWs decorated with plasmonic nanoparticles can boost the optical properties of MOs NWs substrates and hence effectively enhance the separation of photoexcited electron-hole pairs and photo-conversion applications.

In this work, I studied the hybrid system based on self-assembled guanosine crystal (SAGC) conjugated to wide-bandgap semiconductor gallium nitride (GaN). Guanosine is one of the four bases of DNA and has the lowest oxidation energy, which favors carrier transport. It also has large dipole moment. Guanosine molecules self-assemble to ribbon-like structure in confined space. GaN surface can have positive or negative polarity depending on whether the surface is Ga- or N-terminated. I studied SAGC in confined space between two electrodes. The current-voltage characteristics can be explained very well with the theory of metal-semiconductor-metal (MSM) structure. I-V curves also show strong rectification effect, which can be explained by the intrinsic polarization along the axis of ribbon-like structure of SAGC. GaN substrate property influences the properties of SAGC. So SAGC has semiconductor properties within the confined space up to 458nm. When the gap distance gets up to 484nm, the structure with guanosine shows resistance characteristics. The photocurrent measurements show that the bandgap of SAGC is about 3.3-3.4eV and affected by substrate properties. The MSM structure based on SAGC can be used as photodetector in UV region. Then I show that the periodic structure based on GaN and SAGC can have photonic bandgaps. The bandgap size and the band edges can be tuned by tuning lattice parameters. Light propagation and emission can be tuned by photonic crystals. So the hybrid photonic crystal can be potentially used to detect guanosine molecules. If guanosine molecules are used as functional linker to other biomolecules which usually absorb or emit light in blue to UV region, the hybrid photonic crystal can also be used to tune the coupling of light source to guanosine molecules, then to other biomolecules.

With the population aging worldwide, new solutions for non-invasive health monitoring are required. Radar systems have been proposed as a promising technology for monitoring vital signs in ambient assisted living (AAL) applications. Monitoring vital signs such as breathing rate, heart rate, and pulse rate can provide crucial insights into human well-being and detect a wide range of medical problems. The main focus of mm-wave radar applications is currently geared towards the automotive market; however, several potential application areas within the broad industrial and healthcare domain are also under active investigation. Their major advantage is that, without the need for any cable or electrode, it is possible, at first, to locate the patient inside the room and, then, to measure their respiratory rate and heartbeat. A contactless detection method offers the simple and fast monitoring of vital signs without the disadvantages of current practices. One very promising approach is the use of radar technology. This thesis focuses on finding the safe way of using mm-Wave propagation in a hospital's real-world scenario and finding the safe range of frequency and power dissipation that won’t be harmful to the human body.  Objective: In this thesis, we investigate the optimum range of frequency and power of mm-Wave propagation, which can be considered safe for usage in an environment like hospitals. Also, the range of power with respect to the power density which can be considered safe for implementation in E-health systems.  Methods: Simulation is considered the method to find various range brackets for different parameters like frequencies, distances, bandwidths, and power. The simulation also helps to get a large number of results for a closer approximation. The received signal is observed to get the desired results, and using the available data, the ranges are found for safe usage of the forementioned technologies.  Results: The results obtained are tabulated to show the relation of received signal strength with all the other parameters like frequency, distance, and power. Then using the power and received signal relation, the safe range of power is calculated, which can be used in a closed environment like hospitals.

Wide band-gap semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) have been widely investigated these years for their preferred operation at higher switching frequency, higher blocking voltage, higher temperature, with a compacter volume, in comparison with the traditional silicon (Si) devices. SiC MOSFETs have been utilized in photovoltaic systems, wind turbine converters, electric vehicles, solid-state transformers, more electric ships, and airplanes. GaN based transistors have also been adopted in the DC-to-DC converters in data centers, personal computers, AC-to-DC power factor correction converters for the consumer electronic adaptors, and DC-to-AC photovoltaic micro-inverters. The first part of this dissertation is regarding the lifetime modeling and condition monitoring for the SiC MOSFETs. Since SiC-based devices have different failure modes and mechanisms compared with Si counterparts, a comprehensive review will be conducted to develop accurate lifetime prediction, condition monitoring, and lifetime extension strategies. First, a novel comprehensive online updated system-level lifetime modeling approach will be presented. Second, to monitor the SiC MOSFET ageing, the typical degradation indicators of SiC MOSFET gate oxide will be investigated. Third, to measure the junction temperature, the dynamic temperature-sensitive electrical parameters for the medium-voltage SiC devices will be studied. The other part is the topology investigation of these emerging wide band-gap devices. A generalized topology that would leverage the advantages of the wide band-gap devices will be introduced and analyzed in detail. Following it is a new evaluation index for comparing different topologies with the consideration of the semiconductor die information. The topology and its derivatives will be utilized in the subsequent chapters for three applications. First, a 100 kW switched tank converter (STC) will be designed using SiC MOSFETs for transportation power electronic systems. Second, an updated STC topology integrating with the partial-power voltage regulation will be introduced for electric vehicle applications. Third, two novel single-phase resonant multilevel modular boost inverters will be designed based on the voltage-regulated STC. These topologies will be validated through designed prototypes. As a result, the high power density and high efficiency will be realized by combining the well-suited topologies and the advantages of the WBG devices.

The design of a dc generation system is posed as a multi-objective optimization problem which simultaneously designs the generator and the power converter. The proposed design methodology captures the interaction between various system component models and utilizes the system steady state analysis, stability analysis, and disturbance rejection analysis. System mass and power loss are considered as the optimization metrics and minimized. The methodology is demonstrated through the design of a notional dc generation system which contains a Permanent Magnet Synchronous Machine (PMSM), passive rectifier, and a dc-dc converter. To this end, a high fidelity PMSM model, passive rectifier model, semiconductor model and passive component model are developed. The output of optimization is a set of designs forming a Pareto-optimal front. Based on the requirements and the application, a design can be chosen from this set of designs. The methodology is applied to SiC based dc generation system and Si based dc generation system to quantify the advantage of Wide Bandgap (WBG) devices. A prototype SiC based dc generation system is constructed and tested at steady state. Finally a thermal equivalent circuit (TEC) based PMSM thermal model is included in the design paradigm to quantify the impact of the PMSM’s thermal performance to the system design.

<p>The first flexible chip-less RFID temperature sensor system for food monitoring to have a  resolution of 0.2  <strong>°</strong>C for temperature measurements between 79  <strong>°</strong>C and -22.8  <strong>°</strong>C is introduced. This  system has a significant improvement in temperature range compared to current flexible RFID  sensors and can provide high accuracy measurements for real time food monitoring at the system  level. Flexible sensors provide low-cost, better flexibility, and longer service life; hence, flexible  sensor systems can provide a new future for food monitoring in commercial applications. The  proposed system presents a new feature and enables a food monitoring system that utilizes a  flexible sensor system. The system introduced in this paper enables a wireless measurement system  providing 100 dB dynamic range with 160 Msps and 16-bit resolution for precise temperature  measurements that are critical for food quality within 100  <strong>°</strong>C temperature range. The full sensing  system is designed, tested and measurements results are confirmed to be within expected accuracy </p>