This thesis describes the application of commercially available microprocessors and other VLSI devices to high-speed real-time digital correlation in spread spectrum and related communication applications. Spread spectrum communications are a wide-band secure communication system that generate a very broad spectral bandwidth signal that is therefore hard to detect in noise. They are capable of rejecting intentional or unintentional jamming, and are insensitive to the multipath and fading that affects conventional high frequency systems. The bandwidth of spread spectrum systems must be large to obtain a significant performance improvement. This means that the sequence rate must be fast and therefore very fast microprocessors will be required when they are used to perform spread spectrum correlation. Since multiplication cannot be performed efficiently by microprocessors considerable work, since 1974, has been published in the literature which is devoted to minimising the requirement of multiplications in digital correlation and other signal processing algorithms. These fast techniques are investigated and implemented using general-purpose microprocessors. The restricted-bandwidth problem in microprocessor-based digital correlator has been discussed. A new implementation is suggested which uses bit-slice devices to maintain the flexibility of microprocessor-based digital correlation without sacrificing speed. This microprocessor-based system has been found to be efficient in implementing the correlation process at the baseband in the digital domain as well as the post-correlation signal processing- demodulation, detection and tracking, especiaJIy for low rate signals. A charge coupled-device is used to obtain spectral density function. An all-digital technique which is programmable for any binary waveform and can be used for achieving initial acquisition and maintaining synchronisation in spread spectrum communications is described. Many of the practical implementation problems are discussed. The receiver performance, which is measured in terms of the acquisition time and the bit-error rate, is also presented and results are obtained which are close to those predicted in the system simulations.

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No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 210-211). Available also in a digital version from Dissertation Abstracts.

This thesis describes an investigation into the use of electrical impedance tomography used in conjunction with a flexible conductive sensor for the measurement of distributed pressure. The main application areas are for the constant monitoring of the pressure distribution between a patient and their support surface i.e. beds and wheel chairs, in order to reduce the formation of pressure sores and tactile sensing for robotics. A number of systems have been developed for the monitoring of patients but non-have proved suitable for constant monitoring and these are reviewed. A review of the tactile sensor techniques used in robotic grippers is presented and when the area to be monitored is relatively small (1-2 cm2) the techniques already under development can provide the resolution required. However no technique exists to measure distributed pressure over a large area. A review of both the hardware and reconstruction algorithms used in electrical impedance tomography is presented and the design of the hardware and software developed for the investigation into the sensor design is detailed. As the sensor is such that electrodes are not limited to the periphery both an experimental and computer simulated comparison of three different electrode configurations is described. The three-electrode arrangements investigated are with the electrodes placed at the periphery of both a circular and square boundary, and with electrodes evenly distributed across a square area. The results from the comparisons show that the new distributed electrode arrangement performs significantly better than when the electrodes are confined to the periphery. It also shows that the geometry of the boundary when using peripheral electrodes can also effect the performance of an EIT system. The initially investigated sensor design was based on a conductive polymer sheet and a number of samples were characterised in term of their V/I characteristics and their creep and resistance change due to applied pressure. Only one of the sample tested had a response worth investigating further but the material could not be obtained for larger area tests. Therefore an alternative sensor design was investigated. This novel sensor consisted of a conductive fluid retained beneath a flexible rubber membrane. From electrical impedance tomography images obtained from the experimental evaluation of the new sensor design it is shown that the system can image the pressure distribution across its surface. In addition, the analysis of the unprocessed data from the new sensor shows the system to have a well-defined response with a wide applied pressure range and the construction of the sensor is such that its response could be tailored to the range of pressure to be measured.

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There is scarcely an engineering company in Britain which has not had to face radical changes in technology and world economic climate during the past decade. These companies have been forced to reorganise both their product policy and personnel and have either foundered or emerged the stronger as a result of these inevitable pressures from sources beyond their control. This thesis tells the story of just such a well-established mechanical engineering company which was forced out of its complacency of fifty years into a new aggressive and extremely competitive market, that of electronic gauging and measurement, and was able to recover from the brink of financial collapse because of its thrust into new technology and the resultant research, design and development of new and different products. For the first time in fifty years British Indicators Ltd was forced to innovate in order to survive.

No description available.

No description available.