<p>This thesis demonstrates the high- level modelling and design of oversampled delta- sigma noise shapers for D/A conversion. It presents an overview and study on digital- to- analog converters (DAC) followed by the noise shapers. It helps us to understand how to design a noise shaper model and algorithmic expressions are presented. The models are verified through high level simulations. The usage of models is to reduce the design time and get a good understanding for fundamental limitations on performance. Instead of time consuming circuit- level simulations, we point out the behavioural- level and algorithmic- level simulations of the noise shaper and the entire system comprising of interpolation filter, noise shaper followed by pulse amplitude modulation and reconstruction filtering. We have used the delta- sigma modulators to reduce the number of bits representing the digital signal. It is found that the requirement on oversampled DACs are tough. It is emphasised that the design of an oversampling converter is a filter designproblem. There is a large number of trade- offs that can be made between the different building blocks in the OSDAC.</p>

<p>Using an array synthesis tool based on a modified differential evolution algorithm, it is shown that the position-phase synthesis exhibits improved pattern characteristics compared to both the phase only and position only synthesis of uniform amplitude antenna arrays. The design of an unequally spaced planar reflect-array and an active power combining reflect-array are presented. The unit cell of the active reflect-array consists of an amplifying active reflect-antenna designed using a novel dual polarized microstrip-T coupled patch antenna. Two modelling approaches are proposed for the active reflect-antenna and the modelling methods are compared with the experiments.</p><p>A computationally efficient analysis of an H-slot in the ground plane of a microstripline is carried out using a transmission line model. To improve the accuracy in the resonant region of the H-slot and retaining the computational efficiency, an artificial neural network is combined with an efficient spectral domain method. An efficient analysis tool for a silicon micromachined H-slot coupled antenna is developed by combining the transmission line models of the H-slot and an aperture coupled antenna. The experimental results are compared with the theory showing good agreement.</p><p>The analysis and design of a microwave amplifier based on non-resonant slot matching is carried out. It is seen that the designed slot matched amplifier has decreased layout size, improved gain and noise figure characteristics compared to a stub matched amplifier. An efficient method for the analysis of non-resonant slots is compared with other approaches showing good agreement. This points to the fact that non-resonant slot matched circuits can be designed with the same speed and efficiency as we design the traditional stub based matching circuits.</p><p>To address the problem of bandwidth and performance of reflect-arrays we propose a dielectric resonator antenna with slotline stubs. As a preliminary step we design a dielectric resonator antenna with slotline feed and the experimental results are compared with those of a commercial CAD tool. Design and analysis of 3D interconnects based on non-radiative dielectric waveguides is carried out. At millimeterwave, these interconnects are useful for hybrid and multilayer integration techniques.</p>

The continuing shrinkage of semiconductor devices towards nanoscale features and increased functionality has prompted a strong need for high-resolution characterization tools capable of mapping the electrical properties with nanoscale lateral resolution. In this regard, scanning capacitance microscopy (SCM) scanning spreading resistance microscopy (SSRM) and Kelvin probe force microscopy (KPFM) have emerged as powerful techniques. This thesis focuses on new applications of these techniques for the electrical characterization of III-V materials, devices and low-dimensional systems. One example is the investigation of GaAs/AlGaAs buried-heterostructure lasers with cross-sectional SCM. Several important issues have been addressed: nanoscale contrast related to local band structure, characterization of interfaces and evaluation of electrical properties of the regrown layers. These investigations demonstrate the ability of SCM for reliable, non-destructive and high resolution analysis of opto-electronic devices. Applications of SCM and SSRM as potential in-line evaluation tool for III-V processing are demonstrated. In this scope, the first work deals with the characterization of ion beam implanted InP, a promising approach to achieve ultrashort carrier lifetimes. The changes in the local electrical properties of this material induced by annealing are tracked. SCM and SSRM measurements were crucial in identifying the local regions of different conductivity due to the non-uniform damage profiles. The results are correlated with those obtained by complementary structural, electrical and optical characterization. The second work in this category establishes the utility of SCM for evaluating the impact of dry etching on the electrical properties of InP. The highly conductive nature of the near surface damaged layer and its subsequent recovery upon annealing is evidenced. A striking correlation between the SCM signal distributions and the ideality factors of macroscopic Schottky contact is observed. The last part deals with the electrical characterization of low-dimensional systems using SCM, SSRM and KPFM. The challenging issues motivating this work are the detection and quantification of confined carriers, the determination of band-offsets and the determination of the spatial resolution of the technique employed. The ability of SCM, SSRM and KPFM to detect carriers accumulated in InGaAs/InP quantum wells (QWs) is demonstrated. In each of these techniques, the physical mechanisms behind the contrast characteristic obtained at QWs are elucidated. The specific issues relating to the determination of the band-offsets are discussed. A new method to determine the "electrical" spatial resolution of SCM and SSRM is addressed using quantum well structures with varying inter-well spacings. Using commercial probes, sub-30 nm and sub-5 nm lateral resolution are determined for SCM and SSRM, respectively. The experimental conditions to perform high resolution measurements are identified.

Using an array synthesis tool based on a modified differential evolution algorithm, it is shown that the position-phase synthesis exhibits improved pattern characteristics compared to both the phase only and position only synthesis of uniform amplitude antenna arrays. The design of an unequally spaced planar reflect-array and an active power combining reflect-array are presented. The unit cell of the active reflect-array consists of an amplifying active reflect-antenna designed using a novel dual polarized microstrip-T coupled patch antenna. Two modelling approaches are proposed for the active reflect-antenna and the modelling methods are compared with the experiments. A computationally efficient analysis of an H-slot in the ground plane of a microstripline is carried out using a transmission line model. To improve the accuracy in the resonant region of the H-slot and retaining the computational efficiency, an artificial neural network is combined with an efficient spectral domain method. An efficient analysis tool for a silicon micromachined H-slot coupled antenna is developed by combining the transmission line models of the H-slot and an aperture coupled antenna. The experimental results are compared with the theory showing good agreement. The analysis and design of a microwave amplifier based on non-resonant slot matching is carried out. It is seen that the designed slot matched amplifier has decreased layout size, improved gain and noise figure characteristics compared to a stub matched amplifier. An efficient method for the analysis of non-resonant slots is compared with other approaches showing good agreement. This points to the fact that non-resonant slot matched circuits can be designed with the same speed and efficiency as we design the traditional stub based matching circuits. To address the problem of bandwidth and performance of reflect-arrays we propose a dielectric resonator antenna with slotline stubs. As a preliminary step we design a dielectric resonator antenna with slotline feed and the experimental results are compared with those of a commercial CAD tool. Design and analysis of 3D interconnects based on non-radiative dielectric waveguides is carried out. At millimeterwave, these interconnects are useful for hybrid and multilayer integration techniques.

This thesis demonstrates the high- level modelling and design of oversampled delta- sigma noise shapers for D/A conversion. It presents an overview and study on digital- to- analog converters (DAC) followed by the noise shapers. It helps us to understand how to design a noise shaper model and algorithmic expressions are presented. The models are verified through high level simulations. The usage of models is to reduce the design time and get a good understanding for fundamental limitations on performance. Instead of time consuming circuit- level simulations, we point out the behavioural- level and algorithmic- level simulations of the noise shaper and the entire system comprising of interpolation filter, noise shaper followed by pulse amplitude modulation and reconstruction filtering. We have used the delta- sigma modulators to reduce the number of bits representing the digital signal. It is found that the requirement on oversampled DACs are tough. It is emphasised that the design of an oversampling converter is a filter designproblem. There is a large number of trade- offs that can be made between the different building blocks in the OSDAC.

<p>When the Swedish electricity market was re-regulated in 1996 the trading with electricity was exposed to competition and the net service henceforth should be comprised by a monopoly comprised by a regulation. The regulation was based on a review of the costs of the network companies. No attention were paid to if the network was efficient. The following years many of the networks were sold from the municipalities to power companies, to increasing merger prices. The increasing prices in the mergers were followed by increasing prices to the subscribers of the network services. The regulator tried to stop the fast increasing prices, but didn’t succeed. The regulation paradigm couldn’t face the new realities and had to be revised.</p><p>In 1998 the author of this thesis was commissioned by the Swedish Regulator to propose a new regulation model for the Swedish grid companies. Existing models were reviewed but none of them fulfilled the requirements from the regulator; to be self-regulating and give incentives to improved efficiency and distribution reliability. Therefore a new approach was launched. The new approach was to change perspective from a company focus to a consumer focus – a performance-based regulation.</p><p>The solution was to base the regulation of the creation of a standard asset, a Reference Network. From this a new model – the Network Performance Assessment Model (NPAM) – was defined. The Reference Network is defined by four definitions, concerning the elements and topology of a Reference Network, the Subscriber Requirements and the Objective Prerequisites. These definitions grants the transparency of the model.</p><p>The model is sharp and is run into operation in 2004. The final test of the model indicated that the Swedish network companies are overcharging their subscribers with approximately 20%.</p><p>This thesis is an explanation of the model and the definitions, and a review of the thoughts and research which formed the model. Moreover there is a discussion of some topics reported by others in articles about the model. Finally in the conclusion there are topics of simplicity and transparency.</p>

<p>The continuing shrinkage of semiconductor devices towards nanoscale features and increased functionality has prompted a strong need for high-resolution characterization tools capable of mapping the electrical properties with nanoscale lateral resolution. In this regard, scanning capacitance microscopy (SCM) scanning spreading resistance microscopy (SSRM) and Kelvin probe force microscopy (KPFM) have emerged as powerful techniques. </p><p>This thesis focuses on new applications of these techniques for the electrical characterization of III-V materials, devices and low-dimensional systems. One example is the investigation of GaAs/AlGaAs buried-heterostructure lasers with cross-sectional SCM. Several important issues have been addressed: nanoscale contrast related to local band structure, characterization of interfaces and evaluation of electrical properties of the regrown layers. These investigations demonstrate the ability of SCM for reliable, non-destructive and high resolution analysis of opto-electronic devices. </p><p>Applications of SCM and SSRM as potential in-line evaluation tool for III-V processing are demonstrated. In this scope, the first work deals with the characterization of ion beam implanted InP, a promising approach to achieve ultrashort carrier lifetimes. The changes in the local electrical properties of this material induced by annealing are tracked. SCM and SSRM measurements were crucial in identifying the local regions of different conductivity due to the non-uniform damage profiles. The results are correlated with those obtained by complementary structural, electrical and optical characterization. The second work in this category establishes the utility of SCM for evaluating the impact of dry etching on the electrical properties of InP. The highly conductive nature of the near surface damaged layer and its subsequent recovery upon annealing is evidenced. A striking correlation between the SCM signal distributions and the ideality factors of macroscopic Schottky contact is observed. </p><p>The last part deals with the electrical characterization of low-dimensional systems using SCM, SSRM and KPFM. The challenging issues motivating this work are the detection and quantification of confined carriers, the determination of band-offsets and the determination of the spatial resolution of the technique employed. The ability of SCM, SSRM and KPFM to detect carriers accumulated in InGaAs/InP quantum wells (QWs) is demonstrated. In each of these techniques, the physical mechanisms behind the contrast characteristic obtained at QWs are elucidated. The specific issues relating to the determination of the band-offsets are discussed. A new method to determine the "electrical" spatial resolution of SCM and SSRM is addressed using quantum well structures with varying inter-well spacings. Using commercial probes, sub-30 nm and sub-5 nm lateral resolution are determined for SCM and SSRM, respectively. The experimental conditions to perform high resolution measurements are identified.</p>

<p>This study was initiated to investigate if it could be feasible to supply offshore oil installations in the North Sea with electrical power from land. A prestudy of alternative converter topologies indicated that the most promising solution would be to investigate a conventional system with reduced synchronous compensator rating.</p><p>The study starts with a summary of the state of power supply to offshore installations today, and a short review of classical HVDC transmission. It goes on to analyse how a passive network without sources influences the inverter. The transmission, with its current controlled rectifier and large inductance, is simulated as a current source. Under these circumstances the analysis shows that the network frequency has to adapt in order to keep the active and reactive power balance until the controllers are able to react. The concept of firing angle for a thyristor is limited in a system with variable frequency, the actual control parameter is the firing delay time.</p><p>Sensitivity analysis showed some astonishing consequences. The frequency rises both by an increase in the active and in the reactive load. The voltage falls by an increase in the active load, but rises by an increase in the inductive load.</p><p>Two different control principles for the system of inverter, synchronous compensator and load are defined. The first takes the reference for the firing delay time from the fundamental voltage at the point of common coupling. The second takes the reference for the firing delay time from the simulated EMF of the synchronous compensator. Of these, the second is the more stable and should be chosen as the basis for a possible control system.</p><p>Two simulation tools are applied. The first is a quasi-phasor model running on Matlab with Simulink. The other is a time domain model in KREAN. The time domain model is primarily used for the verification of the quasi-phasor model, and shows that quasi-phasors is still a valuable tool for making a quick analysis of the main features when the details of the transients are of less importance.</p><p>The study indicates that power supply by HVDC transmission from land to offshore oil installations could be technically feasible, even without the large synchronous compensators normally required. It has been shown that in a network only supplied by an inverter, variations of active and reactive loads have significant influence on both voltage and frequency. Particularly it should be noted that the frequency shows a positive sensitivity to increases in load. This could make the system intrinsically unstable in the case of a frequency dependent load such as motors.</p><p>It was not a part of the study to optimize controllers, but even with simple controllers it was possible to keep the frequency within limits given by norms and regulations, but the voltages were dynamically outside the limits, though not very far. These voltage overswings take place in the first few instances after a disturbance, so it takes unrealistically fast controllers to handle them. They are partly due to the model, where the land based rectifier and the DC reactors are simulated by a constant current source, but partly they have to be handled by overdimensioning of the system.</p><p>The simulations indicate that it should be technically possible to supply an oil platform with electrical power from land by means of HVDC transmission with small synchronous compensators. Whether this is financially feasible has not been investigated. Neither has it been considered whether the necessary equipment can actually be installed on an oil platform.</p><p>Recently both ABB and Siemens have presented solutions for HVDC transmission in the lower and medium power range based on voltage source converters based on IGBTs. Fully controllable voltage source HVDC converters have properties that may be better suited than conventional line commutated current source thyristor inverters, to supply weak or passive networks, such as offshore oil installations, with electrical power. But they also have some disadvantages, and a complete technical and financial comparison must be performed in order to decide about any potential project.</p>

This study was initiated to investigate if it could be feasible to supply offshore oil installations in the North Sea with electrical power from land. A prestudy of alternative converter topologies indicated that the most promising solution would be to investigate a conventional system with reduced synchronous compensator rating. The study starts with a summary of the state of power supply to offshore installations today, and a short review of classical HVDC transmission. It goes on to analyse how a passive network without sources influences the inverter. The transmission, with its current controlled rectifier and large inductance, is simulated as a current source. Under these circumstances the analysis shows that the network frequency has to adapt in order to keep the active and reactive power balance until the controllers are able to react. The concept of firing angle for a thyristor is limited in a system with variable frequency, the actual control parameter is the firing delay time. Sensitivity analysis showed some astonishing consequences. The frequency rises both by an increase in the active and in the reactive load. The voltage falls by an increase in the active load, but rises by an increase in the inductive load. Two different control principles for the system of inverter, synchronous compensator and load are defined. The first takes the reference for the firing delay time from the fundamental voltage at the point of common coupling. The second takes the reference for the firing delay time from the simulated EMF of the synchronous compensator. Of these, the second is the more stable and should be chosen as the basis for a possible control system. Two simulation tools are applied. The first is a quasi-phasor model running on Matlab with Simulink. The other is a time domain model in KREAN. The time domain model is primarily used for the verification of the quasi-phasor model, and shows that quasi-phasors is still a valuable tool for making a quick analysis of the main features when the details of the transients are of less importance. The study indicates that power supply by HVDC transmission from land to offshore oil installations could be technically feasible, even without the large synchronous compensators normally required. It has been shown that in a network only supplied by an inverter, variations of active and reactive loads have significant influence on both voltage and frequency. Particularly it should be noted that the frequency shows a positive sensitivity to increases in load. This could make the system intrinsically unstable in the case of a frequency dependent load such as motors. It was not a part of the study to optimize controllers, but even with simple controllers it was possible to keep the frequency within limits given by norms and regulations, but the voltages were dynamically outside the limits, though not very far. These voltage overswings take place in the first few instances after a disturbance, so it takes unrealistically fast controllers to handle them. They are partly due to the model, where the land based rectifier and the DC reactors are simulated by a constant current source, but partly they have to be handled by overdimensioning of the system. The simulations indicate that it should be technically possible to supply an oil platform with electrical power from land by means of HVDC transmission with small synchronous compensators. Whether this is financially feasible has not been investigated. Neither has it been considered whether the necessary equipment can actually be installed on an oil platform. Recently both ABB and Siemens have presented solutions for HVDC transmission in the lower and medium power range based on voltage source converters based on IGBTs. Fully controllable voltage source HVDC converters have properties that may be better suited than conventional line commutated current source thyristor inverters, to supply weak or passive networks, such as offshore oil installations, with electrical power. But they also have some disadvantages, and a complete technical and financial comparison must be performed in order to decide about any potential project.

The last two decades have witnessed a large increase in capacity in telecommunication systems, thanks to the development of high bandwidth, fiber optic based networks. Nevertheless the continuing growth of Internet data traffic, fuelled by the development of numerous services like on-line commerce, video on demand, large audio/video files downloads, demands for a significant increase in the ability of the network nodes to manage incoming and outcoming data streams effectively and fast. The different functionalities that are needed include add/drop channel multiplexing, routing, signal reshaping and retiming, electrical/optical and optical/electrical conversion. This has stimulated a large effort towards the investigation of technologies for opto-electronic integration at a wafer level, in order to cope with all the required operations, while limiting overall costs. Among the different approaches proposed, one of the most promising is the “Silicon optical bench”, which relies on the well established VLSI technology for the microelectronics part and on planar lightwave circuits (PLCs) made either with silica-on-silicon waveguide technology (low index contrast) of amorphous silicon technology (high index contrast) on the integrated optics side. This thesis presents the development of new techniques and methodologies utilized in photonic device fabrication, which can be used to facilitate integration of temperature sensitive elements. The process is based on low temperature, plasma assisted, thick film deposition. First, a low temperature (300°C) deposition process based on Plasma assisted Chemical Vapour Deposition (PACVD) for the fabrication of silica based Planar Lightwave Circuits (PLC) is developed. The low thermal budget lends itself to monolithic integration with devices fabricated with different technologies. Absorption bands at around the wavelengths 1.48µm and 1.51µm caused by N-H and Si-H bonds within the material, respectively, had previously been thought to be intrinsic to the PACVD deposition method, when using N2O as oxidant gas of SiH4 and the other dopant precursors. The traditional method to eliminate these absorption bands was high temperature (&gt;1000°C) annealing that seriously hinders device integration. An important achievement in this thesis is the improved suppression of these two absorption bands while keeping the whole fabrication temperature below 300°C and also having a high deposition rate. A complete fabrication process for silica planar lightwave circuits was also developed, by optimising the photolithography and etching step. Finally the effect of dopants like Ge and B on the optical properties of the deposited silica glass was investigated, with particular emphasis to the photosensitive properties of the material upon illumination in the near UV. UV trimming is shown to be a versatile method to selectively control polarization birefringence of devices. Transmission dips of above 50dB were achieved in photo-induced gratings in low temperature deposited B-Ge codoped waveguide cores, without the need for hydrogen loading or other sensitisation techniques. The application of a high refractive index like amorphous silicon is addressed for the realization of efficient Bragg reflectors, either as vertical cavity laser mirrors or as dispersive element for planar waveguides used in highly selective co-directional coupler filters. Applications of amorphous silicon as core material for photonic crystal devices are also shown. The investigations carried out in this thesis show that PACVD technology can provide low-loss and UV sensitive material suitable for realizing a variety of low cost integrated devices for future all optical networks. / QC 20101004