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This thesis presents a thorough analysis of the ring resonator, and studies the use of the ring at millimetre-wave frequencies (above 30GHz). An equivalent circuit for the ring is derived which is useful for extracting data from measured circuits, and accounts for different loss mechanisms and loading effects of the feed circuit. New analysis is presented on the effects of curvature, which is shown to influence the resonant frequencies and cause radiation which increases the loss in the ring.

The theme of this work has been multilayer microwave circuits, and. has focused on two aspects, namely multilayer interconnects and multilayer antennas. The report provides a detailed analysis of unwanted coupling in multilayer interconnections. New data are presented on the effects of coupling between conductors in highly integrated, multilayer circuits working at frequencies up to 100 GHz.

Modern fabrication processes offer the microwave and millimetre-wave circuit designers a wide range of techniques and materials for realising planar circuits. Consequently, an in-depth analysis of the materials properties and their influence on particular planar design is needed to support the design process. The outcome of the research described in this thesis provides microwave and millimetre circuit designers with information on microwave performance of thick film conductors on 96% alumina substrates.

This thesis introduces, for the first time, novel microwave circuits using ferrite left handed (LH) coplanar waveguide (CPW) metamaterials. Most commonly useful ferrite circuits such as impedance transformers, resonators, and couplers have been investigated. Compared to such conventional ferrite circuits, the proposed circuits are characterized by very compact size introducing small losses and wide operational bandwidth, novel propagation properties, in addition to new functionalities which are proposed here for the first time as well.

In this study techniques are developed for the analysis and design of piezoelectric sonar transducers based on equivalent circuit representations. For the purposes of analysis, equivalent circuits capable of accurately representing every element of a transducer in the full operating frequency range, are developed. The most convenient fashion in which these equivalents could be derived is also discussed. For the purposes of design the accurate equivalents are approximated by L-C-R circuits. The limits of both representations are discussed in detail. The technique of analysis developed is capable of determining the frequency characteristics as well as the transient response to any electrical or acoustic input which can be specified analytically or numerically in the time domain. The design technique is based on the formulation of a ladder-type generalized circuit incorporating the essential components of any transducer. The generalised circuit is then used to extract particular bandpass filter designs which possess wide passbands and which are mechanically realizable. By this procedure it is found possible to design transducers exhibiting bandwidths of around 100%. The performance of a 'test' transducer constructed to verify both analysis and design theories is also discussed.

Two 25 ns wideband HTS delay lines with a novel double-spiral meander line (DSML) structure are designed, fabricated and measured. One is based on the conventional coplanar waveguide (CPW), and the other based on a conductor-backed coplanar waveguide (CBCPW). Systematic design work is presented in this thesis on the calculations of transmission-line parameters, the selection and optimisation of delay line patterns, and the modelling of the transitions and connections at the input/output. Simulations show that the DSML structure has better transmission efficiency over a wide frequency range than the conventional double-spiral line (DSL). The bandwidth and dispersion of such a meander structure are investigated. The fabricated delay lines are first characterised as resonators with a fundamental mode at ~20 MHz. The surface resistances of the superconductors and the temperature- and power-dependent properties are investigated by measuring the Q-values of more than 1000 harmonics from 20 MHz to 20 GHz. Then, the delay lines are fully connected as they would be used in the application and measured thoroughly in both the frequency and time domain. The performance of the CBCPW delay line is the best ever demonstrated in terms of the widest resonance-free band (2 to 18 GHz), low insertion loss (0.06 dB/ns at 60 K and 10 GHz), small ripple (<1 dB up until 16 GHz), and small dispersion (< 2 ns in the variation of group delay between 2 and 18 GHz). This is the first coplanar delay line successfully demonstrated without using bonding-wires to join the in-plane grounds. The spurious reflecting elements in the DSML structure are identified by the time domain analyses. The results from this measurement are compared comprehensively with those from both resonance measurement and simulations.

SPICE, from the University of California, at Berkeley, is the de facto world standard for circuit simulation. SPICE is used to model the behaviour of electronic circuits prior to manufacturing to decrease defects and hence reduce costs. However, accurate SPICE simulations of today's sub micron circuits can often take days or weeks on conventional processors. In a nutshell, a SPICE simulation is an iterative process that consists of two phases per iteration, namely, model evaluation followed by a matrix solution. The model evaluation phase has been found to be easily parallelisable unlike the subsequent phase, which involves the solution of highly sparse and asymmetric matrices. In this thesis, we present an FPGA implementation of a sparse matrix solver hardware,geared towards matrices that arise in SPICE circuit simulations. As such, we demonstrate how we extract parallelism at di�erent granularities to accelerate the solution process. Our approach combines static pivoting with symbolic analysis to compute an accurate task ow-graph which e�ciently exploits parallelism at multiple granularities and sustains high oating-point data rates. We also present a quantitative comparison between the performance of our hardware protrotype and state-of-the-art software package running on a general purpose PC equipped with a 2.67 GHz six-core 12 thread Intel Core Xeon X5650 microprocessor and 6 GB memory. We report average speedups of 9.65�, 11.83�, 17.21� against UMFPACK, KLU, and Kundert Sparse matrix packages respectively. We also detail our approach to adapt our sparse LU hardware prototype from a single-FPGA architecture to a multi-FPGA system to achieve higher acceleration ratios up to 38� for certain circuit matrices.

Space charge has been recognized as an important factor contributing to the electrical failure of the cable insulation. Extensive efforts have been made to investigate space charge dynamics within polymeric insulations under electric stresses. Basic information about space charge has been recognized resorting to modern charge mapping techniques but the underlying mechanisms for charge transport, charge trapping characteristics are not yet well understood. Hence theoretical modelling and numerical simulation are employed to simulate the space charge and provide an insight into the charge distribution in dielectrics. This thesis comprises the quantitative analysis of space charge through numerical modelling and experimental investigations of charge trapping in polymeric insulation materials. A bipolar charge transport model which involves bipolar charge injection from the electrodes, charge transport with trapping and recombination in the bulk has been developed to simulate the dynamics of space charge in polyethylene. The build-up of space charge in polyethylene under dc electric fields has been modelled. The influence of parameters related to the properties of polyethylene on the formation of space charge has been recognized. Furthermore, this model is introduced to simulate the dynamics of corona charge decay in polyethylene. The formation of charge packets in polyethylene is also investigated using a numerical modelling approach. A fast pulsed electro-acoustic system along with a data processing program has been developed to investigate the behaviour of space charge in polyethylene under ac voltages. The understanding of space charge under ac stresses has also been simulated using the further developed bipolar charge transport model. Experiments and simulation have also been expanded into understanding electroluminescence, which is an indication of pre-aging of polymers under ac stress.