Nowadays, power electronic converters based exclusively on IGBTs seem to have achieved excellent load side performance up to megawatt powers range in the low voltage range (200-690Vrms) and are steadily gaining good performance in the medium voltage range as well. However, the medium and high voltage/high power range remains dominated by converters using naturally commutated thyristors, such as line-commutated cycloconverters, line-commutated current source inverters, which provide comparatively poorer output side performance. The purpose of this thesis is to investigate both the conventional cycloconverter, which will be referred as standard cycloconverter in the thesis, and the new hybrid cycloconverter topologies, which are capable of improving the performance of the standard cycloconverter by adding an auxiliary forced commutated inverter with reduced installed power. It will be shown that the new topology is not only able to improve the quality of the output voltage, but also to enhance the control over the circulating current and therefore, for some of the standard cycloconverter arrangements, to improve the input power quality. To realize the evaluation of the standard cycloconverter and validate the feasibility of the new hybrid cycloconverter in both circulating current and circulating current-free mode, SABER simulation models are developed in the first place to perform the initial analysis. A configurable three-phase input to three-phase output cycloconverter prototype which can be easily changed via a switch box to test four different cycloconverter topologies (standard and hybrid) is designed and implemented in the laboratory. Finally, the whole system is debugged and tested. All the relevant results obtained from both the simulation and experiment will be thoroughly analyzed in the thesis.

Digital filtering (DF) techniques are receiving significant interest, because they can represent fine features such as vias, thin-panels and thin-wires in full-field solutions of electromagnetic problems with significant savings in computational costs. However, a limitation of this technique is that DF can only represent a fine feature as a plane or as an internal boundary. In other words, an internal boundary can represent the electromagnetic properties of a fine feature in one dimension or two directions. The DF technique is usually involved with time domain solvers such as the Finite-difference time-domain (FDTD) and the Transmission Line Modeling (TLM) methods. Both of them are commonly used to investigate the electromagnetic fields in the problem spaces. Here the TLM method is selected for demonstrating the DF technique. This thesis presents the formulation of TLM in three-dimensions in order to investigate the limitations of the DF technique and the solutions. As a result, new techniques have been developed. These techniques can be applied to the three dimensional TLM method in order to represent the fine features in three-dimensions appropriately. The developed techniques were demonstrated using some examples of three-dimensional embedded objects, such as conducting volumes and dielectrics. Their accuracy and efficiency are compared with the standard TLM method in the time and frequency-domain. The results show good agreement between these techniques and the standard TLM method.

With the advantages of low cost, low power consumption, high reliability and potential for large scale integration, CMOS monolithically integrated active pixel chips have significant application in optical sensing systems. The optical front end presented in this thesis will have application in Optical Scanning Acoustic Microscope System (O-SAM), which involves a totally non-contact method of acquiring images of the interaction between surface acoustic waves (SAWs) and a solid material to be characterized. In this work, an ultra fast optical front-end using improved regulated cascade scheme is developed based on AMS 0.35mm CMOS technology. The receiver consists of an integrated photodiode, a transimpedance amplifier, a mixer, an IF amplifier and an output buffer. By treating the n-well in standard CMOS technology as a screening terminal to block the slow photo-generated bulk carriers and interdigitizing shallow p+ junctions as the active region, the integrated photodiode operates up to 4.9 GHz with no process modification. Its responsivity was measured to be 0.016 A/W. With multi-inductive-series peaking technique, the improved ReGulated-Cascade (RGC) transimpedance amplifier achieves an experimentally measured -3dB bandwidth of more than 6 GHz and a transimpedance gain of 51 dBW, which is the fastest reported TIA in CMOS 0.35mm technology. The 5 GHz Gilbert cell mixer produces a conversion gain of 11 dB, which greatly minimized the noise contribution from the IF stage. The noise figure and input IIP3 of the mixer were measured to be 15.7 dB and 1.5 dBm, respectively. The IF amplifier and output buffer pick up and further amplify the signal for post processing. The optical front end demonstrates a typical equivalent input noise current of 35 pA=pHz at 5 GHz, and a total transimpedance gain of 83 dB ohm whileconsuming a total current of 40 mA from 3.3 V power supply. The -3 dB bandwidth for the optical front end was measured to be 4.9 GHz. All the prototype chips, including the optical front end, and the individual circuits including the photodiode, TIA, mixer were probe-tested and all the measurements were taken with Anritsu VNA 37397D and Anritsu spectrum analyser MS2721A.

Characterization of electromagnetic emissions from printed circuit boards (PCBs) is an important issue in electromagnetic compatibility (EMC) design and analysis of modern electronic systems. This thesis is focused on the development of a novel modelling and characterization methodology for predicting the electromagnetic emissions from PCBs in both free space and closed environment. The basic idea of this work is to model the actual PCB radiating source with a dipole-based equivalence found from near-field scanning. A fully automatic near-field scanning system and scanning methodology are developed that provide reliable and sufficient data for the construction of equivalent emission models of PCB structures. The model of PCB emissions is developed that uses an array of equivalent dipoles deduced from magnetic near-field scans. Guidelines are proposed for setting the modelling configuration and parameters. The modelling accuracy can be improved by either improving the measurement efforts or using the mathematical regularization technique. An optimization procedure based on genetic algorithms is developed which addresses the optimal configuration of the model. For applications in closed environments, the equivalent model is extended to account for the interactions between the PCB and the enclosure. The extension comprises a dielectric layer and a ground plane which explicitly represent the necessary electromagnetic passive properties of a PCB. This is referred to as the dipole-dielectric-conducting plane (DDC) model and provides a completely general representation which can be incorporated into electromagnetic simulation or analysis tools. The modelling and characterization methodology provides a useful tool for efficient analysis of issues related to EMC design of systems with PCBs as regards predicting electromagnetic emissions in both free space and closed environment. The proposed method has significant advantages in tackling realistic problems because the equivalent models greatly reduce the computational costs and do no rely on the knowledge of detailed PCB structure.

The aim of the work presented in this thesis is to improve the operational reliability of a power module and increase the efficiency of its associated cooling system by integrating the design of the cooler as part of the module. Power modules are increasingly used in a variety of applications ranging from aircraft and mass transport systems, to motor control and power conversion in the home. Reliability of the power module is very important in aerospace applications where the highest levels of safety and robustness are required while keeping the volume and mass of the module as low as possible. Certain parts of the power module such as the solder layer beneath the silicon device and the substrate are prone to failure with thermal cycling. The layer of thermal grease between the baseplate of the module and the heatsink significantly increases the thermal resistance between the electronic devices and the coolant fluid. The power module can be constructed so that some of the interfaces within the module which are prone to failure are improved or completely removed from the assembly greatly reducing the thermal resistance from junction to ambient. The research identified cooling methods which are able to cope with the increasingly high heat fluxes produced by power electronic devices. Jet impingement cooling was selected for testing and further development. An initial series of tests confirmed that liquid jet impingement can be used to generate high heat transfer coefficients for the efficient cooling of power modules. Results from experimental tests showed that directly cooling the substrate tile with jet impingement resulted in the devices being cooled more effectively compared to the commonly used serpentine coldplate and a direct-baseplate cooled jet impingement system. It was postulated that more efficient cooling can be achieved by targeting the hotspots on the substrate beneath each device with a carefully designed impingement array. A test apparatus was constructed to test a variety of jet impingement arrays to confirm the hypothesis. A second test apparatus was constructed to characterise the performance of the jet arrays in more detail using a thermal imaging camera to monitor the surface temperature of a single device. An optimal jet configuration was found for the efficient cooling of a single device. The work concluded that an improvement in efficiency and reliability can be gained by constructing power modules with integrated jet impingement arrays direct-substrate cooling the hotspots beneath the devices.

Nowadays, there has been an increasing interest in Terahertz (THz) radiation for application across scientific disciplines including atmospheric sensing, medical diagnosis, security screening and explosive detection. The limitation of THz generators and detectors has gained interest from scientists and engineers to explore the development of both sources and detectors. With the advantages of low cost, low power consumption, high reliability and potential for large-scale integration, sub-THz generator and detector can be developed using CMOS process technology. In this thesis, an IMPATT diode acts as a sub-THz generator, HEMTs and MOSFETs act as sub-THz detectors, which are developed in AMS 0.35 μm CMOS technology and UMC, 0.18 μm CMOS technology. The size of the IMPATT diode was 120 μm x 50 μm with the target resonant frequency at 30 GHz. The experiment results show that the operating frequency of the IMPATT diode was between 12 GHz up to 14 GHz. Then by using HEMTs with 0.2 μm gate length and 200 μm gate widths, sub-THz radiation detection has been demonstrated. Experimental results show that the photoresponse depends on the drain current and the gate to source voltage VGS. In addition, photoresponse also depends on varying frequencies up to 220 GHz and fixed the drain current. Furthermore, the HEMT also give an indication of response by varying the input power of microwave extender. MOSFETs from two types of CMOS technology; AMS 0.35μm and UMC 0.18 μm technology with different gate length ranging from 180 nm up 350 nm were demonstrated. These results provide evidence that the photoresponse increases with the drain current and the RF input power, but inversely to the frequencies. These results also provide evidence that the MOSFETs are able to work as low cost and sensitive sub-THz detector.

The trajectory of the Taiwanese economy over past decades has reflected transitions in global geo-economy towards a vertical specialisation of global trade, knowledge-based competition, variation of industrialisation in the Third World, regional trisection of the world economy, etc. Its industry, making remarkable progress based on a long-term national assistance, is involved in the outward direct investment whereby overseas production is arranged. Such strategic actions of industrial capital slice through national boundaries and, meanwhile, incorporate state-business relationships on a broader scale at a national level. The thesis seeks to portray the transnationalisation of the Taiwanese IC sector through its specific organisational processes and spatial dynamics with an aim to understanding the way that indigenous firms are associated with the home state and the convergence of IC production systems on subnational, transnational and global scales. This work finds that the outward expansion of the IC industrial capital reflects a spatial trend converging on China, the Yangtze River Delta in particular, owing to a reshuffle of the global electronic production chain. However, flow of capital and material along the chain across the Taiwan Strait move along a circuitous route. It also finds that a persistent inter-state feud accounts for the domestic debates over the westward investment of the IC capital. There is tension between the neo-liberalist logic of business practices and national intervention in a guided capitalist stance. It underlines the conflicts of imperative territoriality. On the one hand, the firms recognise the necessity of stretching industrial territories to the Mainland in consideration of sectoral competitiveness. On the other hand, what the state is concerned with lies not only in the impacts of industrial de-territorialisation upon domestic industries but also in the result of over-dependence upon China that would incorporate national economy into economic territories of the Great China Circle.

The miniaturization trends on electronic components manufacturing, have challenged conventional knowledge on materials strength and deformation behavior. ”The smaller the stronger” has become a commonplace expression summarizing a multitude of experimental findings in micro-scale plasticity, and modelling tools capable of capturing this distinctive reality are in urgent demand. The thesis investigates the ubiquitous size effects in plastic deformation of micron-scale specimens. Tracing the source of such a behavior to the constituent elements of plastic deformation, we use as starting point the dynamics of discrete dislocations and try to embody them into a continuum framework. The thesis is structured in two independent parts. In the first part the question why size effects occur in constrained geometries is addressed. A systematic investigation of the connection between internal and external length scales is carried out in a system where dislocations, in the form of continuous lines embedded in a threedimensional isotropic medium, move, expand, interact, and thus create plastic distortion on the deforming body. Our modelling strategy utilizes a set of deterministic evolution equations on dislocation densities for describing the stress-driven evolution of the material’s internal state. These transport-like equations simultaneously serve the role of constitutive laws describing the deformation of the stressed body. Subsequent application to three benchmark problems is found to give good agreement both with experiment and discrete dislocation dynamics simulation. The second part of this thesis focuses on the heterogeneity and intermittency of deformation processes on the micro scale. Recent experimental results question the concept of smooth and homogeneous plastic flow with fluctuations that average out above a certain scale. Bursts of activity, which follow power-law size distributions and produce long-range correlated deformation patterns, seem to pertain even on scales far greater than the atomic one. In short, plasticity in this view appears as a ’crackling noise’ phenomenon similar to other irregular and burst-like processes such as earthquakes or granular avalanches. But then why do we witness smooth stress-strain curves on macroscopic sample testing? Concepts originating from Self Organized Criticality and pinning theories are employed for producing an efficient continuum description which is then used to study the effect of intrinsic and extrinsic deformation parameters on the fluctuation phenomena. It is deduced that hardening, load driving and specimen size, are all decisive on constraining fluctuating behavior, and limits of classical theory’s applicability can be drawn.

A new model for piezoelectric ultrasonic transducers is proposed. Using a systems engineering approach, the concept of feedback is used to explain secondary piezoelectric effects and to clearly describe electro-mechanical interaction. The model is derived from the fundamental piezoelectric equations and it embraces the relevant practical situations where the transducer is subject to arbitrary electrical and mechanical loading. The following main features are incorporated within the model. a - It is valid over a wide range of frequencies, b - It is applicable in both transmission and reception modes, c - It involves realisable elements which are readily simulated, and d - piezoelectric, pressure and voltage interactions are clearly related. The model has been verified extensively in computer simulations and water tank measurements of transducer profiles. Extremely close substantiation of the theoretical analyses was obtained, and the model is considered to offer significant advantages over existing transducer analogies.

A small, low-power Object-Oriented Programmable integrated circuit (OOPic) microcontroller was integrated and tested with the architecture for an autonomous ground vehicle (AGV). Sensors with the OOPic, and the XBee Wireless Suite were included in the integration. Tests were conducted, including range and time operation analysis for wireless communications for comparison with the legacy BL2000 microcontroller. Results demonstrated long battery life for the electronics of the robot, as well as communication ranges exceeding high power modems. The OOPic was limited by processing power and an ability to interpret some incoming form data. Consequently its use as a one for one replacement for the BL2000 is limited. However combined use with the BL2000 shows promise as a replacement for sensor monitoring and a hardware substitute for the legacy Pulse Width Modulator.