05 Fakultät Informatik, Elektrotechnik und Informationstechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6

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Institute: search.filters.UBSInstitut.Institut für Robuste LeistungshalbleitersystemeAuthor: search.filters.author.Wiewel, Florian

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    FPGA implementation of an energy-efficient real-time image compression algorithm for the EIVE satellite mission
    (2021) Wiewel, Florian
    In this thesis three commonly used image compression algorithms are analyzed in terms of computational complexity, rate-distortion performance and execution time in order to find the most suitable basis for the implementation of an energy-efficient and real time image compression algorithm for the EIVE satellite mission. The selected algorithm is than modified to reduce its complexity while keeping its performance at a comparable level to the base algorithm. Afterwards the algorithm is implemented in the programmable logic part of a Xilinx Zynq UltraScale+ MPSoC device. Finally, the performance of the algorithm implemented on hardware is determined and compared to the performance of an implementation using a high-level scripting language and the performance of its base algorithm.
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    Digital pre-distortion of broadband communication links using open-loop architecture
    (2021) Wiewel, Florian
    The ever-increasing demand for higher data rates and lower latency in wireless communications ultimately forces the developers of the underlying systems to use broadband links with higher order modulation formats to meet this demand. The use of these modulation formats results in strict linearity requirements on the system. On top of that power, efficiency is also an important aspect, since it has an impact on the operational costs and ecological compatibility. In a typical macrocell for modern wireless communication systems, the power amplifier (PA) of the base station consumes about 60% of the overall power and it is also the PA, which typically exhibits the strongest nonlinear transfer characteristic in the system. Unfortunately, power efficiency and linearity represent conflicting requirements in PA design. As a result, a compromise between these two requirements has to be made. Usually, the PA is designed for high power efficiency and with moderate nonlinear transfer characteristics. To compensate for the nonlinearity in the PA a technique called digital pre-distortion (DPD) is applied, which estimates the nonlinearity in the PAs transfer characteristic and applies the corresponding inverse transfer function to the complex baseband input signal of the PA in the digital domain. In contrast to many of the DPD experiments found in literature, which are applied to signals with bandwidths in the range of tens of megahertz, the targeted linearization bandwidth in this work is 5 GHz. For this purpose an open-loop DPD architecture based on the Volterra theory of nonlinear systems specifically the p-th order inverse has been implemented in software and applied to different amplifiers including a waveguide E-band transmitter operating around 73 GHz. Up to a signal bandwidth of around 1 GHz significant improvements in terms of signal quality could be observed in the conducted experiments. For signals with higher bandwidths problems with signal integrity caused the DPD to fail. Finally, the various problems are analyzed and potential improvements for increasing the DPD performance for wideband signals are suggested.