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Spatial Diversity and Time-Frequency Orthogonality for Robust Wireless Communications
Zedka, Radim ; Armada, Ana Garcia (oponent) ; Rakús,, Martin (oponent) ; Götthans, Tomáš (vedoucí práce)
This dissertation thesis contains several contributions in the field of robust wireless communications. The first part is focused on developing and analyzing a novel technique of spatial diversity based on the recently discovered concept of space-time line codes (STLCs). Unlike the already known orthogonal STLC, this design is based on a quasi-orthogonal code structure which allows the utilization of four receiver antennas instead of two antennas, which is the limit of the orthogonal STLC for a full rate transmission. The work provides a rigorous theoretical analysis of the diversity gain and asymptotic SNR gain of the new STLC and compares it to the benchmark STLCs. The second part deals with the orthogonal-time-frequency-space (OTFS), a popular multi-carrier waveform showing excellent performance in high-mobility wireless communications. The contribution lies in designing a new OTFS-like system, which - unlike the vast majority of OTFS literature - considers the power-spectral-density (PSD) one of the key design parameters. The novel waveform is named unique-word OTFS (UW-OTFS), because its outer stage is adopted from the popular UW-OFDM. UW-OTFS inherits all of its benefits, including the improved bit-error-ratio (BER) and superb PSD properties. Moreover, the main issue of UW-OFDM, i.e., the multiple-tap equalization, is no longer problematic in the OTFS context. The proposed UW-OTFS is designed to operate in linear time-variant (LTV) fractional-Doppler channels by utilizing a modification of the basis-expansion-model (BEM). Due to this method, both the channel estimation and equalization are performed by the linear minimum-mean-square-error (LMMSE) technique. The proposed system is analyzed both theoretically and numerically (using the Monte Carlo method) and it shows excellent performance in fractional-Doppler channels.
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Thermal management for mission CIMER
Borovička, Matej ; Lazar, Václav (oponent) ; Götthans, Tomáš (vedoucí práce)
This thesis deals with the thermal analysis of the CubeSat, the evaluation and subsequent implementation of the results in the satellite design itself is very important to ensure the proper functioning of all its components. The first part describes thermal analysis issues and proposals for space applications. The second part is devoted to the thermal design of the CIMER nanosatellite, whose mission is to cultivate cyanobacteria in low Earth orbit. Cyanobacteria have very specific requirements in terms of the temperature range in which they can survive. This analysis is therefore very important for the functioning of the entire mission. The thesis describes the creation of a thermal design in the software Systema Thermica, its subsequent analysis and evaluation. Finally, the model is adapted to the conditions required for the survival of cyanobacteria in space.
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Multilevel Converter with Active Gate Drivers for Fault Ride-Through
Klement, Dominik ; Holain, Martin (oponent) ; Götthans, Tomáš (vedoucí práce)
This thesis explores multilevel converters, highlighting their benefits and current/potential future applications. It focuses on the Nested Neutral Point Piloted (NNPP) topology and develops a fault ride-through control algorithm with active capacitor voltage balancing and space vector modulation. The algorithm is validated through simulation. A prototype is designed for experimental validation. The thesis concludes by comparing the proposed fault-tolerant algorithm with existing methods.
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Integration of MHS into microsatellite for qualification mission
Macejko, Jakub ; Götthans, Jakub (oponent) ; Götthans, Tomáš (vedoucí práce)
This diploma thesis investigates the feasibility of a CubeSat demonstration mission to qualify the Miniaturized Heat Switch for space applications. The study assesses various CubeSat configurations from 1U to 3U, focusing on their ability to conduct necessary thermal tests. It establishes that while smaller configurations provide a cost-effective testing platform, larger configurations offer comprehensive testing capabilities.
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Design of 3D printed CubeSat structure for mission KOSTKA
Picka, Marek ; Götthans, Jakub (oponent) ; Götthans, Tomáš (vedoucí práce)
3D print, CubeSat, structure, additive manufacturing, design, random vibration, Quasi static loads, sinusoidal.
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Design of adaptive wireless video and data transmission
Lorenc, Tomáš ; Nykodým, Jiří (oponent) ; Götthans, Tomáš (vedoucí práce)
The aim of this thesis is to build a device that will be able to establish a wireless transmission of a real-time video stream and send the video to a computer where it will be displayed. The device is powered by the NVIDIA Jetson Nano and video is streamed wirelessly through a WiFi interface. In theoretical part described the problem of video transmission and video compression. The used codecs are h264, h265, and VP8. A subjective test to find the minimum acceptable value of video quality was performed. Measurements have been made to find the best codec for real-time video streaming. Measurements were also performed in real conditions. In conclusion, the results of the measurements and the selection of the best codec for real-time video streaming are commented.
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Konstrukce audio výkonového zesilovače ve třídě D
Fiala, Roman ; Götthans, Tomáš (oponent) ; Brančík, Lubomír (vedoucí práce)
Tento semestrální projekt se zabývá popisem výkonových nízkofrekvenčních zesilovačů ve třídě D a konkrétním návrhem zesilovače 2x100W ve třídě D. Navržený zesilovač obsahuje sigma-delta modulátor druhého řádu, u kterého je kvantizace řízena pouze zpožděním prvků modulátoru. Zapojení tedy neobsahuje zdroj hodinového signálu, který obvykle u sigma-delta modulátorů řídí kvantizaci. Součástí tohoto semestrálního projektu je také návrh spínaného zdroje, který slouží k napájení koncového stupně a předzesilovače. K návrhu a ověření některých částí zapojení byl využit program PSpice. Všechna navržená zapojení jsou zkonstruována a jsou změřeny jejich základní parametry.
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Adaptation of digital predistorter to linearize amplifiers using comparator
Jagla, Lukáš ; Ayöz, Suat (oponent) ; Götthans, Tomáš (vedoucí práce)
This master’s thesis presents a development of a new hardware implementing a comparator in the feedback path of DPD systems. A new architecture is proposed and selected features are verified by simulations. Subsequently, the suitable components are selected for high-speed performance and an acquisition module is proposed. A 4-layer PCB is well designed, manufactured, and prepared for further work. Afterwards, an appropriate firmware is developed for signal transmission and data acquisition. The obtained results serves for the evaluation of the proposed architecture and for its future implementation in real DPD systems.
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Automatizovaný měřící systém teploty
Spielmann, Ondřej ; Petržela, Jiří (oponent) ; Götthans, Tomáš (vedoucí práce)
Předmětem této bakalářské práce je seznámení s principy měření meteorologických veličin. Dle získaných poznatků je navržen systém pro automatické měření teploty (případně jiných klimatických veličin) prostřednictvím bezdrátových čidel, která komunikují s řídící jednotkou, ve které jsou získaná data vhodně zpracována a zobrazena. Práce se rovněž zabývá řešením softwarové výbavy systému.
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Multifunkční senzor
Tománek, Jakub ; Götthans, Tomáš (oponent) ; Dřínovský, Jiří (vedoucí práce)
Cílem diplomové práce je seznámení se s možnostmi realizace multifunkčního sensoru určeného pro agrikulturní účely. Práce se v teoretické rovině zabývá principy měření enviromentálních veličin. Následně jsou vybrány sensory jenž jsou schopné měřit příslušné veličiny. V práci jsou rozebrány možnosti bezdrátové komunikace. Pozornost je věnována především komunikačním modulům of výrobce DIGI®. Hlavní část práce popisuje fyzickou realizaci multifunkčního sensoru. Zde je podrobně rozebráno jaké komponenty jsou vybrány na realizaci s přilédnutím k obecným požadavkům na realizaci. Na konci práce je popsán program obsluhující multifunkční sensor.
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