One of ABB Power Systems´s business areas is HVDC (High Voltage Direct Current) technology. HVDC is used for transmissions for both short and long distances. One of Power Systems’s products is called HVDC Light. HVDC Light is a relatively new technology for power transmission, but have before only been used for motor drives applications. The technology is based on VSC (Voltage Source Converter) that uses a technique called PWM (Pulse Width Modulation). There are a lot of PWM patterns that have been examined, but not in the field of power transmission where ABB Power Systems is working. The different PWM patterns can be used for reducing switching losses or harmonics, that can cause the need of external filters to decrease or increase. The purpose of this report is to give a general picture of the system that generates the PWM patterns. The report describes some main components in the system. T he thesis also present amplitude spectrum from various PWM patterns - generated by signals that have been pulse width modulated with a triangle- shaped wave. By showing the frequency-content, the decisions are eased for the engineers and technicians that are working with this kind of questions. An analysis of different PWM patterns have been done. The kind of reference waves that generate the PWM patterns are called Dead Band PWM and Modified SPWM. Comparisons have been done for Dead Band PWM, between harmonics and the width of Dead Band. Comparisons have been done for Modified SPWM, between: 1. fundamental frequency and modulation index. 2. different Modified SPWM and their harmonics.

Today radars are used to measure the distance to almost anything. It is used to determine the position of airplanes as well as the level of an oiltank. To achieve high precision in level gauging radars high quality components are demanded. This makes them expensive. In this project we evaluate the possibility to use relatively cheap components, used in radio communication, to measure distances with an OFDM-modulated signal. The components are cheap due to large production volumes rather than low performance. To do this we started with working out the theory needed for length estimation. At our disposal we had the SDR SFF Development Platform from Lyrtech. A simulation model of the platform was built in MatLab. This model was used to verify the theory developed. Finally our algorithms was implemented on the development platform. Both simulations and real life measurements show that OFDM can be used to measure distances. Even though the hardware used in this project is not dedicated for this application we managed to perform measurements with good accuracy at short range. We believe that with more suitable hardware OFDM-radars will be able to compete with todays high end level gauging radars at all ranges. / Nu för tiden används radar för att mäta avstånd i en rad olika sammanhang. Det används till allt från att bestämma positionen på flygplan till att mäta nivån i oljetankar. För att uppnå den höga precision som krävs vid nivåmätning ställs höga krav på de ingående komponenterna. Detta gör att radarn blir dyr. I detta examensarbete utvärderar vi möjligheten att använda relativt billiga komponenter, som används inom radiokommunikation, för att mäta avstånd med hjälp av en OFDM-modulerad signal. Dessa komponenter är billiga till följd av stora tillverkningsvolymer, inte för att de är dåliga. Till att börja med tog vi fram den teori som behövdes för att skatta avstånd. Till vårt förfogande hade vi Lyrtechs SDR SFF Developmemt Platform. En simuleringsmodell av platformen gjordes i MatLab vilken användes för att verifiera teorin. Slutligen implementerades algoritmerna på utvecklingsplattformen. Både simuleringar och riktiga mätningar visar att OFDM kan användas för att mäta avstånd. Trots att hårdvaran som användts under examensarbetet inte är anpassad för avståndsmätning blev mätresultaten goda för korta avstånd. Vi är övertygade om att med en, för ändamålet, mer anpassad hårdvara kommer en OFDM-radar upppnå samma precision som dagens högpresterande nivåmätareäven för längre avstånd.

When working with oceans in the visual effects industry, it is not always very practical or even possible to use real live footage, especially if extreme weather conditions are required. A common scenario is computer generated objects crashing into an ocean generating splashes and foam that should stick to and integrate well with the real ocean surface. Making a shot like that look realistic is very difficult, this is where a fully computer generated ocean surface comes in handy. Creating high resolution computer generated sequences of an ocean surface with interacting objects is difficult using today’s available commercial 3D packages. I have therefore implemented a VFX ocean toolkit, which is a system built for generating the ocean surface, Kelvin wakes and interaction with objects. The ocean toolkit was built with the artist in mind and the need for real time preview to produce results quick and easy in order for the system to remain cost effective. The ocean toolkit is tightly integrated directly into the procedural 3D animation package Houdini1 as several plug-ins and shaders that can be combined to create numerous ocean surface effects.

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Extracting the Electric Network Frequency (ENF) fluctuations from an audio recording and comparing it to a reference database is a new technology intended to perform forensic digital audio authentication. The objective of this thesis is to implement and design a range of programs and algorithms for capturing and extracting ENF signals. The developed C-program combined with a probe can be used to build the reference database. Our implementation of the Short-Time Fourier Transform method is intended for the ENF extraction of longer signals while our novel proposed use of the Autoregressive parametric method and our implementation of the zero-crossing approach tackle the case of shorter recordings. A Graphical User Interface (GUI) was developed to facilitate the process of extracting the ENF fluctuations. The whole process is tested and evaluated for various scenarios ranging from long to short recordings.

This thesis describing basic concepts and parts of OFDM modulator, showing their implementation in Matlab. It’s focused on how to use USRP with Matlab to create fully functional OFDM modulator.

In this thesis there is a design of universal time-variant convolution FIR processor. Proposed algorithm is ready to process long signals with reduced process delay. Furthermore, there are proposed methods for smooth crossfade between different impulse responses. Algorithm is implemented in Matlab environment and later as a VST plugin.

The aim of this thesis is to study the possibilities of spectrum calculations, as well as data transfer via USB 3.0 and data saving to a DDR3 memory via FPGA. The focus is also on design and realization of a spectral analyzer with a record of samples to DDR memory expnaded by a narrowband converter using gate arrays. The work is divided into two sections, the first one dealing with the theoretical background. The second part denotes the realization of the design. The result of this work is a signal analyzer in a FPGA controlled from a computer application via the USB 3.0 interface.

Damping and natural frequency of a vibrating body or a system is not easy to estimate during the design phase of~project. If the body is submerged in water, estimating becomes even more complicated. This~work focuses on experimental determination of the liquid influence on an oscillating body. The~presented modal analysis was executed on two bodies when being surrounded by air, but~also when gradually and fully submerged in water using two reservoirs with different dimensions. The collected data was analyzed with a suggested hybrid method, which determined the damping ratio and the natural frequency. Added mass was calculated employing the Ansys software. Part of the presented work focuses on the selection of a suitable time window for the Fourier transform.

This thesis is a part of the k-Wave project, which is a toolbox for the simulation and reconstruction of acoustic wave felds and one of its main contributions is the planning of focused ultrasound surgeries (HIFU). One simulation can take tens of hours and about 60% of the simulation time is taken by the calculation of the 3D Fast Fourier transforms. Up until now the 3D FFT has been calculated purely by the FFTW library and its 1D decomposition, whose major limitation is the maximum number of employable cores. Therefore we introduce a new approach, called the 2D hybrid decomposition of the 3D FFT (HybridFFT), where we combine both MPI processes and OpenMP threads to reach as best performance as possible. On a low number of cores, on the order of a few hundreds, we are about as fast or slightly faster than FFTW and pure MPI 2D decomposition libraries (PFFT and P3DFFT). One of the best results was achieved on a 512^3FFT using 512 cores, where our hybrid version run 31ms, FFTW run 39ms and PFFT run 44ms. The most significant performance advantage should be seen when employing around 8-16 thousand cores, however we haven't had an access to a machine with such resources. Almost a linear scalability has been proven for up to 2048 employed cores.