Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 108-111). Also available in electronic format on the Internet.

Thesis (Ph.D.(Electronic engineering))--University of Pretoria, 2008. / Summary in English. Includes bibliographical references.

Orientador: Aldario Chrestani Bordonalli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-12T14:34:08Z (GMT). No. of bitstreams: 1 Benitez_JefersonLuiz_M.pdf: 1285150 bytes, checksum: f415e987beef32dcbeef939567c5c29c (MD5) Previous issue date: 2008 / Resumo: As propriedades do ganho cruzado em amplificadores ópticos semicondutores visando a geração de sinais de RF é investigada experimentalmente neste trabalho. Observou-se que a utilização de amplificadores ópticos altamente saturados e realimentados opticamente pode ter desempenho similar ao caso de vários amplificadores em cascata nas aplicações de geração de sinais de RF, oferecendo um ganho acima de 10 dB para duas portadoras ópticas moduladas e separadas de 8 nm. A saturação altera o mecanismo de ganho do amplificador, produzindo um efeito de mistura entre as componentes de modulação dos sinais ópticos. Para portadoras ópticas moduladas em 250 MHz e 400 MHz, produziu-se, após a fotodetecção, componentes eletrônicas com freqüências de batimento de 150 e 650 MHz. / Abstract: The gain-crossed properties of semiconductor optical amplifiers are experimentally investigated here. It was observed that optically feed-backed saturated amplifiers could achieve similar performance as that of cascaded amplifiers, offering up to 10 dB gain to two 8-nm-appart modulated optical carriers. Due to saturation the amplifier gain mechanism is altered leading to a mixing effect that causes the frequency components of the optical signals to be exchanged. For optical carriers modulated at 250 MHz and 400 MHz, this mixing effect produced, after photodetection, up and down-converted electronic components at 650 and 150 MHz, respectively. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Ph. D.

This dissertation research had three primary objectives. The first was to develop and evaluate a metric of image quality that incorporates a model of suprathreshold contrast and is based upon the perceived magnitude of suprathreshold contrast. The second objective was to determine the effects that common display characteristics, such as MTF shape, noise, and field of view, have on a display observer's ability to perceive egocentric motion from a display. The third and final objective was to provide a discussion of the use of image quality metrics for the evaluation of displays that are designed to facilitate motion perception. To meet these objectives, two experiments were conducted. The first experiment investigated the effects of the display Field of View, Dynamic Contrast Range, Noise Level, and Bandwidth on perceived image quality. The second study investigated the effects of these same display parameters as well as the effect of terrain type on observers’ sensitivity to changes in the speed of image motion. Existing visual psychophysical data were used to propose the two additional image quality metrics, the Perceived Contrast Magnitude (PCM) and the Weighted Perceived Contrast Magnitude (WPCM). Each of these metrics provides some additional model parameters to the Modulation Transfer Function Area (MTFA). However, based upon the studies that were conducted in this dissertation, it appears that the Integrated Contrast Sensitivity (ICS) and Square Root Integral (SQRI) provide significantly better estimates of perceived image quality than do MTFA, PCM, or WPCM. Results indicate that the display parameters of Bandwidth, Field of View, and Noise Level, plus several interactions significantly influenced the observers’ sensitivity to changes in the speed of images. One interaction indicated that observers were more sensitive to changes in the speed of images when the scene contained a lot of contextual information or when the scene was viewed through a display with reasonably high bandwidth and low noise level. However, when the bandwidth of the system was decreased, the noise level was increased, and the contextual information in the image was reduced, the observer's sensitivity to changes in motion was degraded when viewing the image through a small field of view display (20 deg) but it was not degraded when viewing the image through a larger field of view display (47 deg). Based upon the evidence collected in this dissertation, it appears that displays designed to support motion perception should have a relatively large field of view with partitions to facilitate relative motion perception. The factors of Dynamic Contrast Range and Field of View were shown to have different effects on the perception of image quality than they have on the perception of changes in the speed of an image. Therefore, the use of image quality metrics for the evaluation and design of displays that must support the veridical perception of motion should be questioned. Instead, it appears that a task specific evaluation technique should be developed for the evaluation of these displays. / Ph. D.

Present analog optical fiber multi-channel video transmission systems are very sensitive to laser nonlinearities and are consequently limited in the optical modulation depth (OMD) that may be used. This, in turn limits the power budget achievable, signal-to-noise ratio, and the channel capacity. In this dissertation a new analog transmission technique for multi-channel TV transmission on fiber USIng frequency modulation/pulse amplitude modulation/time division multiplexing (FM/TDM) is described and compared with present digital and analog systems. Parameters for the proposed system are selected and the relationship between the performance and parameter values is discussed. Analysis and simulations indicate that the proposed system has a very low sensitivity to nonlinearities and is similar to that of digital systems, and much better than current Frequency Modulated/Frequency Division Multiplexed (FM/FDM) systems. This permits the use of higher OMD (as high as in digital systems), which results in achieving a high signal-to-noise ratio and a large power budget. Analysis of the number of channels as a function of adjacent channel intersymbol interference indicates that the proposed system has a better spectral efficiency than present analog systems. Simulations are also used to predict the performance of the proposed system with laser diodes poorer than the ones presently used for multi-channel analog systems. Considerably poorer lasers may be used while achieving acceptable transmission quality. Finally, carrier-to-noise penalty caused by timing errors and jitter effects are analyzed. / Ph. D.

The estimation of the stability of radar emissions is of considerable interest in the evaluation of radar clutter rejection performance and also for the general knowledge of the waveform required for the design of threat simulators. It should be stressed that for the estimation of clutter rejection capability, it is the stability of the entire waveform that is of general importance, although the stability of parameters such as phase, Pulse Repetition Interval (PRI) and amplitude are typically specified because of the ease in instrumenting the measurement. The parametric estimates are indeed the most useful in describing the characteristics of the waveform but not necessarily for evaluating clutter rejection performance. Two broad categories into which radar emissions can be subdivided are coherent and non-coherent RF. A great deal of confusion often surrounds the use of these terms, especially among those who measure radar emissions rather than those who build the radar sets. For the purposes of this paper, coherence will be defined in terms of the square root of the variance of the first pulse-to-pulse phase difference, Ï (Δθ ). For the case where Ï (Δθ) << 1 radian, the signal will be considered coherent. When the phase is uniformly distributed over 2Ï radians, the signal will be considered nonâ coherent. Since it is likely that, for most practical signals, the signal will be well within one of these two categories, ambiguity will be unlikely. If a radar emission is observed to be coherent, it implies that the radar uses this property for Moving Target Indication (MTI) processing. The performance of the MTI will probably, but not necessarily, depend on the pulse-to-pulse phase stability as the most critical parameter for this type of system. Alternatively, if the radar emission is observed to be non-coherent, it implies that if the radar has an MTI processor, it is likely that it is of the stored reference variety. The performance of the MTI will probably, but again not necessarily, depend on the pulse-to-pulse RF stability as the most critical parameter. The common thread between the two types of systems which indicates clutter rejection performance is the repeatability of adjacent pulse waveforms regardless of phase. This is not to imply that phase is not critical; it is important for determining the type of processor. The difference lies in the fact that for the internally coherent system, the phase information of the coherent reference oscillator is not observable as it is for the extremely coherent system. Hence, the only hint that such an emitter has an MTI processor is contained in the repeatability of adjacent pulse waveforms. This paper addresses the general problems of detecting coherence, estimating MTI performance, and estimating the phase stability, frequency stability and PRI stability using sample data derived from a system based on the IBM-PC. Both the analysis and radar waveform generation systems were implemented in software utilizing Microsoft Fortran and Microsoft C compilers. / Master of Science

The methods of modeling and measurement of switching converters are discussed in this thesis. The average model is very simple but is inaccurate when modulation frequencies approach to one-half of the switching frequency. The discrete model can accurately predict the modulation envelope of the output voltage, but it is very complex. The discrete-average model combines both average and discrete modeling techniques so that it possesses the advantages of both techniques. The experimental results show the deficiency of analog modulation technique for loop gain measurement under certain circumstances. The digital modulator, on the other hand, always provides accurate measurement data. The accuracy of the discrete-average model is verified by measurement data using the digital modulator. / Master of Science

Today's information and communication industry is confronted with a serious bottleneck due to the prohibitive energy consumption and limited transmission bandwidth of electrical interconnects. Silicon photonics offers an alternative by transferring data optically and thereby eliminating the restriction of electrical interconnects over distance and bandwidth. Due to the inherent advantage of using the same material as that used for the electronic circuitry, silicon photonics also promises high volume and low cost production plus the possibility of integration with electronics. In this thesis, I introduce an all-silicon optical interconnect architecture that promises very high integration density along with very low energy consumption. The basic building block of this architecture is a vertically coupled photonic crystal cavity-waveguide system. This vertically coupled system acts as a highly wavelength selective filter. By suitably designing the waveguide and the cavity, at resonance wavelength of the cavity, large drop in transmission can be achieved. By locally modulating the material index of the cavity electrically, the resonance wavelength of the cavity can be tuned to achieve modulation in the transmission of the waveguide. The detection scheme also utilizes the same vertically coupled system. By creating crystal defects in silicon in the cavity region, wavelength selective photodetection can be achieved. This unique vertical coupling scheme also allows us to cascade multiple modulators and detectors coupled to a single waveguide, thus offering huge channel scalability and design and fabrication simplicity. During this project, I have implemented this vertical coupling scheme to demonstrate modulation with extremely low operating energy (0.6 fJ/bit). Furthermore, I have demonstrated cascadeability and multichannel operation by using a comb laser as the source that simultaneously drives five channels. For photodetection, I have realized one of the smallest wavelength selective detector with responsivity of 0.108 A/W at 10 V reverse bias with a dark current of 9.4 nA. By cascading such detectors I have also demonstrated a two-channel demultiplexer.

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