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Thesis deals with the analysis of the sliding contact in the ring mill. It focuses on the assessment of the effect of the current load on the sliding contact, the assessment of the signal transmission quality from the static to the rotara part of the ring contact slide contact.

Submitted by Rosana Moreira (rosanapsm@outlook.com) on 2018-07-18T20:35:14Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_ModellingMitigationAlien.pdf: 3291316 bytes, checksum: ebf7063697382b3f3868d4b8e6d3faa0 (MD5) / Approved for entry into archive by Luciclea Silva (luci@ufpa.br) on 2018-07-19T12:20:20Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_ModellingMitigationAlien.pdf: 3291316 bytes, checksum: ebf7063697382b3f3868d4b8e6d3faa0 (MD5) / Made available in DSpace on 2018-07-19T12:20:20Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_ModellingMitigationAlien.pdf: 3291316 bytes, checksum: ebf7063697382b3f3868d4b8e6d3faa0 (MD5) Previous issue date: 2017-12-11 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / G.fast é o padrão mais recente do ITU-T para transmissões DSL, o qual e destinado para topologias do cobre de curtas distâncias e adota uma largura de banda de 106 MHz, que pode ser extendida at é 212 MHz. Em muitas situações os sistemas G.fast serão compostos ou coexistirão com linhas não-coordenadas (o linhas alien), as quais são fonte de forte crosstalk, pois estas linhas não fazem parte do grupo vetorizado. Este documento apresenta uma formula ção que explica o desempenho de m étodos de mitiga ção de alien crosstalk de acordo com o n úmero de linhas alien no ambiente, o mecanismo que defi ne a correla ção desta interferência e um m étodo de mitiga ção de alien crosstalk para transmissões DSL na dire ção de downstream afetadas por m últiplos interferentes, chamado AMMIS. Os resultados das simula c~oes mostram que os m étodos de mitiga c~ao de alien crosstalk encontrados na literatura podem de fato melhorar o desempenho de sistemas G.fast, mas apenas em condi ções específi cas. N os contrastamos estas situa c~oes e apresentamos diretrizes acerca da viabilidade destas t écnicas de mitigação em cen ários com n úmeros distintos de linhas alien. Adicionalmente, o AMMIS apresenta resultados promissores em rela c~ao a taxa de dados quando comparado com os m etodos encontrados na literatura em cen arios com grande quantidade de interferentes, com a vantagem adicional de ainda possibilitar economia de energia. Como suporte para as simula ções, tamb ém apresentamos um conjunto de medi ções de alien crosstalk. / G.fast is the most recent ITU-T standard for DSL transmission, which targets copper topologies with short distances and adopts a bandwidth of 106 MHz extensible to 212 MHz. In several situations, G.fast systems will be composed by or coexist with uncoordinated (or alien) lines, which are sources of strong crosstalk, because these lines are not part of the vectored group. This document presents a formulation to explain the performance of the alien crosstalk mitigation methods according to the number of alien lines in a certain environment, the mechanism that de nes the interference correlation of it and an alien crosstalk mitigation method for downstream DSL transmission impaired by multiple interferers called AMMIS. Simulation results show that alien crosstalk mitigation methods found in the literature can indeed improve the performance of G.fast systems, but only under speci c conditions. We have contrasted these situations and we provide guidelines about the feasibility of the crosstalk mitigation techniques in scenarios with distinct number of alien lines. Additionally, the AMMIS shows promising results in relation to the bit rate when compared with literature methods in scenarios with a large number of interferers, with the additional advantage of allows power savings. As support for the simulations, we also present a set of alien crosstalk measurements.

With 400 Gbps Ethernet being developed at the time of writing this thesis, all-optical networks are a solution to the increased bandwidth requirements of data communication allowing architectures to become increasingly integrated. High density integration of optical components leads to potential ‘Optical/Photonic’ electromagnetic compatibility (EMC) and signal integrity (SI) issues due to the close proximity of optical components and waveguides. Optical EMC issues are due to backscatter, crosstalk, stray light, and substrate modes. This thesis has focused on the crosstalk in Optical Add/Drop Multiplexers (OADMs) as an EMC problem. The main research question is: “How can signal integrity be improved and crosstalk effects mitigated in small-sized OADMs in order to enhance the optical EMC in all-optical networks and contribute to the increase in integration scalability?” To answer this question, increasing the crosstalk suppression bandwidth rather than maximizing the crosstalk suppression ratio is proposed in ring resonator based OADMs. Ring resonators have a small ‘real estate’ requirement and are, therefore, potentially useful for large scale integrated optical systems. A number of approaches such as over-coupled rings, vertically-coupled rings and rings with random and periodic roughness are adopted to effectively reduce the crosstalk between 10 Gbps modulated channels in OADMs. An electromagnetic simulation-driven optimization technique is proposed and used to optimize filter performance of vertically coupled single ring OADMs. A novel approach to analyse and exploit semi-periodic sidewall roughness in silicon waveguides is proposed. Grating-assisted ring resonator design is presented and optimized to increase the crosstalk suppression bandwidth.

How can we evaluate and design integrated photonic circuit performance systematically? Can active photonic circuits be controlled for optimized performance? This work uses control theory to analyze, design, and optimize photonic integrated circuits based on versatile semiconductor optical amplifiers (SOAs). Control theory provides a mathematically robust set of tools for system analysis, design, and control. Although control theory is a rich and well-developed field, its application to the analysis and design of photonic circuits is not widespread. Following control theoretic methods already used for fibreline systems we derive three interrelated state-space models: a core photonic model, a photonic model with gain compression, and a equivalent circuit optoelectronic model. We validate each model and calibrate the gain compression model by pump/probe experiments. We then linearize the state-space models to design and analyze SOA controllers. We apply each linearized model to proof-of-concept SOA control applications such as suppressing interchannel crosstalk and regulating output power. We demonstrate the power of linearized state-space models in controller design and stability analysis. To illustrate the importance of using the complete equivalent circuit model in controller design, we demonstrate an intuitive bias-current controller that fails due to the dynamics of the intervening parasitic circuitry of the SOA. We use the linearized state-space models to map a relationship between feedback delay and controller strength for stable operation, and demonstrate that SOAs pose unusual control difficulties due to their ultrafast dynamics. Finally, we leverage the linearized models to design a novel and successful hybrid controller that uses one SOA to control another via feedback (for reliability) and feedforward (for speed) control. The feedback controller takes full advantage of the equivalent circuit modelling by sampling the voltage of the controlled SOA and using the error to drive the bias current of the controller SOA. Filtering in the feedback path is specified by transfer function analysis. The feedforward design uses a novel application of the linearized models to set the controller bias points correctly. The modelling and design framework we develop is entirely general and opens the way to the robust optoelectronic control of integrated photonic circuits.

How can we evaluate and design integrated photonic circuit performance systematically? Can active photonic circuits be controlled for optimized performance? This work uses control theory to analyze, design, and optimize photonic integrated circuits based on versatile semiconductor optical amplifiers (SOAs). Control theory provides a mathematically robust set of tools for system analysis, design, and control. Although control theory is a rich and well-developed field, its application to the analysis and design of photonic circuits is not widespread. Following control theoretic methods already used for fibreline systems we derive three interrelated state-space models: a core photonic model, a photonic model with gain compression, and a equivalent circuit optoelectronic model. We validate each model and calibrate the gain compression model by pump/probe experiments. We then linearize the state-space models to design and analyze SOA controllers. We apply each linearized model to proof-of-concept SOA control applications such as suppressing interchannel crosstalk and regulating output power. We demonstrate the power of linearized state-space models in controller design and stability analysis. To illustrate the importance of using the complete equivalent circuit model in controller design, we demonstrate an intuitive bias-current controller that fails due to the dynamics of the intervening parasitic circuitry of the SOA. We use the linearized state-space models to map a relationship between feedback delay and controller strength for stable operation, and demonstrate that SOAs pose unusual control difficulties due to their ultrafast dynamics. Finally, we leverage the linearized models to design a novel and successful hybrid controller that uses one SOA to control another via feedback (for reliability) and feedforward (for speed) control. The feedback controller takes full advantage of the equivalent circuit modelling by sampling the voltage of the controlled SOA and using the error to drive the bias current of the controller SOA. Filtering in the feedback path is specified by transfer function analysis. The feedforward design uses a novel application of the linearized models to set the controller bias points correctly. The modelling and design framework we develop is entirely general and opens the way to the robust optoelectronic control of integrated photonic circuits.

No description available.

No description available.

The dissertation investigates the issues of analyzing a digital Sigma-Delta digital-to-analog converter (DAC) for audio power amplifiers. The main objects of research include a digital Sigma-Delta audio power DAC, improvement of its structure and an experimental research. The primary purpose of the dissertation is to suggest methods for improvement the structure of digital Sigma-Delta audio power DAC interpolator and the converter analysis. / Disertacijoje nagrinėjami Sigma-Delta skaitmeniniai-analoginiai (skaičiaus-analogo, SA) keitikliai garso galios stiprintuvams. Pagrindinis tyrimų objektas – skaitmeninis Sigma-Delta garso galios SA keitiklis, jo sandaros tobulinamas bei eksperimentinis tyrimas. Disertacijos tikslas – pasiūlyti skaitmeninio Sigma-Delta garso galios SA keitiklio interpoliatoriaus struktūros tobulinimo bei keitiklio tyrimo metodus.

In xDSL technology, high-speed data are transferred between the central office and the customers, or between two or more central offices using unshielded telephone lines. A major impairment that hinders the increase in data-rate through the twisted-pair line is nearend crosstalk (NEXT) between the adjacent twisted pairs. DSL systems with overlapping transmit and receive spectra are susceptible to NEXT which significantly increases the interference noise in the received signal and also reduces the reliability and availablity of the system. One way to cancel the NEXT in the received signal is to deploy adaptive filters. However, if adaptive filters are deployed to cancel every possible NEXT signal from the other twisted pairs, the computational complexity increases in proportion to N2 where N is the number of twisted pairs in the bundle and, therefore, it becomes prohibitive even for small values of N. In this dissertation, four new methods for NEXT reduction are proposed. The methods aim at reducing computational complexity while maintaining speed and performance. In Chapter 3 an efficient NEXT cancellation system is proposed. The new system first detects the NEXT signals present in the received signal and then assigns adaptive filters to cancel the most significant NEXT signals detected. The detection process uses a fast and efficient algorithm that estimates the crosscorrelation between the transmitted and received signal. By subtracting the adaptive filter estimates of the NEXT signals that have been detected and assigned adaptive filters for cancellation, the magnitude of smaller NEXT signals can be estimated more accurately during the NEXT detection stage. The new system offers an overall computational complexity of order N. This represents a large reduction in the computational effort relative to that in previous NEXT cancellation system which offer computational complexities of order N2. In Chapter 4, the NEXT cancellation system proposed in Chapter 3 is implemented using frequency-domain least-mean-square (FDLMS) adaptive filters to cancel the NEXT signals. Several schemes for assigning the adaptive filter step sizes are explored. It has been found that by making the step sizes proportional to the magnitude of the NEXT signals during the initial phases of adaptation and then making them all equal during the later phases, the convergence rate can be significantly improved. And by returning after convergence to step sizes that are proportional to the magnitudes of the NEXT signals, a much better tracking performance is achieved. In Chapter 5, a new technique that reduces the computational complexity in adaptive filters for NEXT cancellation is proposed. In this technique, the filter length of each adaptive filter is adjusted according to the strength of the NEXT signal. Since the NEXT signals from the other twisted pairs are typically of different magnitudes, using such a technique leads to a significant reduction in the total number of filter taps when compared with fixedlength adaptive filters. The NEXT cancellation is started by using adaptive filters with minimum filter lengths. As the adaptation progresses, the filter length of each adaptive filter is adjusted according to the magnitude of the NEXT signal. Upon convergence, another algorithm is deployed which readjusts the filter lengths of those adaptive filters that are too long or too short. Chapter 6 deals with another new method to mitigate NEXT based on a wavelet denoising technique. In xDSL systems, the received signal typically has greater power in the lower end of the frequency spectrum whereas the NEXT signal has greater power in the higher end. The wavelet technique takes advantage of the difference between the power spectrum of the received signal and that of the NEXT to mitigate the crosstalk noise. In addition, the method has a low computational complexity which makes it fast, efficient, and well suited for high data-rate applications.