The present society is highly dependant on complex electronics systems, which have a low damage threshold level. Therefore, there is a high risk of partial or total loss of the system’s electronics when they are exposed to a thunderstorm environment. This calls for a deep understanding on the mechanism related to the interaction of lightning generated electromagnetic fields with various large distributed/scattered systems. To accurately represent the interaction of lightning electromagnetic fields with electrical networks, it is necessary to have return stroke models capable to reproduce the electromagnetic field signatures generated by a lightning flash. Several models have been developed in the recent past to study the field-to-wire coupling mechanism. The most popular, simple and accurate among the available models is the Agrawal et al. model. On the other hand, ATP-EMTP is a well-known transient simulation package widely used by power engineers. This package has various built-in line models like Semlyen, Marti and Noda setups. There is a difficulty in applying the Agrawal et al. model with the built-in line models of ATP-EMTP, as the voltage source due to the horizontal component of electric field in Agrawal et al. model is in series with the line impedance and not in between two transmission line segments. Furthermore, when the electromagnetic field is propagating over a finite conducting ground plane, the soil will selectively attenuate the high frequency content of the electromagnetic field; causing a change in the field wave shape. A finite conducting ground will also produce a horizontal field component at the ground level. Several approximations are available in the literature to obtain the horizontal electric field; namely the wave-tilt and the Cooray-Rubinstein approximation. Consequently, it is important to investigate the change on the induced voltage signature when the power line is located over a finitely conducting ground. Additionally, to provide protection from lightning induced transients it is necessary to use Surge Protective Devices (SPDs) capable of diverting the incoming transients and provide protection level necessary to avoid damage in the equipment. However, standard test procedures of the SPDs do not take into account sub-microsecond structure of the transients. Therefore, to provide the required protection level to sensitive equipments connected to the low voltage power network, it is essential to understand the response of SPDs subjected to high current derivative impulses. This thesis is aimed to investigate the research problems as addressed above. Special attention will be given to a new proposed return stroke model, a simple circuit approach for efficient implementation of Agrawal et al. model using ATP-EMTP, the effect of the soil conductivity on the lightning induced overvoltage signatures and the response of surge protective devices subjected to high current derivative impulses.

This thesis discuss on new technique called space time block coding (especially Alamouti's code) which is used to increase capacity and reliability of data transmission over time varying multi-path fading channel. The over all work of the thesis included in the following four chapters. In chapter-1 we are going to cover some theoretical part which is useful to understand thesis work and in chapter-2 we will discuss the comparison between simple space time block code (Alamouti's code) and MRRC (Maximum Ratio Receiver Combining) which is receiver diversity and then in chapter-3 we will see the channel capacity & probability error performance for 2x2 Alamouti code over Rayleigh and Rice fading channel .Finally the conclusion and further work included in chapter-4.

<p>During the last two decades, increase in electricity demand and environmental concern resulted in fast growth of power production from renewable sources. Wind power is one of the most efficient alternatives. Due to rapid development of wind turbine technology and increasing size of wind farms, wind power plays a significant part in the power production mix of Germany, Spain, Denmark and some other countries.</p><p>Wind power has to be built in areas with good wind potential. The best conditions for installation of wind power are, thus, in remote areas free of obstacles, and consequently with low population density. The transmission system in such areas might not be dimensioned to accommodate additional large-scale power plants. Insufficient transmission capacity problem, however, would emerge for any type of new generation, planned in similar conditions, although wind power has some special features that should be considered solving this problem.</p><p>In this thesis the four possibilities are considered. One possibility is to revise the methods for calculation of available transmission capacity. Another solution for large-scale integration of wind power in such areas is to reinforce the network. This alternative however may be expensive and time consuming. Since wind power production depends on the wind speed, the wind farm utilization time is only 2000-4000 hours a year, and power production peaks not necessarily occur during periods with insufficient transmission capacity. Therefore wind energy curtailment may be considered as an alternative for large-scale wind power integration. It is also possible to store excess wind energy during the periods with insufficient transmission capacity. Conventional power plants with possibilities of fast production control (e.g. hydro power plants or gas power plants) may also be employed for this purpose.</p><p>There is a lot of research regarding first two measures, therefore, this thesis provides a review and summarized conclusions from the existing work and further concentrates on development of the methods for estimation of wind energy curtailment and evaluation of wind energy storage possibility in hydro reservoirs.</p><p>Methods similar to probabilistic production cost simulation are developed for estimation of wind energy curtailment. The developed methods are applicable to discrete variables (measurements) and also generalized for continuous variables with known distribution.</p><p>For evaluation of wind energy storage possibility the optimization problem is formulated, the objective of this evaluation is to minimize the costs for power production under consideration of the future water value. The developed method allows us to analyze previous years of operation of the power system (e.g. dry, wet and normal year) and evaluate physical possibilities for wind energy storage. The developed methods are than tested for Swedish power system and the results are also summarized in this thesis.</p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p> / QC 20100607

Organic electronics has evolved into a well-established research field thanks to major progresses in material sciences during recent decades. More attention was paid to this research field when “the discovery and development of conductive polymers” was awarded the Nobel Prize in Chemistry in 2000. Electronic devices that rely on tailor-made material functionalities, the ability of solution processing and low-cost manufacturing on flexible substrates by traditional printing techniques are among the key features in organic electronics. The common theme while exploring organic electronics, and the focus of this thesis, is that (semi-)conducting polymers serve as active materials to define the principle of operation in devices. This thesis reviews two kinds of organic electronic devices. The first part describes electrochemical devices based on conducting polymers. Active matrix addressed displays that are printed on flexible substrates have been obtained by arranging electrochemical smart pixels, based on the combination of electrochemical transistors and electrochromic display cells, into cross-point matrices. The resulting polymer-based active-matrix displays are operated at low voltages and the same active material is used in the electrochemical transistors as well as in the electrochromic display cells, simply by employing the opto-electronic properties of the material. In addition to this first part, a switchable optical polarizer based on electrochromism in a stretch-aligned conducting polymer is described. The second part reports switchable charge traps in polymer diodes. Here, a device based on a solid-state blend of a conjugated polymer and a photochromic molecule has been demonstrated. The solid state blend, sandwiched between two electrodes, provide a polymer diode that allows reversible current modulation between two different charge transport mechanisms via externally triggered switching of the charge trap density.

<p>This thesis discusses design of narrowband low noise amplifiers for multi¬standard applications. The target of this work is to design a low noise ampli¬fier(LNA) for DCS1800 and Bluetooth standard frequency bands. Various designs for narrowband multi-standard LNAs have been studied and a new design for tunable multi-standard LNA has been presented and designed using accumulation mode MOS varactors.</p><p>As this design includes on-chip spiral inductors, the design, modelling and layout of on-chip inductors have been discussed briefly. The tool used for this purpose is ASITIC.</p><p>Also ESD protection techniques for RF circuits and their effect on LNA per¬formance has been discussed.</p><p>Finally fully differential LNA has been designed in O.35um AMS thick metal CMOS process using Cadence SpectreRF. The design also includes ESD pro¬tection at the input of LNA.</p>

<p>This thesis introduces a coding scheme for very low bitrate video coding through the aid of principal component analysis. Principal information of the facial mimic for a person can be extracted and stored in an Eigenspace. Entire video frames of this persons face can then be compressed with the Eigenspace to only a few projection coefficients. Principal component video coding encodes entire frames at once and increased frame size does not increase the necessary bitrate for encoding, as standard coding schemes do. This enables video communication with high frame rate, spatial resolution and visual quality at very low bitrates. No standard video coding technique provides these four features at the same time.</p><p>Theoretical bounds for using principal components to encode facial video sequences are presented. Two different theoretical bounds are derived. One that describes the minimal distortion when a certain number of Eigenimages are used and one that describes the minimum distortion when a minimum number of bits are used.</p><p>We investigate how the reconstruction quality for the coding scheme is affected when the Eigenspace, mean image and coefficients are compressed to enable efficient transmission. The Eigenspace and mean image are compressed through JPEG-compression while the while the coefficients are quantized. We show that high compression ratios can be used almost without any decrease in reconstruction quality for the coding scheme.</p><p>Different ways of re-using the Eigenspace for a person extracted from one video sequence to encode other video sequences are examined. The most important factor is the positioning of the facial features in the video frames.</p><p>Through a user test we find that it is extremely important to consider secondary workloads and how users make use of video when experimental setups are designed.</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.

This thesis presents technological advancements in microfluidics. The overall goals of the work are to develop new miniaturized tests for point-of-care diagnostics and robust super-lubricating surfaces for friction reduction. To achieve these goals, novel materials, surfaces and manufacturing methods in microfluidics have been developed. Point-of-care diagnostic tests are portable miniaturized instruments that downscale and automate medical tests previously performed in the central laboratories of hospitals. The instruments are used in the doctor’s office, in the emergency room or at home as self-tests. By bringing the analysis closer to the patient, the likelihood of an accurate diagnosis, or a quick therapy adjustment is increased. Already today, there are point-of-care tests available on the market, for example blood glucose tests, rapid streptococcus tests and pregnancy tests. However, for more advanced diagnostic tests, such as DNA-tests or antibody analysis, integration of microfluidic functions for mass transport and sample preparation is required. The problem is that the polymer materials used in academic development are not always suited for prototyping microfluidic components for sensitive biosensors. Despite the enormous work that has gone into the field, very few technical solutions have been implemented commercially. The first part of the work deals with the development of prototype point of-care tests. The research has focused on two major areas: developing new manufacturing methods to leverage the performance of existing materials and developing a novel polymer material platform, adapted for the extreme demands on surfaces and materials in miniaturized laboratories. The novel manufacturing methods allow complex 3D channel networks and the integration of materials with different surface properties. The novel material platform is based on a novel off-stoichiometry formulation of thiol-enes (OSTE) and has very attractive material and manufacturing properties from a lab-on-chip perspective, such as, chemically stable surfaces, low absorption of small molecules, facile and inexpensive manufacturing process and a biocompatible bonding method. As the OSTE-platform can mirror many of the properties of commercially used polymers, while at the same time having an inexpensive and facile manufacturing method, it has potential to bridge the gap between research and commercial production. Friction in liquid flows is a critical limiting factor in microfluidics, where friction is the dominant force, but also in marine applications where frictional losses are responsible for a large part of the total energy consumption of sea vessels. Microstructured surfaces can drastically reduce the frictional losses by trapping a layer of air bubbles on the surface that can act as an air bearing for the liquid flow. The problem is that these trapped air bubbles collapse at the liquid pressures encountered in practical applications. The last part of the thesis is devoted to the development of novel low fluidfriction surfaces with increased robustness but also with active control of the surface friction. The results show that the novel surfaces can resist up to three times higher liquid pressure than previous designs, while keeping the same friction reducing capacity. The novel designs represent the first step towards practical implementation of micro-structured surfaces for friction reduction. / <p>QC 20110907</p>

ORMOCERR®s are organic-inorganic hybrid polymers. Since their material properties can be tailored precisely during synthesis, they are suitable for a wide range of applications in dielectric and optical microelectronics. This thesis reports on process development of ORMOCERR®s for Sequentially Build-Up (SBU) test vehicles, suitable for both electrical and optical interconnect. Furthermore, this work includes materials characterization, such as refractive index studies (system B59:V32), optical loss measurements (systems B59:V32 and B59:B66), and surface characterization through contact angle measurement and surface energy estimation (systems B59:V32 and B59:B66). Process development for a high-frequency test vehicle was performed applying a newly developed dielectric material of the ORMOCER® class. Dielectric layers in a total thickness of 80 μm were build-up on a common FR4 substrate, applying photolithographic processes and moderate process temperatures of below 433 K. The loss tangent and the permittivity of the material were measured to be 0.024 (loss tangent) and 3.05 (permittivity) over the entire frequency range 10 GHz to 40 GHz. The compatibility of the material to standard processes of the PCB industry was proven. Furthermore, a possibility for cost reduction in high-frequency MCM applications was shown, through the possibility of using low-cost substrates. The concept of a “flexible manufacture approach” for large-area panel optical backplane interconnects was introduced. Here, a 101.6 mm x 101.6 mm photolithographic mask is to be stepped-out over a large-area panel substrate (up to 609.6 mm x 609.6 mm). The goal is to be able to create a large amount of continuous and unique waveguide patterns over the whole area with a small portfolio of masks, thus being able to minimize excess costs. In practice continuous waveguide patterns were created over an area of 204.8 mm x 204.8 mm on a large-are panel (609.6 mm x 609.6 mm), using a large-are mask aligner and a 101.6 mm x 101.6 mm waveguide mask. The optical loss of the waveguides was measured to be 0.6 dB/cm (B59:V32 material system, λ =850 nm). In connection to the large-area panel project a re-evaluation on the optical power budget needed for high bit rate optical interconnects was performed. This work was mainly based on literature surveys of optical waveguide materials, planar optical amplifiers, light coupling structures, and planar light-routing structures. It was shown that optical amplification is necessary at certain places on realistically routed optical backplanes to boost the optical signal. Therefore, the concept of a flip-chip mountable optical amplifier (FOWA) device, based on planar optical waveguide amplifiers and Semiconductor Optical Amplifiers, was developed. The device’s design allows an independent manufacturing to the rest of the board and a mounting at key-positions using standard pick and place technology. Additionally, it was observed that most of the amplifier research is focused on the wavelength of 1310 nm and 1550 nm, whereas optical backplane applications are targeting the 830 nm range. During SBU processing of waveguide structures was discovered a de-wetting phenomenon of B59 resin on a cured B59:B66 and B59:V32 surface, respectively. Good wetting behavior could be achieved by adding small amounts of B66 or V32, respectively, to the B59. Surface tension estimations on various compositions of the systems B59:B66 and B59:V32 could not directly be correlated to the de-wetting phenomenon. Furthermore, the optical loss properties of B59 were only affected to a minor degree by adding B66 or V32. The process route proposed is an efficient alternative to processes including surface activations steps, thus opening possibilities for large-area processing in PCB industry, where surface activation steps, such as plasma activation or silanization, are not available. The process development, materials characterization, and reviews presented provide a basis for further research on processes for high-performance electro/optical backplane interconnects with focus on Large-Area Panel processing.

Fibre Bragg gratings (FBGs) are key components for a vast number of applications in optical communication systems, microwave photonics systems, and optical sensors, etc. The main topic of this thesis is fibre Bragg grating fabrication and applications in direct microwave optical filtering, high speed switching and switchable dual-wavelength fibre lasers. First, a brief overview is given about the photosensitivity in optical fibre, basic FBG fabrication techniques, the popular coupled-mode theory for describing fundamental characteristics of FBGs and the Transfer Matrix method for the numerical simulations of complex-structured FBGs. An advanced FBG fabrication system based on the technique of multiple printing in fibre (with a continuous-wave source) has been used to write complex FBGs incorporating phase shifts, apodization and chirp.      A single double-peaked superimposed grating working in reflection can be employed as a direct optical filter for millimetre-wave signals. Bit error rate measurements confirmed that the filter exhibited nearly on-off behaviour in the passband with a 3-dB bandwidth of 2 GHz for a central frequency of 20 GHz, as expected from the optical spectrum reflection. The presented technique can be used in radio-over-fibre systems or simultaneous up-conversion of ultra-wide band signals and filtering. This thesis focused mostly on the research of two 4-cm long Hamming-apodized gratings written in side-hole fibres with internal electrodes. The temperature dependence measurements showed that the birefringence of the component increased with the temperature. Dynamic measurement has shown nanosecond full off-on and on-off switching. During the electrical pulse action, the grating wavelength was blue-shifted for the x-polarization and red-shifted for the y-polarization due to the mechanical stress. Both peaks subsequently experienced a red-shift due to the relaxation of mechanical stress and the increasing core temperature transferred from the metal in many microseconds. All the wavelength shifts of the two polarizations depend quadratically on the electrical pulse voltage and linearly on the pulse duration. Numerical simulations gave accurate description of the experimental results and were useful to understand the physics behind the birefringence switching. Finally, two switchable dual-wavelength erbium-doped fibre lasers based on FBG feedback were proposed. In one method, an overlapping cavity for the two lasing wavelengths and hybrid gain medium in the fibre laser were introduced. Dual-wavelength switching was achieved by controlling the Raman pump power. The other method employed an injection technique and the dual-wavelength switching was controlled by the power of the injection laser. The switching time was measured to be ~50 ms. Detailed characteristics of the dual-wavelength switching in the two fibre lasers were experimentally studied and corresponding principles were physically explained. / QC 20100922