The stringent specifications of modern tracking systems demand antennas of high performance. For this reason arrays are finding increasing application as monopulse antennas. A new exact procedure is introduced for the synthesis of optimum difference distributions for linear arrays of discrete elements, with a maximum sidelobe level specification. The method is based on the Zolotarev polynomial, and is precisely the difference mode equivalent of the Dolph-Chebyshev synthesis for sum patterns. When the interelement spacings are a half-wavelength or larger the element excitations are obtained in a very direct manner from the Chebyshev series expansion of the Zolotarev polynomial. For smaller spacings, a set of recursive equations is derived for finding the array excitation set. Efficient means of performing all the computations associated with the above procedure are given in full. In addition, a set of design tables is presented for a range of Zolotarev arrays of practical utility. A novel technique, directly applicable to arrays of discrete elements, for the synthesis of high directivity difference patterns with arbitrary si delobe envelope tapers is presented. This is done by using the.Zolotarev space factor zeros and correctly relocating these in a well-defined manner to effect the taper. A solution to the direct synthesis of discrete array sum patterns with arbitrary sidelobe envelope tapers is introduced. In this case the synthesis is also done by correct placement of the space factor zeros. The above techniques enable high excitation efficiency, low sidelobe, sum and difference pat terns to be synthesized independently. Contributions to the simultaneous synthesis of sum and difference patterns, subject to specified array feed network complexity constraints, are also given. These utilise information on the excitations and space factor zeros of the independently optimal solutions, along with constrained numerical optimisation. The thesis is based on original research done by the author, except where explicit reference is made to the work of others.

A measure of ship speed is needed for dead reckoning navigation, docking, and as an input to satellite navigation systems. Ship speed is also used as an input to fire control systems on Naval vessels. The need for an accurate speed measuring device, that measures ship speed relative to the sea bed is thus apparent. All non acoustic logs measure ship speed relative to the water, and absolute ship speed can only be estimated if a knowledge of water currents is available. An acoustic log that provides an absolute measure of ship speed at limited operating depths is the Doppler log. For deep water the Doppler log measures speed relative to the water and it is thus affected by currents. A new development in acoustic logs is the correlation log. The correlation log can measure absolute speed at much greater depths than can the Doppler log. This is because it utilises a wide beam pointing vertically at the sea bed. The.wide beam permits a low operating frequency to be used which implies low attenuation. The high backscattering strength at normal angles of incidence combined with the low attenuation, means that relative to the Doppler log, the correlation log can measure absolute speed at much greater depths. The correlation log consists of a transmitter, which utilises tone burst transmission, and two or more receivers in line with the direction of motion. The signals received by two transducers will be similar except for a time shift 'T', which is given by the equation T = d/2V, where V is the speed and d the transducer separation. A device based on these principles has been built and tested. Results have shown that the system concepts are viable and will lead to an absolute speed measuring device that can operate at great depth.

Bibliography: pages 128-129. / A 9 phase transistor inverter fed induction motor for a battery vehicle with direct wheel drive is discussed. A new method of motor voltage control by pulse, width modulation, where the phases are interlaced in a manner to conserve continuity of the supply current, is described. In addition to this, a novel construction, where the motor and the inverter are built into one compact and economical unit, is presented.

Bibliography: pages 292-294. / Following the development of high speed solid state switches for the forced commutation of current in AC power circuits it has become feasible to apply forced commutation techniques to the frequency and voltage control of induction motors as variable speed drives. The availability of these methods raises questions regarding their effect on the performance of the motor and the generation of harmonic currents in the electrical supply. After the initial use of numerical simulation in the study of these systems it became apparent that this approach was not suitable for the evaluation of steady state performance factors. This thesis sets out to establish an analysis of the induction motor under these conditions which leads to the algebraic formulation of the performance of the system in the steady state. This approach can be used in any situation where the electrical supply to an induction motor is modulated by switching techniques. The analysis has been applied to chopper modulation of the supply voltage and also to a phase-stepping frequency convertor which incorporates chopper modulation. Experimental results are included to illustrate the validity of the analytical method.

No description available.

Bibliography: pages 107-108. / With the advancement of thyristor technology, variable speed alternating current drives are providing improved performance over conventional systems. The aim of this thesis is to investigate the possibilities of direct digital control of a thyristor converter and to determine the major parameters affecting the operation of a variable speed synchronous machine drive.

No description available.

This thesis will show how a new type of controller for a Nylon spinning machine was developed from an initial specification. The controller is a component in a loosely coupled feedback system which reads two tachometer pulse trains and various plant interlocks and produces two pulse trains which are used to control two solid state variable frequency variable voltage inverters and their AC motors. The specification calls for 24 controllers to be linked to a PDP 11/23 host computer which holds a library of operating parameters which can be downloaded into each control unit by ~n operator. After examining the requirements of the system, a microcomputer implementation was chosen as· best meeting the needs of the project. Elsewhere in the plant several earlier attempts at using micro-computers as dedicated controllers had been made, with rather poor results. Consideration of the future requirements of the company showed that there was a clear role for these controllers, and it was clear that there was a need to define standards for their development and implementation, and so a survey of the company's requirements was done, on the basis of which a standard was adopted. The thesis covers ali system related aspects of the project, from the initial selection of a microcomputer system and software development system to the design and implementation of the controller.

This thesis records the theoretical analysis and hardware development of a laboratory microwave imaging system which uses holographic principles. The application of an aperture synthesis technique and the electronic commutation of all antennae has resulted in a compact and economic assembly - which requires no moving parts and which, consequently, has a high field mapping speed potential. The relationship of this microwave holographic system to other established techniques is examined theoretically and the performance of the imaging system is demonstrated using conventional optically- and numerically-based reconstruction of the measured holograms. The high mapping speed potential of this system has allowed the exploitation of an imaging mode not usually associated with microwave holography. In particular, a certain antenna array specification leads to a versatile imaging system which corresponds closely in the laboratory scale to the widely used synthetic aperture radar principle. It is envisaged that the microwave holographic implementation of this latter principle be used as laboratory instrumentation in the elucidation of the interaction of hydrodynamic and electromagnetic waves. Some simple demonstrations of this application have been presented, and the concluding chapter also describes a suitable hardware specification. This thesis has also emphasised the hardware details of the imaging system since the development of the microwave and other electronic components represented a substantial part of this research and because the potential applications of the imaging principle have been found to be intimately linked to the tolerances of the various microwave components. Bibliography: pages 122-132.

Bibliography: pages 61-66. / This dissertation addresses system architecture concepts for the implementation of real-time distributed systems. In particular, it addresses the requirements of a specific mission and real-time critical distributed system application as this exemplifies most of the issues of concern. Of specific significance is the integration of real-time distributed data services into a platform-wide Information Management Infrastructure. The dissertation commences with an overview of the system-level allocated requirements. Derived requirements for an Information Management Infrastructure (IMI) are then determined. A generic system architecture is then presented in terms of the allocated and derived requirements. A specific topology, based on this architecture, as well as available technology, is described. The scalability of the architecture to -different platforms, including non-surface platforms, is discussed. As financial considerations are an important design driver and constraint, some anticipated order-of-magnitude system acquisition costs for a range of system complexities and configurations are briefly reviewed. Finally some conclusions and recommendations within the context of the allocated and derived requirements, as well as the RSA's politico-economic environment, are offered.