05 Fakultät Informatik, Elektrotechnik und Informationstechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6
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Item Open Access Radiation mitigation techniques for EIVE satellite mission payload computer(2022) Bischof, TobiasDie Satellitenmission ’Exploratory In-orbit Verification of an E/W-band link’ (EIVE) demonstriert die breitbandige Datenübertragung von der niedrigen Erdumlaufbahn zur Erde mit Datenraten von bis zu 15 Gbits−1.Umden korrekten Betrieb des EIVE-Satelliten sicherzustellen und die Strahlungseinwirkungen auf die Schaltung von EIVE zu reduzieren, sind Strahlungsminderungstechniken für den Nutzlastcomputer erforderlich. Daher untersucht diese Arbeit die Strahlungsminderungstechniken, Mechanismen für den Schutz des FPGA-Konfigurationsspeichers und implementiert robuste Kodierungsmechanismen der E/W-Band-Validierungsdateien. Die Untersuchungen und die implementierten Ansätze stehen dabei im Einklang mit den Leistungsbeschränkungen der Mission.Item Open Access Digital self-interference cancellation using FPGA for in-band full-duplex radios(2023) Roge, Swapnil SunilConventionally, the transmission and the reception of signals in a particular wireless communication system is performed using the half-duplex method, wherein the transmitter and the receiver signals are either time-multiplexed or frequency-multiplexed. However, in case of an in-band full-duplex system, the bidirectional communication of signals is performed simultaneously in the same frequency band, which improves the spectral efficiency of these systems by a factor of two as compared to the traditional half-duplex systems. Therefore, the in-band full-duplex communication systems can double the data rate provided by the half-duplex communication systems, thereby making the former a matter of interest across the wireless research community. However, the in-band full-duplex systems have theirownset of disadvantages. The major challenge is the self-interference imposed by the high-power transmitter signal on the incoming low-power receiver signal, which further degrades the latter and negatively impacts its estimation. Out of the various methodologies to mitigate the self-interference from the receiver signal, this work focuses on the digital self-interference cancellation techniques. In this thesis, the effects of the self-interference signal on the receiver signal are examined. Furthermore, the different digital self-interference cancellation methods employed for suppressing the self-interference are comparatively analysed. Finally, the field-programmable gate array based implementation of the various digital self-interference cancellation algorithms and their respective performance results are presented as well.Item Open Access Novel characterization techniques for the study of the dynamic behavior of silicon carbide power MOSFETs(2022) Salcines, Cristino; Kallfass, Ingmar (Prof. Dr.-Ing.)This dissertation provides insight into the dynamic behavior of SiC power MOSFETs from their inherent static IV and CV characteristics. While conventional dynamic measurements extracted from a DPT or a similar dynamic test-bench yield accurate quantitative data, the static IV and CV characteristics of a power semiconductor device offer more qualitative information to delve into the root mechanisms responsible for its dynamic behavior. Conventional characterization techniques are limited to power levels way below those which the power device withstands in the application. As a result, the static IV and CV characteristics attained by available measurement solutions are reduced to a limited scope of bias conditions insufficient to infer information about the dynamic behavior of the power device. This work tackles this gap and proposes novel measurement techniques that enable the characterization of the static IV and CV characteristics of SiC power MOSFETs at the full range of bias conditions the power device goes through in the application. Iso-thermal IV characteristics of a commercially available SiC power MOSFET are measured up to 40 kW power (instantaneous 50 A and 800 V) at junction temperatures ranging from 25°C to 175 °C. The CV characteristics are mapped at drain-source and gate-source bias combinations of VDS = 0 - 40 V and VGS = 0 - 20 V, respectively, at junction temperatures ranging from 25°C to 150 °C. The results of these measurements reveal unique insights into the electrical characteristics of SiC power MOSFETs which impact their performance in the application and explain unclear phenomena observed in their dynamic behavior. On the one hand, the intrinsic capacitances of the SiC power MOSFET extend their non-linearity, function of both VGS and VDS, to the saturation region of the power device. Moreover, they are also affected by the junction temperature of the power device. The impact of these in the voltage commutation speed of the device under different switching conditions is thoroughly analyzed in the thesis. On the other hand, the IV characteristics of the SiC power MOSFET reveal the existence of short channel effects that drastically affect the transconductance of the power device in its high voltage saturation region. Furthermore, the measurements show a positive temperature coefficient of the drain current in the high voltage saturation region of the SiC power device, attributed to the density of trap energy states in the SiC/SiO2 interface. These effects effectively lower the plateau voltage of the device and lead to faster current commutation speeds in the application than those expected from the datasheet values. The insights revealed by the proposed characterization techniques are intended to help fine-tune semiconductor technology processes and improve the accuracy of simulation models to achieve a higher grade of optimization in the design of future SiC-based energy conversion circuits.Item Open Access Design of frequency-converting monolithic integrated circuits for millimeter-wave applications(2022) Grötsch, Christopher; Kallfass, Ingmar (Prof. Dr.-Ing.)This thesis focuses on how to efficiently utilize the low terahertz spectrum in the frequency range from 220 to 325 GHz, also called H-band. This work presents an introduction on several techniques necessary for designing frequency-converting monolithic millimeter-wave integrated circuits for this frequency range. Six different frequency-converter MMICs in a 35 nm gate-length InGaAs mHEMT technology are presented: a nonlinear resistance up- and down-converter, a dual-gate up and down-converter, a gate-pumped transconductance up-converter and a half Gilbert cell up-converter. Each design is explained in detail, their advantages and their disadvantages are evaluated. Three examples will be given where a selection of the frequency-converter architectures are integrated with other functional stages like frequency multipliers and amplifiers to form a millimeter-wave transceiver: a highly linear FMCW radar receiver with a 50 GHz bandwidth, a heterodyne communication receiver facilitating multi-channel transmissions with carrier aggregation at W-band and a homodyne communication receiver with an integrated antenna for low-cost assembly on a PCB. Thereby, this thesis provides insight into the design considerations of terahertz frequency converters, the trade-off of different circuit architectures and topologies for certain applications, the obstacles that can occur during their development and approaches to overcome them.Item Open Access Sensorfusion auf Basis maschinellen Lernens zur Bestimmung der Sperrschichttemperatur(2024) Kuderna Melgar, DiegoDie genaue Bestimmung der Sperrschichttemperatur spielt eine elementare Rolle bei der Optimierung der Leistungsfähigkeiten sowie der Zuverlässigkeit von SiC (Silicon Carbide)-Leistungsmodulen. Im Rahmen der indirekten Bestimmung der Sperrschichttemperatur lassen sich Temperature Sensitive Electrical Parameters (TSEPs) einsetzen, die jedoch neben der Sperrschichttemperatur weitere Abhängigkeiten von elektrischen Größen aufweisen. Dies kann zu einer ungenauen Schätzung der Sperrschichttemperatur führen, weshalb diese Bestimmung robuster gestaltet werden muss. Ein Ansatz, um dies zu erreichen, stellt die Kombination mehrerer TSEPs dar, die im Anschluss mithilfe einer KI auf einem Mikrocontroller verarbeitet werden. In dieser Arbeit werden zwei unterschiedliche Ansätze aufgezeigt, um anhand von maschinellen Lernens die Sperrschichttemperatur eines Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) auf Basis von TSEPs zu bestimmen. Hierzu werden die Werkzeuge NanoEdgeAI Studio sowie X-CUBE-AI eingesetzt, um die entwickelten Modelle auf einem STM32 Mikrocontroller zu implementieren. Ein Vergleich beider Ansätze zeigt, dass NanoEdgeAI Studio Modelle mit effizienterer Nutzung der Ressourcen des Mikrocontrollers ermöglicht. Im Gegensatz dazu erreichen in Python entwickelte Modelle in Kombination mit X-CUBE-AI ohne Quantisierung präzisere Schätzungen bei größerem Speicherbedarf. Im Kontext der Arbeit werden diverse Untersuchungen durchgeführt, um die Schätzgenauigkeit der betrachteten Modelle zu maximieren. Dazu gehören Ensemblebildung und Trainingsprozesse mit unterschiedlich großen Datensätzen sowie die Variation der Anzahl der Eingabesignale. So lässt sich zeigen, dass sich durch Bildung von Ensembles der R-Squared-Wert bei gleichzeitiger Reduktion des maximalen Fehlers erhöhen lässt. Durch Vergrößerung des Datensatzes lässt sich dieser Wert ebenfalls anheben und eine Steigerung durch die Kombination von TSEPs ist beobachtbar. Die realisierten Algorithmen erzielen unabhängig von der Qualität der gemessenen Signale höhere R-Squared-Werte als der traditionelle Ansatz, der lediglich einen elektrischen Parameter für die Schätzung der Sperrschichttemperatur einsetzt. Dieser beträgt 97,9% und der maximale Fehler weist einen Wert von 14K auf. So lässt sich durch die Kombination sämtlicher TSEPs ein Random Forest in NanoEdgeAI Studio entwickeln, der einen R-Squared-Wert von 99,03% erzielt, was einem Zuwachs von 1,13 Prozentpunkten entspricht. Überdies bemisst der maximale Fehler 8K, was 6K unter dem maximalen Fehlers des konventionellen Ansatzes liegt. Zusätzlich ermöglicht dieses Vorgehen die Bestimmung weiterer Parameter, exemplarisch lässt sich der Laststrom nennen.Item Open Access A comparison of system architectures for wireless links in the terahertz band(2022) Dan, Iulia; Kallfass, Ingmar (Prof. Dr.-Ing.)This thesis shows an in-depth analysis of two system architecures used for future terahertz communication systems. For each architecture wireless data transmissions are carried out based on analog frontend devices that use that particular architecuture. The performance of the links is compared and the structure of the wireless links is described in detail and analyzed.Item Open Access Search algorithm for the ground station antenna of the EIVE satellite(2023) Erdogan, Mustafa EfeSatellite technologies have rapidly become integral to modern life, used for broadcasting, navigation, communication, and Earth observation. As technology advances, satellites generate increasingly large volumes of data, presenting hardware challenges in terms of data storage and transmission due to limited power sources. To meet the escalating demand for high-capacity channels with high data rates, the EIVE project was initiated to explore the feasibility of using E-band frequencies (71-76 GHz) for satellite communication. EIVE, led by the University of Stuttgart in collaboration with various partners, aims to test data transfer capabilities in this uncharted frequency range. A key challenge is the establishment of a communication link between a ground station antenna and the LEO satellite in the EIVE project. This task is compounded by the ground station’s Cassegrain antenna with a narrow HPBW of 0.23° and a low achieved scanning area because of the LEO. To address these challenges, this research thesis introduces a CONSCAN based search algorithm, which expands the antenna’s scanning area by executing conical patterns around the satellite’s estimated trajectory. By using quaternion rotations and the Orekit library for trajectory estimation, this algorithm significantly enhances the search capabilities, increasing the scanning area in the sky. Furthermore, the research highlights the importance of continuous signal acquisition from the satellite for the planned data transfers. To tackle this issue, the groundwork for a tracking algorithm based on theMMTmethod is introduced to provide precise measurements of the satellite’s position, combining the MMT method with Kalman filters and GPS based methods. This novel method promises the improvement of the accuracy and stability of the system.Item Open Access Entwicklung einer Methodik zur Bestimmung der Schaltverluste von diskreten 400V-GaN-Halbbrücken(2023) Bauer, Nikolas; Kallfass, Ingmar (Prof. Dr.-Ing.)Basierend auf aktuellen und zukünftigen Entwicklungsprämissen miniaturisierter automobiler Leistungselektronik wird in dieser Thesis die diskret verortete 400 Volt Gallium-Nitrid Halbbrücke als Kernkomponente einer fahrzeuggebundenen Hochvoltspeicher-Ladertopologie mit 3,7 Kilowatt Ladeleistung betrachtet. Die nachfolgende Methodikentwicklung zur Quantifizierung zeittransienten Schaltverhaltens und damit insbesondere generierter Halbbrückenverlustleistungen diskutiert die Vorteile der in dieser Arbeit entwickelten VERILOG Halbleitersimulation auf Basis verfügbarer ASM-HEMT Modelle der Compact Model Coalition gegenüber der Genauigkeit konventioneller SPICE-Simulation. Simulative Durchführungen dieser Arbeit berücksichtigen notwendige Betriebsparameter der Halbbrücke, insbesondere Totzeiten sowie deren Detektion per zum Patent angemeldeter Auswertelogik, und erlauben darüber hinaus in VERILOG die globale Schaltzellenoptimierung. Simulative Ergebnisse werden anhand einer dedizierten Power Factor Correction Stufe zeittransient und kalorimetrisch validiert. Die vorgestellten Simulationsmethodiken erlauben somit zukünftig die vollständig virtualisierte Hardwareauslegung von Leistungselektronik hinsichtlich Zeit- und Verlustverhalten.Item Open Access Efficient joint broadband radar and communication for airborne SAR imaging with small platforms(2024) Johannes, Winfried; Kallfass, Ingmar (Prof. Dr.-Ing.)Item Open Access Power semiconductor loss characterization and advanced thermal management for high power density AC/DC battery chargers(2024) Weimer, Julian; Kallfass, Ingmar (Prof. Dr.-Ing.)This dissertation investigates the challenges related to achieving higher power density in AC/DC battery chargers, particularly for compact electric vehicles such as e-bikes. The growing demand for battery-powered devices has driven the expansion of the global battery charger market, reaching a valuation of $24.5 billion in 2022. To support the transition to sustainable electrified transportation, it is essential to develop energy and resource-efficient designs, requiring power electronics capable of handling increased power density with enhanced efficiency and thermal management. Gallium nitride semiconductors have gained prominence in the battery charger domain due to their superior switching efficiency. This technology promotes the shift towards elevated switching frequencies, resulting in smaller passive components in power electronics. However, it also exposes significant electrical and thermal limitations that must be addressed to further enhance power density. Despite the minimal soft-switching loss energy of modern wide bandgap devices, substantial total losses emerge at multi-kilohertz operation. Furthermore, there is no standardized method for accurate characterization. Consequently, a consistent measurement approach is needed to optimize the multi-domain challenge within virtual prototyping based on precise loss models. Additionally, innovative thermal management concepts must be devised to tackle the constrained cooling capacity of increasingly smaller plastic housings, preventing power density limitations due to surface temperature standards. The research objectives of this work encompass the development of a rapid, non-invasive calorimetric characterization method for accurate soft-switching loss measurement, utilizing the results to design and construct a high-density mobile battery charger hardware prototype, proposing a novel thermal topology optimization concept for uniform charger surface temperature, and advancing thermal management to incorporate heat storage for achieving effective power density beyond the constraints imposed by continuous output power. The proposed concepts are validated through experiments and simulations, offering a comprehensive understanding of modern battery charger limitations and suggesting strategies to overcome them. This dissertation presents a high-density, two-stage battery charger prototype for compact electric vehicles, achieving a power density of 1.1 kW/dm³ with a system efficiency of 94.2 %, enabled by calorimetric semiconductor selection and loss modeling. Topology optimization employing accurate loss models can lead to a substantial improvement in system power density, up to 11.5 %, while limiting junction temperature increases. The proposed thermal management concept, utilizing heat storage, attained a 40 % higher power density for a 50 Wh battery by fully utilizing both static and dynamic cooling capabilities of the charger.