A suite of new collision avoidance systems (CAS) is presented for use in heavy vehicles whose structure and size necessarily impede driver visibility is introduced. The main goal of the project is to determine the appropriate use of each of the commercially available technologies and, where possible, produce a low cost variant suitable for use in proximity detection on large mining industry haul trucks. CAS variants produced were subjected to a field demonstration and, linked to the output from the earlier CAS 1 project, (a production high-definition in-cabin video monitor and r/f tagging system). The CAS 2 system used low cost Doppler continuous wave radar antennae coupled to the CAS 1 monitor to indicate the presence of an object moving at any speed above 3 Km/h relative to the antennae. The novelty of the CAS 3 system lies in the design of 3 interconnected, modules. The modules are 8 radar antennae (as used in CAS 2) modules located on the truck, software to interface with the end user (i.e. the drivers of the trucks) and a display unit. Modularisation enables the components to be independently tested, evaluated and replaced when in use. The radar antennae modules and the system as a whole are described together with the empirical tests conducted and results obtained. The tests, drawing on Monte-Carlo simulation techniques, demonstrate both the 'correctness' of the implementations and the effectiveness of the system. The results of the testing of the final prototype unit were highly successful both as a computer simulation level and in practical tests on light vehicles. A number of points, (as a consequence of the field test), are reviewed and their application to future projects discussed.

We present the results of GaInNAs/GaAs quantum dot structures with GaAsN barrier layers grown by solid source molecular beam epitaxy. Extension of the emission wavelength of GaInNAs quantum dots by ~170nm was observed in samples with GaAsN barriers in place of GaAs. However, optimization of the GaAsN barrier layer thickness is necessary to avoid degradation in luminescence intensity and structural property of the GaInNAs dots. Lasers with GaInNAs quantum dots as active layer were fabricated and room-temperature continuous-wave lasing was observed for the first time. Lasing occurs via the ground state at ~1.2μm, with threshold current density of 2.1kA/cm[superscript 2] and maximum output power of 16mW. These results are significantly better than previously reported values for this quantum-dot system. / Singapore-MIT Alliance (SMA)

A 50 MHz Frequency Modulated Continuous Wave (FMCW) radar system, developed at the University of Saskatchewan to provide improved spatial and temporal resolution measurements of auroral E-region plasma processes, introduces ambiguous spectral information, due to spectral ghosting, for scattering events in which multiple radar echoes are detected. This thesis identifies two Linearly Frequency Modulated (LFM) radar waveforms used by the FMCW system as the source of the ghosting. An analysis procedure designed to counteract the spectral ghosting problem is developed but is not an ideal solution, and therefore replacement of the LFM waveforms is recommended.<p> A detailed investigation of alternative radar waveforms using the Ambiguity Function and Ambiguity Diagram techniques is performed. A frequency coded continuous wave radar waveform based on a composite Costas sequence is proposed as a successor to the LFM waveforms. The composite Costas radar waveform will conserve the spatial and temporal resolutions extended by the LFM waveforms and preclude any spectral ghosting. Implementing the proposed radar waveform and avoiding receiver saturation issues with the mono-static FMCW radar system in which both the transmitting and receiving antenna arrays are simultaneously and continuously active and geographically co-located is also discussed.<p> In addition to this, two 50 MHz backscatter events are presented in this thesis to demonstrate the effectiveness of the FMCW system, notwithstanding the spectral ghosting complication. The first event from November 21, 2009 is identified as a Type 1 instability and the second from September 13, 2009 is identified as a Type 2 instability which lasted for ~ 16 minutes. Linear plasma fluid theory is used to provide a brief interpretation of both scattering events.

A 50 MHz Frequency Modulated Continuous Wave (FMCW) radar system, developed at the University of Saskatchewan to provide improved spatial and temporal resolution measurements of auroral E-region plasma processes, introduces ambiguous spectral information, due to spectral ghosting, for scattering events in which multiple radar echoes are detected. This thesis identifies two Linearly Frequency Modulated (LFM) radar waveforms used by the FMCW system as the source of the ghosting. An analysis procedure designed to counteract the spectral ghosting problem is developed but is not an ideal solution, and therefore replacement of the LFM waveforms is recommended.<p> A detailed investigation of alternative radar waveforms using the Ambiguity Function and Ambiguity Diagram techniques is performed. A frequency coded continuous wave radar waveform based on a composite Costas sequence is proposed as a successor to the LFM waveforms. The composite Costas radar waveform will conserve the spatial and temporal resolutions extended by the LFM waveforms and preclude any spectral ghosting. Implementing the proposed radar waveform and avoiding receiver saturation issues with the mono-static FMCW radar system in which both the transmitting and receiving antenna arrays are simultaneously and continuously active and geographically co-located is also discussed.<p> In addition to this, two 50 MHz backscatter events are presented in this thesis to demonstrate the effectiveness of the FMCW system, notwithstanding the spectral ghosting complication. The first event from November 21, 2009 is identified as a Type 1 instability and the second from September 13, 2009 is identified as a Type 2 instability which lasted for ~ 16 minutes. Linear plasma fluid theory is used to provide a brief interpretation of both scattering events.

Rational harmonic mode-locking (RHML) fiber lasers generating picoseconds pulsewidth at high-repetition-rate have emerged as a key component for the high-bit-rate optical time-division multiplexing (OTDM) communication system. In this research, we have discovered higher order RHML semiconductor optical amplifier fiber laser (SOAFL) has the degradation on mode-locking capacity, and an output pulse-train with un-equalized peak amplitudes. Therefore, the main focus of the dissertation is focused on the pulse quality analysis and improvement of RHML-SOAFL via optical pulse injection. First, we observed the degradation on mode-locked mechanism of the dark-optical-comb injection mode-locked semiconductor optical amplifier fiber laser (SOAFL) at RHML order increases to >8. Such a less pronounced RHML mechanism at higher orders is mainly attributed to the weak mode-locking strength at high RHML orders as compared to continuous-wave (CW) lasing mechanism, which has been quantified by reduction of spectral linewidth and pulse-shortening force, and the ratio of DC/pulse amplitude enhancement for discriminating 1st to 20th-order RHML capability. To overcome the un-equalized RHML peak intensity, optical injection induced gain modulation of a SOA are demonstrated to equalize the peak intensity of 5-GHz and 40-GHz RHML-SOAFL by using 1-GHz inverse-optical-pulse and a reshaped 10-GHz gain-switching FPLD pulse injection, respectively. The optical injection mode-locking models are constructed to simulate the compensation of uneven amplitudes between adjacent RHML pulse peaks before and after pulse-amplitude equalization. The optimized RHML pulse exhibits a signal-to-noise suppression ratio of 45-dB, and the clock amplitude jitter below the threshold limitation of 10%. On the other hand, to avoid the mode-locked degradation on RHML, a 2nd-order fractional Talbot effect induced frequency-doubling of 10-GHz optical pulse-train is demonstrated to backward inject a SOAFL for 40-GHz RHML. In comparison with the SOAFL pulse-train repeated at 40-GHz generated by the 4th-order purely RHML process, the optimized 2nd-order fractional Talbot effect in combination with the 2nd-order RHML mechanism significantly enhances the modulation-depth of RHML, thus improving the on/off extinction ratio of the 40-GHz SOAFL pulse-train. Such a new scheme also provides a more stable 40-GHz RHML pulse-train from the SOAFL with its timing jitter reduce. Finally, we established a SHG-FROG to distinguish linear and nonlinear chirp of 10-GHz soliton HML-SOAFL, and further extracted intra-cavity linear dispersion via simulation of Schrodinger equation. After the procedure, the linear chirp almost dominates chirp characteristics for optical pulse injection HML-SOAFL system.

This research was a collaborative effort between the Air Force Research Laboratory (AFRL) and the University of Texas to examine the laser-tissue interaction of thermal lensing induced by continuous-wave, CW, near-infrared, NIR, laser radiation in the eye and its influence on the formation of a retinal lesion from said radiation. CW NIR laser radiation can lead to a thermal lesion induced on the retina given sufficient power and exposure duration as related to three basic parameters; the percent of transmitted energy to, the optical absorption of, and the size of the laser-beam created at the retina. Thermal lensing is a well-known phenomenon arising from the optical absorption, and subsequent temperature rise, along the path of the propagating beam through a medium. Thermal lensing causes the laser-beam profile delivered to the retina to be time dependent. Analysis of a dual-beam, multidimensional, high-frame rate, confocal imaging system in an artificial eye determined the rate of thermal lensing in aqueous media exposed to 1110, 1130, 1150 and 1318-nm wavelengths was related to the power density created along the optical axis and linear absorption coefficient of the medium. An adaptive optics imaging system was used to record the aberrations induced by the thermal lens at the retina in an artificial eye during steady-state. Though the laser-beam profiles changed over the exposure time, the CW NIR retinal damage thresholds between 1110-1319-nm were determined to follow conventional fitting algorithms which neglected thermal lensing. A first-order mathematical model of thermal lensing was developed by conjoining an ABCD beam propagation method, Beer's law of attenuation, and a solution to the heat-equation with respect to radial diffusion. The model predicted that thermal lensing would be strongest for small (< 4-mm) 1/e² laser-beam diameters input at the corneal plane and weakly transmitted wavelengths where less than 5% of the energy is delivered to the retina. The model predicted thermal lensing would cause the retinal damage threshold for wavelengths above 1300-nm to increase with decreasing beam-diameters delivered to the corneal plane, a behavior which was opposite of equivalent conditions simulated without thermal lensing. / text

No description available.

High cost is a current problem with modern radar systems. Software-defined radios (SDRs) offer a possible solution for low-cost customizable radar systems. An SDR is a radio communi- cation system where, instead of the traditional radio components implemented in hardware, many of the components are implemented in software on a computer or embedded system. Although SDRs were originally designed for wireless communication systems, the firmware of an SDR can be configured into a radar system. With new companies entering the market, various types of low- cost SDRs have emerged. This thesis explores the use of a LimeSDR-Mini in a short-range radar through open software tools and custom code. The LimeSDR-Mini is successfully shown to detect targets at a short range. However, due to the instability of the LimeSDR-Mini, the consistent detection of a target is not possible. This thesis shows how the LimeSDR is characterized and how timing synchronization and instability issues are mitigated. The LimeSDR-Mini falls short of operating reliable in a radar system and other SDR boards need to be explored as viable options. Test setups using coaxial cables and test setups using antennas in an outdoor environment show the instability of the LimeSDR-Mini. The transmitter and the receiver are asynchronous. The timing difference varies slightly from run to run, which results in issues that are exacerbated in a short-range radar. The bleed-through signal is the signal leakage from the transmitter to the receiver. The bleed-through signal prevents the detection of targets at a short-range. Feed-through nulling is a signal processing technique used to eliminate the bleed-through signal so that short- range targets can be detected. The instability of the LimeSDR-Mini reduces the effectiveness of feed-through nulling techniques.

This thesis presents a design methodology for continuous wave (CW) synthetic aperture radar (SAR) systems. The focus is on design considerations specific to small, low-power systems suitable for operation on small aircraft and unmanned aerial vehicles (UAVs). Well-known results which have been derived in other works, such as the radar equation, are explained in the context of low-power, CW systems. Additionally, design issues unique to CW SAR are addressed and the results generalized. A method for controlling feedthrough between antennas is developed, and the resulting limitations on swath width are discussed. Methods are developed which allow an engineer to design a CW SAR system to obtain a given swath width, resolution, and data rate, and necessary tradeoffs are discussed. Using the proposed methodology, designs for two specific SAR systems are developed. Example sections outline the design of two small SAR systems called microASAR and microBSAR. These sections present a real-world application of the methodology and offer explanations of the rationale behind many of the design choices. Straightforward methods for testing different aspects of a completed SAR system are developed and presented. These procedures are carried out using microASAR hardware, and the results are used to validate the design methodology.

Neste trabalho foi desenvolvido um estudo sobre a precessão livre de onda contínua (CWFP-continuous wave free precession), uma condição especial da precessão livre no estado estacionário (SSFP), e algumas aplicações. Os resultados experimentais, e de simulações, mostraram que este sinal é atingido após a passagem por dois estágios iniciais. O primeiro é dependente da não homogeneidade do campo magnético, relacionado a razão Tp/T2*. O segundo, o qual é chamado de estado quasi-estacionáio, é dependente ambos os tempos de relaxação do sistema em estudo, T1 e T2. Este segundo estágio é responsável por levar a magnetização do estado de equilíbrio térmico a um estado verdadeiramente estacionário. Tendo como informação a amplitude da magnetização no estado de equilíbrio térmico e no estado verdadeiramente estacionário, e também do decaimento do sinal durante o estado quasi-estacionário, é possível determinar, rápida e simultaneamente, ambos os tempos de relaxação do sistema, fazendo um único experimento. Esse método oferece aplicações interessantes para o estudo de processos dinâmicos, propostas também neste trabalho. Foi possível verificar que o sinal de CWFP pode ser utilizado para acompanhar cinética de reações, e também variações de viscosidade do meio, por exemplo, em reações de polimerização, associadas à mobilidade molecular em função de mudanças estruturais. Um método para avaliar a condutividade térmica de elastômeros foi proposto, com o fornecimento de resultados quantitativos muito próximos daqueles encontrados na literatura, e que utilizam outros métodos. A dependência do sinal de CWFP com a freqüência de offset também permitiu realizar um estudo, com aplicação em RMN de alta resolução, sobre a supressão de sinal de solvente. Os resultados demonstraram que é necessário fazer alguns ajustes na largura de pulsos, juntamente com o ciclo de fases, para minimizar as anomalias de intensidade e de fase dos sinais no espectro transformado. Essa técnica foi aplicada em espectroscopia ‘in vivo’, a qual permite resolver, por exemplo, problemas como a determinação de açúcares em frutas, onde o sinal é bastante próximo do intenso sinal da água. / In this work a study of the continuous wave free precession (CWFP), a special condition of the steady-state free precession (SSFP), and some applications, was developed. The experimental results, together with simulated ones, have shown that the CWFP signal is attained after two previous stages. The first one is dependent on the non-homogeneity of the magnetic field, related to Tp/T2* ratio. The second, which is called quasi-stationary state, is dependent of both relaxation times, T1 and T2. This second stage allows leading the magnetization in the thermal equilibrium to a truly stationary state. The information of the signal amplitude in the thermal equilibrium and in the steady state, and also the signal decaying during the quasistationary state, allows the fast and simultaneous determination of the relaxation times, performed in a single experiment. This method offers interesting applications for studying dynamical processes, also proposed in this work. It was possible to verify that the CWFP signal can be used to monitor kinetics of reactions, which variations of viscosity are involved, for example, in polymerization reactions, always associated to structural changes. A method for evaluating thermal conductivity in elastomers was proposed, with results in accordance to the literature, which uses other methods. The dependence of the CWFP signal with the offset frequency has permitted to study an application to the High-Resolution NMR, about the solvent suppression. The results demonstrated that it is necessary to perform some adjustments in the pulse width, together the phase cycle, to minimize some phase and intensity anomalies of the frequency-domain signal. This technique was applied in ‘in vivo’ spectroscopy, which can solve, for example, problems with the determination of the sugar content in fresh fruits, where the sugar signal is very close to the intense signal of the water.