This work assesses the performance of reflector antennas under adaptive control. In this study, a conventional reflector antenna is given adaptive control by placing additional feeds in the reflector focal plane. The antenna effectively becomes a Multiple Beam Antenna (MBA). This configuration has received far less attention than the Sidelobe Canceller which achieves spatial discrimination by placing low gain elements in the periphery of the reflector. The applications that motivate this work involve rotating radar antennas subject to main beam interference or multiple targets that must be resolved within a 3-db beamwidth. The possibility of the interference being correlated with the wanted signal is also considered. Within the context of these applications the assessment addresses: The basic (main-beam and sidelobe) cancellation performance of this type of antenna. The influence of beam characteristics such as crossover levels, gain, sidelobe levels, etc. in performance. The Control Laws that avoid cancellation of a wanted signal while rejecting interference even if knowledge in signal direction is only approximate. Algorithms to solve adaptively the above Control Laws at speeds consistent with rotating antennas and rapidly changing interference. The use of the beamformer output to generate a reference signal to avoid cancellation of the wanted signal. An algorithm, so far used in the frequency domain, applied in this work to the space domain with the purpose of avoiding cancellation of the wanted signal in the presence of correlated interference such as multipath. The construction of an experimental antenna is also undertaken and it is demonstrated that adaptive nulling is readily achieved in practice.

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This thesis presents an experimental and theoretical investigation of electrical failure in MOS structures, with a particular emphasis on short-pulse and ESD failure. It begins with an extensive survey of MOS technology, its failure mechanisms and protection schemes. A program of experimental research on MOS breakdown is then reported, the results of which are used to develop a model of breakdown across a wide spectrum of time scales. This model, in which bulk-oxide electron trapping/emission plays a major role, prohibits the direct use of causal theory over short time-scales, invalidating earlier theories on the subject. The work is extended to ESD stress of both polarities. Negative polarity ESD breakdownis found to be primarily oxide-voltage activated, with no significant dependence on temperature of luminosity. Positive polarity breakdown depends on the rate of surface inversion, dictated by the Si avalanche threshold and/or the generation speed of light-induced carriers. An analytical model, based upon the above theory is developed to predict ESD breakdown over a wide range of conditions. The thesis ends with an experimental and theoretical investigation of the effects of ESD breakdown on device and circuit performance. Breakdown sites are modelled as resistive paths in the oxide, and their distorting effects upon transistor performance are studied. The degradation of a damaged transistor under working stress is observed, giving a deeper insight into the latent hazards of ESD damage.

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