Traditional implementations of optical receivers are designed to operate with external photodetectors or require integration in a hybrid technology. By integrating a CMOS photodetector monolithically with an optical receiver, it can lead to the advantage of speed performance and cost. This dissertation describes the implementation of a photodetector in CMOS technology and the design of an optical receiver front-end and a clock and data recovery system. The CMOS detector converts the light input into an electrical signal, which is then amplified by the receiver front-end. The recovery system subsequently processes the amplified signal to extract the clock signal and retime the data. An inductive peaking methodology has been used extensively in the front-end. It allows the accomplishment of a necessary gain to compensate for an underperformed responsivity from the photodetector. The recovery circuits based on a nonlinear circuit technique were designed to detect the timing information contained in the data input. The clock and data recovery system consists of two units viz. a frequency-locked loop and a phase-locked loop. The frequency-locked loop adjusts the oscillator’s frequency to the vicinity of data rate before phase locking takes place. The phase-locked loop detects the relative locations between the data transition and the clock edge. It then synchronises the input data to the clock signal generated by the oscillator. A system level simulation was performed and it was found to function correctly and to comply with the gigabit fibre channel specification. / Dissertation (MEng (Micro-Electronics))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

Made available in DSpace on 2014-12-17T14:55:58Z (GMT). No. of bitstreams: 1 TullioEMR_DISSERT.pdf: 2349636 bytes, checksum: 1b35ab0d9433bcc6b9750162da2fd889 (MD5) Previous issue date: 2011-03-25 / Spacecraft move with high speeds and suffer abrupt changes in acceleration. So, an onboard GPS receiver could calculate navigation solutions if the Doppler effect is taken into consideration during the satellite signals acquisition and tracking. Thus, for the receiver subject to such dynamic cope these shifts in the frequency signal, resulting from this effect, it is imperative to adjust its acquisition bandwidth and increase its tracking loop to a higher order. This paper presents the changes in the GPS Orion s software, an open architecture receiver produced by GEC Plessey Semiconductors, nowadays Zarlink, in order to make it able to generate navigation fix for vehicle under high dynamics, especially Low Earth Orbit satellites. GPS Architect development system, sold by the same company, supported the modifications. Furthermore, it presents GPS Monitor Aerospace s characteristics, a computational tool developed for monitoring navigation fix calculated by the GPS receiver, through graphics. Although it was not possible to simulate the software modifications implemented in the receiver in high dynamics, it was observed that the receiver worked in stationary tests, verified also in the new interface. This work also presents the results of GPS Receiver for Aerospace Applications experiment, achieved with the receiver s participation in a suborbital mission, Operation Maracati 2, in December 2010, using a digital second order carrier tracking loop. Despite an incident moments before the launch have hindered the effective navigation of the receiver, it was observed that the experiment worked properly, acquiring new satellites and tracking them during the VSB-30 rocket flight. / Ve?culos espaciais se movem com velocidades elevadas e sofrem mudan?as bruscas de acelera??o. Ent?o, para que um receptor de GPS possa calcular solu??es de navega??o estando a bordo de tais ve?culos, o efeito Doppler deve ser levado em considera??o durante os processos de aquisi??o e rastreio de sinais de sat?lites. Assim, para que o receptor submetido ? alta din?mica comporte os deslocamentos de frequ?ncia no sinal recebido, decorrentes desse efeito, ? necess?rio ajustar sua largura de banda de varredura de frequ?ncias e aumentar a ordem de sua malha de rastreio. Este trabalho apresenta as modifica??es no software no GPS Orion, um receptor de arquitetura aberta da GEC Plessey Semiconductors, hoje Zarlink, a fim de torn?-lo apto a gerar solu??es de navega??o em ve?culos submetidos ? alta din?mica, especialmente sat?lites de ?rbita baixa. A plataforma de desenvolvimento GPS Architect, comercializada pela mesma empresa, foi utilizada para dar suporte ?s modifica??es. Al?m disso, s?o apresentadas as caracter?sticas do Monitor GPS Aeroespacial, uma ferramenta computacional desenvolvida para monitorar as solu??es de navega??o calculadas pelo receptor de GPS atrav?s de gr?ficos. Apesar de n?o ter sido poss?vel fazer simula??es em alta din?mica com as modifica??es de software implementadas no receptor, verificou-se seu funcionamento satisfat?rio, em regime estacion?rio, fazendo uso, inclusive, da nova interface gr?fica. A disserta??o apresenta ainda os resultados do experimento Receptor de GPS para Aplica??es Aeroespaciais, obtidos com a participa??o do receptor numa miss?o suborbital, a Opera??o Maracati 2, em dezembro de 2010, utilizando uma malha de rastreio de portadora digital de segunda ordem. Apesar de um incidente ocorrido momentos antes do lan?amento ter prejudicado a navega??o efetiva do receptor, foi observado que o experimento funcionou adequadamente, rastreando e adquirindo novos sat?lites durante o voo do foguete VSB-30.

The unconventional improvements in the power electronics field have been the primary reason for massive deployment of renewable energy sources in the electrical power grid over the past several decades. This needed trend, together with the increasing penetration of micro-, and nano- grids, is bringing significant improvements in system controllability, performance, and energy availability, but is fundamentally changing the nature of electronically-interfaced sources and loads, altering their conventionally mild aggregate dynamics, and inflicting low- and high- frequency dynamic interactions that never before existed at this magnitude. This problem is not restricted only to the grid; modern electronic power distribution systems built for airplanes, ships, electric vehicles, data-centers, and homes, comprise dozens, even hundreds of power electronics converters, produced by different manufacturers, who provide very limited details on converters' dynamic behavior - distinctiveness that has the highest impact on how two converters, or converter and a system interact. Consequently, substantial dispersion of power electronics into the future grid will significantly depend on engineers' capability to understand how to model and dynamically control power flow and subsystem interactions. It is therefore essential to continue developing innovative methods that allow easier system-level modeling, continuous monitoring of dynamic interactions, and advanced control concepts of power electronics converters and systems. The dissertation will start with a "black box" approach to modeling of three-phase power electronics converters, introducing a method to remove source and load dynamics from in-situ measured terminated frequency responses. It will be then shown how converter, itself, can perform an online stability assessment knowing its own unterminated dynamics, and being able to measure all terminal immittances. The dissertation will further advance into an approach to control power electronics converters based on the electro-mechanical duality with synchronous machines, and end with selected examples of system-level operation, where small-signal instability in multi-source power systems can be mitigated using this concept. / Ph. D. / The modern technological advancements and ever-increasing needs for a sustainable future silently demand a serious revision of the conventional practice in electricity production, distribution, and utilization. These technologies are already challenging the limits of the biggest and most complex system ever built by humankind - the electrical grid. One practical solution to this problem is much higher dispersion of electronic power conversion systems capable of decoupling dynamics between system sources, distribution, and loads, while improving system controllability, reliability, and efficiency. Such a trend is already happening, and there has been an increased immersion of power electronics converters in electric cars, ships, airplanes, and the grid, in an effort to replace their traditional thermal, mechanical, hydraulic, and pneumatic systems. The goals have been to reduce the size, weight, and operational costs while increasing efficiency and reliability. In all these applications, a majority of energy sources and loads are interfaced to the power system through power electronics converters ranging in power from few watts to hundreds of megawatts. However, massive dispersion of power electronics into the future grid will significantly depend on engineers’ capability to understand how to model and dynamically control power flow and subsystem interactions. It is important to continue researching innovative methods that allow easier system-level modeling, continuous monitoring of interactions, and advanced control concepts of power electronics converters and systems. This dissertation hence addresses modeling of power electronics converters using their behavioral models, and shows how these models can assist the stability assessment of the system converters operate in. Additionally, dissertation presents an alternative way to control power electronics converters to behave as synchronous machines, and how this concept can be used to mitigate some stability problems.