Demodulação de sinais interferométricos de saída de sensor eletro-óptico de tensões elevadas utilizando processador digital de sinais
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Data
2013-10-31
Autores
Pereira, Fernando da Cruz [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O grupo de estudos do Laboratório de Optoeletrônica (LOE) da FEIS-UNESP trabalha há vários anos na área de interferometria óptica. A expressão geral da transmissão (razão entre o retardo de fase e a tensão aplicada) de um modulador eletro-óptico de intensidades é idêntica à expressão do sinal fotodetectado na saída de um interferômetro de dois feixes. Em 2012, um novo método de detecção interferométrica de fase óptica foi desenvolvido no LOE, sendo denominado de método de segmentação do sinal amostrado (SSA). Este método é imune ao fenômeno de desvanecimento, é capaz de mensurar o valor da diferença de fase quase-estática entre os braços do interferômetro, consegue medir o tempo de atraso entre o estímulo e a resposta, é pouco sensível ao ruído eletrônico, apresenta excelente resolução, tem ampla faixa dinâmica, permite caracterizar dispositivos não-lineares e pode operar com uma grande variedade de sinais periódicos não-senoidais. Beneficiando-se dessas informações, promoveu-se uma adaptação do método SSA para fins de se implementar um sensor óptico de tensão (SOT) elevada, a base do efeito eletro-óptico linear em cristais de niobato de lítio. O trabalho desenvolvido nesta dissertação se insere nesta linha de pesquisa, porém, ao contrário de trabalhos pregressos realizados no LOE, onde o sinal fotodetectado era amostrado por um osciloscópio digital e processado em microcomputador, agora, empregam-se processadores digitais de sinais (DSPs) tanto para amostrar quanto processar o sinal. Operando-se com a placa eZdspF28335, de ponto-flutuante, foram executadas medições da forma de onda de sinais de alta tensão, em 60 Hz e com elevado conteúdo de harmônicas superiores. Desta forma, gráficos de linearidade (relação entre o retardo induzido versus tensão elétrica aplicada)...
The Optoelectronic Laboratory (OEL) research group has been working for many years in the optical interferometry field. The general expression for the transmission (phase shift and drive voltage ratio) of an electro optic amplitude modulator is identical to the photo-detected signal at the output of a two-beam interferometer. In 2012, a new interferometry method for optical phase detection was developed at OEL, named Sampled Piece-Wise Signal (SPWS) method. This method, which is immune to fading, is used to measure the value of the quasi-static optical phase difference between the arms of the interferometer. The method has small influence from to electronic noise, provides excellent resolution, has a wide dynamic range, and allows the characterization of non-linear devices. Furthermore, the SPWS method is used to measure the time delay between stimulus and response and may operate with a wide variety of non-sinusoidal periodic signals. In this work the SPWS method is adjusted aiming the high voltage measurement by using an optical voltage sensor (OVT) based on the linear electro-optic effect in lithium niobate crystals. Unlike previous studies realized at OEL, where the photo-detected signal was acquired by a digital oscilloscope and processed with a microcomputer, a digital signal processor (DSPs) is employed for both signal acquisition and processing. Measurements of high voltage signal waveforms, at 60 Hz and with higher harmonic content, were performed using the eZdspF28335 card, with floating-point operation. Thus, OVT linearity (induced phase shift versus drive voltage) and frequency response curves were obtained. The spectrum of the high voltage signal was calculated, and hence, parameters such as THD (Total Harmonic Distortion) and IHD (Individual Harmonic Distortion) could be determined. Two different OVT configurations were tested... (Complete abstract click electronic access below)
The Optoelectronic Laboratory (OEL) research group has been working for many years in the optical interferometry field. The general expression for the transmission (phase shift and drive voltage ratio) of an electro optic amplitude modulator is identical to the photo-detected signal at the output of a two-beam interferometer. In 2012, a new interferometry method for optical phase detection was developed at OEL, named Sampled Piece-Wise Signal (SPWS) method. This method, which is immune to fading, is used to measure the value of the quasi-static optical phase difference between the arms of the interferometer. The method has small influence from to electronic noise, provides excellent resolution, has a wide dynamic range, and allows the characterization of non-linear devices. Furthermore, the SPWS method is used to measure the time delay between stimulus and response and may operate with a wide variety of non-sinusoidal periodic signals. In this work the SPWS method is adjusted aiming the high voltage measurement by using an optical voltage sensor (OVT) based on the linear electro-optic effect in lithium niobate crystals. Unlike previous studies realized at OEL, where the photo-detected signal was acquired by a digital oscilloscope and processed with a microcomputer, a digital signal processor (DSPs) is employed for both signal acquisition and processing. Measurements of high voltage signal waveforms, at 60 Hz and with higher harmonic content, were performed using the eZdspF28335 card, with floating-point operation. Thus, OVT linearity (induced phase shift versus drive voltage) and frequency response curves were obtained. The spectrum of the high voltage signal was calculated, and hence, parameters such as THD (Total Harmonic Distortion) and IHD (Individual Harmonic Distortion) could be determined. Two different OVT configurations were tested... (Complete abstract click electronic access below)
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Palavras-chave
Eletronica - Instrumentos, Processamento de sinais - Tecnicas digitais, Interferometria, Optoeletronica, Eletrootica, Signal processing Digital techniques
Como citar
PEREIRA, Fernando da Cruz. Demodulação de sinais interferométricos de saída de sensor eletro-óptico de tensões elevadas utilizando processador digital de sinais. 2013. 125 f. Dissertação (mestrado) - Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Engenharia de Ilha Solteira, 2013.