Pulse time modulation (PTM) techniques have drawn considerable attention over the years as suitable schemes for transmission of information over optical fibres. PTM schemes are known to utilise the vast optical bandwidth to provide efficient transmission characteristics. Pulse code modulation is one such modulation scheme that has been used widely in various communication systems. In this thesis digital pulse interval modulation (DPIM), a form of PTM, is proposed as a suitable modulation scheme for optical communication systems. In this scheme the information is represented by means of varying the anisochronous frame interval between two successive pulses. Each pulse fulfils the dual role of representing the frame boundaries and initiation of the next sampling event within the modulator or sample reconstruction in the demodulator. In this study DPIM frame structure is proposed and sampling criteria, information capacity, bandwidth requirements are discussed in depth. The spectral behaviour of the scheme is investigated and a mathematical model is developed to represent the spectra. The model was numerically evaluated and verified with the practical measurements to prove its validity. Spectral predictions were made for random as well as periodic information signals showing the existence of the distinct slot frequency component, which is used for slot synchronisation. Frame synchronisation is not required as DPIM has self synchronised frame structure. For random signals, slot component is found to be about 15 dB and for periodic single tone sinusoidal signal this was at about 5 dB. Dependency of this component on the various system parameters such as bit resolution, pulse width, pulse shape are discussed. A detailed account of the receiver performance is given. Receiver analysis was carried out for narrow band as well as for wide band channels. Possible error sources are presented and the system performance degradation with these error sources is discussed and a comparison is made with isochronous DPPM and PCM. For performance evaluation of analogue systems, signal-to-noise ratio was mathematically modelled and compared with PCM. This analysis showed that DPIM SNRs shows three important regions as compared to PCM. That is when the SNR is inferior, superior and identical to PCM performance. Threshold levels corresponding to the above regions vary depending on the system bit resolution. A prototype DPIM system was designed and implemented to transmit low speed analogue signal (≈15 kHz) at bit resolutions of 4, 5 and 6 where the slot frequencies are at 510, 990 and 1950 kHz, respectively. Measurements were carried out in order to verify the predicted performance. This results showed close agreement with the predicted. Receiver sensitivity of the prototype at bit error rate of 10^-9 was found to be about -45.5 dBm at all three cases with transmitted average power of -28.8 dBm allowing high optical power budget. The signal-to-noise ratio threshold level of the system was at -47 dBm. Finally, linearity measurements of the overall system were made at the above bit resolutions and the quantitative and qualitative results are presented.

This thesis is concerned with the construction of a transistorized pulse code modulation decoder, the purpose of which is to decode the digital signal into the continuous analog form. The earlier part of this thesis describes the design and construction of a transistorized decoder using the circulated pulse principle. This turned out to be not too practical. The latter part concerns the design and construction of a PCM decoder using a ferrite-core shift register. This design was successful. The decoder has been tested in conjunction with the coder built by R.A. Hafer. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Orientador: Evandro Conforti / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T01:55:52Z (GMT). No. of bitstreams: 1 Castelli_ClaudioSelmi_M.pdf: 2856453 bytes, checksum: 1efb001a79f5f2d885e231abadd78d1f (MD5) Previous issue date: 2007 / Resumo: Uma nova técnica de geração de sinais pulsados de microondas é desenvolvida. Baseia-se na composição de dois sinais arbitrários, um trem de pulsos ultra-rápidos e uma portadora de microondas, originados a partir de diferentes fontes e combinados no domínio óptico de forma a preservar ao máximo as características espectrais e temporais dos sinais. São apresentados os conceitos utilizados na técnica e toda a configuração empregada na sua validação experimental. Os resultados obtidos são discutidos e comparados com os sinais pulsados de microondas gerados a partir de um moderno gerador comercial. Os principais componentes utilizados são também caracterizados e propostas de melhorias são apresentadas. A forma de onda obtida a partir da técnica desenvolvida atingiu os resultados esperados / Abstract: A novel technique of pulsed microwave waveform generation has been developed. It is based on the mixture of two arbitrary signals, an ultra-fast pulse train and a microwave carrier, all generated from different sources and combined in the optical domain in order to preserve the spectral and temporal features as much as possible. The technique's concepts and the setup used for the experimental validation have been presented. The obtained results are discussed and compared to the pulsed microwave signals generated by a modern commercial microwave generator. The main components are also characterized and proposals of improvements have been presented. The waveform resulted from this developed technique reached the expected results / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica