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Item type:Publication, Access status: with files , Development of data-efficient machine learning approaches for the modeling and design in electromagnetic compatibility and radio-frequency engineering(2026); This thesis explores the use of machine learning (ML) in electromagnetic compatibility (EMC) engineering and related fields, focusing on common challenges such as model interpretability, high-dimensional design spaces, and data acquisition costs. It investigates ML methods that incorporate physical insights to improve modeling accuracy and reliability. Strategies to enhance data-efficiency and promote dataset reuse are proposed to support reproducibility and collaboration. Recommendations for future research and community efforts are provided to advance ML adoption in EMC and related fields. The results demonstrate the potential of ML to accelerate the design and modeling processes in EMC.Publicationtype: Doctoral Thesis31 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Planarer Dual-Polarisierter Gruppenstrahler für Duplexbetrieb im K-/Ka-Band(2025); In this work, a phased array for the K- and Ka-band is developed, manufactured and tested. A special feature of the phased array is the combination of the transmitting and receiving antennas in a single aperture, enabling full-duplex operation. Because the phased array is designed for mobile satellite communication, it employs a highly compact and planar design and two orthogonal polarizations.Publicationtype: Doctoral Thesis44 61 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Instrumentation, sequences and applications for magnetic particles in imaging and spectroscopy(2024); As an emerging medical imaging modality, magnetic particle imaging (MPI) has demonstrated considerable potential in imaging scenarios where established techniques are limited or have adverse effects. However, it still faces several challenges for future clinical integration and for achieving theoretical predictions of performance. MPI is a quantitative, tracer-based, and indirect imaging technique, that measures the non-linear response of magnetic nanoparticles (MNPs) at high temporal and spatial resolution with very high sensitivity. Major milestones such as the in vivo measurement of a beating mouse heart in 2009 or the first MPI-tailored MNPs in the same year, have been complemented by progress in various disciplines that constitute the research field of MPI. These include image reconstruction, signal encoding, MNP synthesis, applications and hardware instrumentation as main categories. Today, real-time reconstructions are feasible for perfusion imaging, as well as simultaneous measurement and signal separation of different MNP systems, and intentional interaction of MNPs with their immediate environment by mechanical activation, hyperthermia or targeted drug delivery. Initial progress toward the development of a full-scale, human-sized system by the Philips research division in Hamburg, Germany, in 2015 was accompanied by a number of challenges. The enormous engineering effort included the development of instrumentation needed to generate strong alternating and static magnetic fields in a cost-effective and maintainable manner, with a complexity similar to that of an Magnetic Resonance Imaging (MRI) system. Ultimately, the project struggled to maintain funding. At the Institute of Biomedical Imaging, Hamburg University of Technology, the challenge in instrumentation was addressed on a smaller scale, but still within the range of human proportions. A human-sized head scanner was introduced in 2019 that incorporated numerous straightforward solutions to previous difficulties, benefiting from smaller components and lower electrical specifications. A significant aspect of this thesis is the comprehensive redesign of this head-sized imaging system to align with clinical standards in terms of 3D acquisition speed, safety, and resolution. The design process incorporates both feasibility and clinical trial requirements, and achievable results are highlighted for an approved, but inferior, Ferucarbotran-based tracer. One part of this thesis is devoted to an in-depth examination of the transmit-receive signal chain of the device, accompanied by a comprehensive account of the development and design process of a high current linear toroidal transformer. The high-gain transformer can also be utilized in applications beyond medical imaging, operating in the kHz range, such as wireless power transmission. Another section in the present thesis investigates the suitability of a novel Ferucarbotran tracer, its MPI signal quality, composition, and performance in comparison to other MNPs. In the fields of neurology and interventional radiology, a head-sized imaging system can be employed for the prompt diagnosis of various types of stroke, including ischemic stroke, which represents a significant cause of mortality in the context of cardiovascular disease. Intracerebral hemorrhage represents the second most common type of stroke for which perfusion imaging serves as an invaluable diagnostic tool. Our head-sized imaging system may facilitate long-term monitoring of such patients. In this study, we propose a negative contrast perfusion imaging technique based on a long-circulating tracer and a saline bolus, which enables the repeated generation of trackable dynamic changes in MNP concentration without increasing the total administered iron dose. It leverages several significant advantages of MPI over other modalities, including its sensitivity, linearity, and high temporal resolution for 3D volume tracking, enabling not only concentration changes but also the rate of these processes to be monitored. Given the limited iron uptake by the liver and spleen, reducing the administered dose is a crucial aspect to consider for repeated monitoring of an individual patient. MNP spectrometry is a highly valuable tool during the preclinical stage of MPI, as it allows for the assessment and evaluation of the non-linear response and relaxation behavior with high signal quality and low noise in homogeneous fields. Concerning the instrumentation of MNP spectrometry, this work presents an arbitrary waveform magnetic particle spectrometer (MPS) for the purpose of measuring and emulating data, including the development and calibration of the device. This spectrometer is capable of measuring particles in a variety of excitation and offset fields. The data is then processed by a custom software framework, which assembles a realistic dataset that can be used for complex sequence emulation. In particular, the device can be utilized to assess different excitation types, MPI signal encoding, saturation behavior, and the magnetization behavior of nanoparticles on a small scale with short measuring times, typically below one minute.Publicationtype: Doctoral Thesis64 50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Hybrid-Integrierte Sendeempfangsmodule für Dual-Polarisierte Gruppenstrahler im K-/Ka-Band(2024); In this thesis, an active K-/Ka-band phased array for simultaneous transmit and receive operation with a shared antenna aperture is designed, manufactured and characterized. The modular system is polarization agile and intended for mobile satellite communications. It consists of a quasi-planar assembly of printed circuit boards and waveguide components. This hybrid integration approach helps to meet the space requirements resulting from phased array physics as well as electrical and thermal system requirements. The focus of the work is on the active and passive microwave circuits that are required to drive the antenna elements.Publicationtype: Doctoral Thesis80 145 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Manipulation of light transport in disordered media by reciprocal design(2023); In this work different aspects of the scattering of light in disordered optical structures are elucidated. The applicability of the Ewald sphere construction to non-iridescent structural colors is investigated by comparison of analytical to simulation results. Moreover, a mathematical derivation is presented and again tested against simulation, predicting the possibility of obtaining complete photonic bandgaps in structures with arbitrarily low refractive-index contrast.Publicationtype: Doctoral Thesis77 168 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A carrier-suppressing interferometer for ultra-low-noise amplitude- and phase-detection(2023); This thesis introduces the application of the Carrier-Suppression Interferometer (CSI) method for precision phase-noise measurements at attosecond resolution in the field of particle accelerator control systems. Starting from the thorough investigation of crucial system components and their phase noise contribution, the CSI setup reported here outperforms conventional noise detection methods for accelerator controls by more than two orders of magnitude. Furthermore, setup resolution limits and calibration methods are discussed.Publicationtype: Doctoral Thesis216 139 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Sende-Empfangsmodule für maritime Dualband-Radare mit aktiven GruppenstrahlernPublicationtype: Doctoral Thesis89 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Dual-polarisierte Gruppenstrahler für ein maritimes Zweifrequenz-RadaPublicationtype: Doctoral Thesis99 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Substrate integrated waveguide technology for Rx/Tx integrated array antennasThis work deals with an Rx/Tx integrated array antenna for mobile satellite communications at K/Ka-band. The realization is enabled by substrate integrated waveguide (SIW) technology, which is studied in-depth. A transmission line model for so-called multilayer substrate integrated waveguides is developed. It takes losses and conductors with rough surfaces into account. Based on the model, components are designed and, finally, assembled to realize a passive dual-polarized array antenna. This demonstrates that a significant size reduction is possible compared to separate antennas for Rx and Tx.Publicationtype: Doctoral Thesis262 2802