Abstract This thesis describes the design and implementation of a fully monolithic 10 Gb/s phase and frequency-locked loop based clock and data recovery (PFLL-CDR) integrated circuit, as well as the Verilog-A modeling of an asynchronous serial link based chip to chip communication system incorporating the proposed concept. The proposed design was implemented and fabricated using the 130 nm CMOS technology offered by UMC (United Microelectronics Corporation). Different PLL-based CDR circuits topologies were investigated in terms of architecture and speed. Based on the investigation, we proposed a new concept of quarter-rate (i.e. the clocking speed in the circuit is 2.5 GHz for 10 Gb/s data rate) and dual-loop topology which consists of phase-locked and frequency-locked loop. The frequency-locked loop (FLL) operates independently from the phase-locked loop (PLL), and has a highly-desired feature that once the proper frequency has been acquired, the FLL is automatically disabled and the PLL will take over to adjust the clock edges approximately in the middle of the incoming data bits for proper sampling. Another important feature of the proposed quarter-rate concept is the inherent 1-to-4 demultiplexing of the input serial data stream. A new quarter-rate phase detector based on the non-linear early-late phase detector concept has been used to achieve the multi-Giga bit/s speed and to eliminate the need of the front-end data pre-processing (edge detecting) units usually associated with the conventional CDR circuits. An eight-stage differential ring oscillator running at 2.5 GHz frequency center was used for the voltage-controlled oscillator (VCO) to generate low-jitter multi-phase clock signals. The transistor level simulation results demonstrated excellent performances in term of locking speed and power consumption. In order to verify the accuracy of the proposed quarter-rate concept, a clockless asynchronous serial link incorporating the proposed concept and communicating two chips at 10 Gb/s has been modelled at gate level using the Verilog-A language and time-domain simulated.

High Electron Mobility Transistors (HEMTs) are crucially important devices in microwave circuit applications. As the technology has matured, new applications have arisen, particularly at millimetre-wave and sub-millimetre wave frequencies. There now exists great demand for low-visibility, security and medical imaging in addition to telecommunications applications operating at frequencies well above 100 GHz. These new applications have driven demand for high frequency, low noise device operation; key areas in which HEMTs excel. As a consequence, there is growing incentive to explore the ultimate performance available from such devices. As with all FETs, the key to HEMT performance optimisation is the reduction of gate length, whilst optimally scaling the rest of the device and minimising parasitic extrinsic influences on device performance. Although HEMTs have been under development for many years, key performance metrics have latterly slowed in their evolution, largely due to the difficulty of fabricating devices at increasingly nanometric gate lengths and maintaining satisfactory scaling and device performance. At Glasgow, the world-leading 50 nm HEMT process developed in 2003 had not since been improved in the intervening five years. This work describes the fabrication of sub-25 nm HEMTs in a robust and repeatable manner by the use of advanced processing techniques: in particular, electron beam lithography and reactive ion etching. This thesis describes firstly the development of robust gate lithography for sub-25 nm patterning, and its incorporation into a complete device process flow. Secondly, processes and techniques for the optimisation of the complete device are described. This work has led to the successful fabrication of functional 22 nm HEMTs and the development of 10 nm scale gate pattern transfer: simultaneously some of the shortest gate length devices reported and amongst the smallest scale structures ever lithographically defined on III-V substrates. The first successful fabrication of implant-isolated planar high-indium HEMTs is also reported amongst other novel secondary processes.

This thesis has investigated the reduction of audible noise in low speed sensorless controlled drives for automotive electrical power steering (EPS) applications. The specific methods considered employ saliency tracking high frequency (hf) voltage injection in the machine's estimated d axis. In terms of the audible noise reduction, a novel random sinusoidal hf injection sensorless method has been proposed. The perceived audible noise due to the hf injection can be reduced by randomly distributing the injection frequencies around a centre frequency, such that it is perceived as a background hiss rather than the fixed tone heard with fixed hf injection methods. By analysing the A-weighting scales used to classify human perception of audible noise and frequency analysis of the recorded noise, an injection frequency of (lS00±328) Hz is found to have the lowest audible noise level compared to other random frequencies and other fixed frequencies methods. A 10 kHz square wave hf injection sensorless method has also been implemented. The frequency analysis of the recorded audible noise indicates that it also may be lower than for the fixed hf sinusoidal injection. In terms of control performance, sensorless torque control for these methods has been achieved from zero speed to ±240rpm with up to ±60A load (about 63% rated load). Similar position estimate quality has been demonstrated. Dynamic performance for a step change in torque current demand and for a speed reversal has been performed, and the random injection method with (1S00±328) Hz frequency has been found to be able to control a step change in torque demand current of 50A whilst for the 10kHz square wave injection method only a 40A step change can be achieved. On the other hand, the average position error after the speed transient has settled is less for the 10 kHz square ewave injection than for the random injection.

This thesis contains an account of research work carried out by the author at the Scottish Universities Research and Reactor Centre at East Kilbride, Scotland. The subject of the research was an investigation into the critical or limiting heat flux phenomenon under pool boiling; and confined boiling conditions. This phenomenon is of interest in the field of Nuclear Reactor Technology because it is a phenomenon that can limit the maximum power output of liquid cooled nuclear reactors. The research reported is divided into two sections, Part I dealing with the critical heat flux phenomenon for horizontally mounted heater specimen under pool boiling conditions and Part II dealing with the critical or limiting heat flux phenomenon for vertically mounted specimen under pool boiling and confined boiling conditions. In Part I both the rig and the heater assemblies were designed and commissioned by the author who also built the rig with Technician and Workshop assistance. The rig was operated by the author with Technician assistance and the experimental results were obtained by the author. The analysis, discussion and presentation of the results in Part I is due to the author and where these results are compared to other researchers work due recognition is given by an appropriate reference to the researcher involved. In Part II the rig and annuli heater assemblies were designed and commissioned by the author. The rig was also built by the author with Technician assistance. All the experimental results reported were obtained by the author with Technician assistance. Analysis, discussion and presentation of the results is due to the author. The theory developed in this part of the thesis is also mainly due to the author and where the author has drawn on the work of others this has been duly acknowledged in the text. The results of the horizontal pool boiling investigation reported in Part I tend to support the critical heat flux model due to Zuber (17,18) and to show that this model is still applicable to results obtained under vacuum conditions. HowThis thesis contains an account of research work carried out by the author at the Scottish Universities Research and Reactor Centre at East Kilbride, Scotland. The subject of the research was an investigation into the critical or limiting heat flux phenomenon under pool boiling; and confined boiling conditions. This phenomenon is of interest in the field of Nuclear Reactor Technology because it is a phenomenon that can limit the maximum power output of liquid cooled nuclear reactors. The research reported is divided into two sections, Part I dealing with the critical heat flux phenomenon for horizontally mounted heater specimen under pool boiling conditions and Part II dealing with the critical or limiting heat flux phenomenon for vertically mounted specimen under pool boiling and confined boiling conditions. In Part I both the rig and the heater assemblies were designed and commissioned by the author who also built the rig with Technician and Workshop assistance. The rig was operated by the author with Technician assistance and the experimental results were obtained by the author. The analysis, discussion and presentation of the results in Part I is due to the author and where these results are compared to other researchers work due recognition is given by an appropriate reference to the researcher involved. In Part II the rig and annuli heater assemblies were designed and commissioned by the author. The rig was also built by the author with Technician assistance. All the experimental results reported were obtained by the author with Technician assistance. Analysis, discussion and presentation of the results is due to the author. The theory developed in this part of the thesis is also mainly due to the author and where the author has drawn on the work of others this has been duly acknowledged in the text. The results of the horizontal pool boiling investigation reported in Part I tend to support the critical heat flux model due to Zuber (17,18) and to show that this model is still applicable to results obtained under vacuum conditions. HowThis thesis contains an account of research work carried out by the author at the Scottish Universities Research and Reactor Centre at East Kilbride, Scotland. The subject of the research was an investigation into the critical or limiting heat flux phenomenon under pool boiling; and confined boiling conditions. This phenomenon is of interest in the field of Nuclear Reactor Technology because it is a phenomenon that can limit the maximum power output of liquid cooled nuclear reactors. The research reported is divided into two sections, Part I dealing with the critical heat flux phenomenon for horizontally mounted heater specimen under pool boiling conditions and Part II dealing with the critical or limiting heat flux phenomenon for vertically mounted specimen under pool boiling and confined boiling conditions. In Part I both the rig and the heater assemblies were designed and commissioned by the author who also built the rig with Technician and Workshop assistance. The rig was operated by the author with Technician assistance and the experimental results were obtained by the author. The analysis, discussion and presentation of the results in Part I is due to the author and where these results are compared to other researchers work due recognition is given by an appropriate reference to the researcher involved. In Part II the rig and annuli heater assemblies were designed and commissioned by the author. The rig was also built by the author with Technician assistance. All the experimental results reported were obtained by the author with Technician assistance. Analysis, discussion and presentation of the results is due to the author. The theory developed in this part of the thesis is also mainly due to the author and where the author has drawn on the work of others this has been duly acknowledged in the text. The results of the horizontal pool boiling investigation reported in Part I tend to support the critical heat flux model due to Zuber (17,18) and to show that this model is still applicable to results obtained under vacuum conditions. However the results also show some limitations to this 'hydrodynamic' model in the sense that reduced heat fluxes were obtained as the heater tube wall thickness was reduced and also for heaters with contaminated surfaces. Neither of these effects are predicted by the Zuber model although the recent approach to this problem due to Ouwerkerk (13) could form a basis for taking account of the wall thickness effect. The results of the vertical heater-annular geometry investigation reported in Part II of this thesis have been successfully correlated and compared with the predictions of the theoretical model developed. Both the results for saturated liquid entry and for subcooled liquid entry to the annulus have been found to be compatible with the theoretical model predictions.

Over the past forty years the development of CMOS has been able to follow Moore’s law using planar silicon technology. However, this technology is reaching its limits as the density of transistors has a significant impact on the power dissipation in an integrated circuit. Alternative channel materials and device architectures will then be required in the future to reduce the power consumption of transistors. The development of CMOS technology with high mobility channel materials, specifically Ge for pMOS and III-V materials for nMOS, was the aim of the European Union FP7 funded Duallogic consortium, of which this project was part. The experimental work at the University of Glasgow was the III-V compound semiconductor MOSFET, in particular the study of Si processing compatible source/drain contacts to III-V MOSFET devices with InxGa1-xAs channel materials, which was an important aspect of this thesis. Another area investigated in this thesis is the impact of current crowding effects on source/drain contact resistance by aggressive scaling of devices. During this thesis, optimisation of a PdGe-based ohmic contact to buried channel device material with a In0.75GaAs channel led to a contact resistance of 0.15Ohm.mm compared to 1Ohm.mm in previous work by R. Hill. The PdGe-based contact also proved to be scalable in both vertical and lateral dimensions. This scaled structure was then integrated in a surface channel MOSFET device with 1μm access regions and gate lengths varying from 100nm to 20μm. The performance of the devices with 20μm gate lengths was then compared to devices with a NiGeAu based ohmic contact. An increase in RC, 1.82Ohm.mm vs. 0.94Ohm.mm, and Ron, 11.1Ohm.mm vs. 8.55Ohm.mm, was observed in the PdGe-based contact, which resulted in a decrease in gm, 92.3mS/mm vs. 103mS/mm, and Id,sat, 103mA/mm vs. 122mA/mm. However, further optimisation of the PdGe-based ohmic contact showed promising results with a contact resistance of 0.45Ohm.mm. The novel test structure is the first test structure, which makes direct contact to III-V material, with critical dimensions below the transfer length. This structure is able to experimentally observe the current crowding effects and allows for the extraction of the sheet resistance underneath the contact and a more accurate extraction of the specific contact resistivity. This offers a significant insight into the impact of the sheet resistance underneath the contact and the role it plays.

This thesis considers the design and implementation of passive wireless microwave readable pressure sensors on a single chip. Two novel-all passive devices are considered for wireless pressure operation. The first device consists of a tuned circuit operating at 10 GHz fabricated on SiO2 membrane, supported on a silicon wafer. A pressure difference across the membrane causes it to deflect so that a passive resonant circuit detunes. The circuit is remotely interrogated to read off the sensor data. The chip area is 20 mm2 and the membrane area is 2mm2 with thickness of 4 µm. Two on chip passive resonant circuits were investigated: a meandered dipole and a zigzag antenna. Both have a physical length of 4.25 mm. the sensors show a shift in their resonant frequency in response to changing pressure of 10.28-10.27 GHz for the meandered dipole, and 9.61-9.58 GHz for the zigzag antenna. The sensitivities of the meandered dipole and zigzag sensors are 12.5 kHz and 16 kHz mbar, respectively. The second device is a pressure sensor on CMOS chip. The sensing element is capacitor array covering an area of 2 mm2 on a membrane. This sensor is coupled with a dipole antenna operating at 8.77 GHz. The post processing of the CMOS chip is carried out only in three steps, and the sensor on its own shows a sensitivity of 0.47fF/mbar and wireless sensitivity of 27 kHz/mbar. The MIM capacitors on membrane can be used to detune the resonant frequency of an antenna.

Due to quiet operation, no moving parts, long lifespan and compact structure, the thermoelectric application has become a potential green technology which has been used in different areas in the efforts of contributing to achieve simplified and compact system structures and environmental friendliness. Its applications cover a wide range from the earliest application on kerosene lamp to aerospace applications, transportation tools, industrial utilities, medical services, electronic devices and temperature detecting & measuring facilities. Its disadvantage lies in the low conversion efficiency which only converts small amount (for Bi2Te3, up to 5%) of harvested energy to electrical power. It makes the use of the TEG system far from being economically feasible due to long cost recovery period. Consequently, its use is limited to specialised area where it is unnecessary to consider the cost of the thermal energy input and system cost recovery. This research aims to explore a way of widening the application range of thermoelectric generation based on introducing a potential direction of improving energy utilisation efficiency to a higher level by adopting thermoelectric cogeneration concept in residential house. It focuses on investigating the practicality of using thermoelectric applications in domestic sectors where the large amount of heat is exhausted to environment without being used and developing thermoelectric cogeneration system to generate electricity and produce pre-heated water for domestic use by recovering the waste heat from the domestic boiler and utilising the on-site solar energy. With the conversion efficiency given by the current commercially available thermoelectric modules, the optimised heat exchanging regimes and systems for thermoelectric applications have been comprehensively studied from the aspects of system design, integration, experimental study, numerical simulation and modification. The importance and necessity of effective heat exchanging methods have been emphasised by the experimental and numerical proofs for the development of a domestic thermoelectric cogeneration system with higher thermal efficiency. The impacts of this domestic energy solution have been evaluated from the aspects of the improvement for outdoor environment and indoor energy profile, as well as economic benefit. For the flue gas heat exchanger, the model with sudden expansion and gradual constriction has been identified gives in terms of overall performance. The model with sudden expansion, gradual constriction and staggered pipe layout and the one with sudden expansion, gradual constriction and inline pipe layout show better overall performance than other models. Among these two models, the one with staggered pipe layout shows better performance than the one with inline pipe layout in the velocity range of 3.6m/s-5m/s, whilst the one with inline pipe layout shows better performance between 0-3.6m/s. For the cold side heat exchanger, the one with four ø5mm branch channel angled at 90 against the main channel delivers the best overall performance out of 9 cooling plates built according to three variables. Experimental studies show the one-stage TCS produces more power than the two-stage TCS does when the heat input is supplied at 47W and 60W. As the heat input increases, the power output of two-stage TCS gets closer to that of one-stage TCS. In the system construction and assembly, uneven assembly can lead to a 20% drop in conversion efficiency. The pressure load at 18lpsi gives the highest power output out of five load values, which are 136psi, 159psi, 181psi, 204psi and 227psi, respectively. In comparison with individual assembly, module thickness difference in whole assembly degrades the system conversion efficiency. The cost recovery period of deploying this system in a residential house installed with a 24kW boiler and a 1 m2 solar collector has been evaluated. Based on the conversion efficiency and thermal efficiency that is 4% and 67% at 130C temperature difference. the house can produce 98W electricity and 1640W useable heat when the boiler is running and the contribution from the solar energy is included. It takes less than 4.2 years to recover the system cost.

The advent of deregulated electricity and the call for sustainable energy practices are major drivers for the continued increase of renewable energy systems within the modern day power network. Dominant among them is the wind energy system whose output is uncertain because of its dependence on the prevailing climatic conditions. This increases the level of uncertainty witnessed within the power system as such, as the penetration of renewable energy systems continue to increase, their effects cannot be trivialised. Probabilistic load flow (PLF) is employed by power system analysts to account for the effect of uncertainty within the power network. The common technique which is based on Monte Carlo Simulation (MCS), though accurate is very time consuming and for large systems it becomes unwieldy. Alternative approaches with the advantages of the MCS method but with reduced computational burden are required. A viable alternative method should therefore require minimum computational time and burden, be able to accurately model various network uncertainties, be applicable to practical small and large systems, be able to account for the effect of dependency among network variables and possess good overall accuracy. This thesis proposes a novel approximate approach referred to as the enhanced unscented transform method to meet the requirements of PLF. The method combines the Gaussian quadrature method and the Stieljes procedure with dimension reduction technique in deciding estimation points while the Cholesky decomposition is incorporated to account for the effect of dependency. The performance of the proposed technique is demonstrated using modified IEEE 6, 14, and 118 test systems and a practical distribution test system all incorporating wind farms. Results obtained for numerous scenarios show a good match between the proposed method and the MCS method but with significant computational burden saving. The performance of the method is also shown to compare favourably with other existing PLF methods.

This thesis describes the development and characterisation of a variety of novel capacitive ultrasonic transducers for use in air-coupled and immersion applications. The first sections of this thesis examine the fabrication and initial characterisation of novel fully micromachined transducers. These devices, produced using a silicon surface micromachining process, consisted of a large laterally dimensioned (up to 5mm square), silicon nitride membrane, typically O.S-2I1m in thickness, above a nominal 211m air gap. Typical operation in air was observed in the MHz region. The effects of membrane thickness and size were studied, as well as the effect of applied bias voltage. Differences between batches of devices were investigated. Their dynamic membrane displacements were measured using interferometric techniques. When driven with transient voltages typical displacements of a few nm were observed. Their radiated fields were also investigated, and compared to plane piston approximations, calculated with a Matlab™ program. Good agreement was found. This thesis also describes the development and characterisation of three novel aircoupled focusing transducers. Two of these devices utilised shaped backplates, one being cylindrically concave, and the other conically concave, to produce lines of focus. The third device utilised an off-axis parabolic mirror to produce a point of focus. The development and characterisation of each is described. Their frequency responses were measured, and found to be comparable with similar planar transducers. Experiments were devised to measure their vertical and lateral resolutions, the latter typically being found to be approximately a wavelength of their centre operating frequency (-500kHz). Their radiated peak sound pressure fields were measured, and for the cylindrical and conical device compared to theoretical plane piston approximations calculated with a Matlab™ program, with good agreement of form being found. Finally, all three transducers were used to create 3-D images of a two pence coin, using amplitude and time of arrival data. Reasonable images resulted. The final section. examines the development of an immersion transducer. This was characterised as both source and receiver, showing increases in both bandwidth and frequency response than when used in air. The effects of backplate surface properties on the characteristics of the device were studied. using a range of roughened, polished, and photolithographic metallic backplates. In addition, the effect of applied bias was also investigated. Sound pressure fields were measured, using both broadband and narrowband tone burst excitations. and compared to theoretical predictions from plane piston theory. These were calculated using a Matlab™ program, with good agreement found. The transducer was then used to produce pulse-echo C-scan images of artificially induced machined defects in Perspex and aluminium plates. Excellent images resulted.

This thesis examines the effects of burrs on performance of transformer cores through application of artificial burrs, measurements of overall specific total loss and local specific total loss, measurements of flux density redistribution caused by burrs and through development of eddy current loss model incorporating two dimensional eddy current losses and flux density distribution within a conductive sample. A clamping system was designed for application of artificial burrs in a completely repeatable and reversible manner. Various burr sizes and arrangements were investigated to confirm the effect and show the extent of the effect for different scenarios with the experimental core magnetised in the range of 0.1 T to 1.8 T. It was observed that for large number of laminations affected by the artificial burrs the overall core losses of the three phase, 350 kVA distribution transformer doubled while the local losses in the vicinity of the burred region reached over 1 kW/kg. Three eddy current loss models were developed in this investigation. One for a symmetrical case of burrs located on either edge of a stack of laminations, one for a non symmetrical case of burrs located on the edge or within the stack of laminations and finally, one taking into account flux density decay within a conductive material. A secondary objective of this thesis is a feasibility study of using thin film sensors within a commercial size transformer core. This was achieved by adapting a physical vapour deposition system to accommodate large laminations and depositing thin film needle sensors for flux density measurement and thin film thermocouples for loss measurement inside a stack of the core. The flux density measurement by thin film needle sensors within the core was successful. Thin film thermocouples did not provide successful results and the development of this part of the work is suggested as future work.