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  • 1
    Online Resource
    Online Resource
    Berlin :Humboldt-Universität zu Berlin,
    UID:
    almahu_BV049644424
    Format: 1 Online-Ressource.
    Edition: [Zweitveröffentlichung]
    Language: English
    URL: Volltext  (kostenfrei)
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  • 2
    UID:
    edochu_18452_28494
    Format: 1 Online-Ressource (9 Seiten)
    Content: This paper gives an overview of frequency regulation, standardization, and applications of 60 GHz communication systems. Based on forecasted developments of mobile IP traffic, the motivation for investigating circuits, and systems for the 60 GHz band is underlined. Some physical properties of 60 GHz radio waves are outlined and implications on potential applications are sketched. The current international and European frequency regulation aspects are presented. The main parameters of three different international standards are summarized and compared with each other. Details of channel spacing and channel bonding are given. Based on the investigation of different applications, the main system requirements are derived. Finally, some information on protocol issues and system integration aspects are given.
    Content: Peer Reviewed
    Note: This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.
    In: Cambridge : Cambridge Univ. Press, 3,2, Seiten 89-97
    Language: English
    URL: Volltext  (kostenfrei)
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  • 3
    UID:
    edochu_18452_25350
    Format: 1 Online-Ressource (23 Seiten)
    Content: Thermal Magnetic Resonance (ThermalMR) leverages radio frequency (RF)-induced heating to examine the role of temperature in biological systems and disease. To advance RF heating with multi-channel RF antenna arrays and overcome the shortcomings of current RF signal sources, this work reports on a 32-channel modular signal generator (SGPLL). The SGPLL was designed around phase-locked loop (PLL) chips and a field-programmable gate array chip. To examine the system properties, switching/settling times, accuracy of RF power level and phase shifting were characterized. Electric field manipulation was successfully demonstrated in deionized water. RF heating was conducted in a phantom setup using self-grounded bow-tie RF antennae driven by the SGPLL. Commercial signal generators limited to a lower number of RF channels were used for comparison. RF heating was evaluated with numerical temperature simulations and experimentally validated with MR thermometry. Numerical temperature simulations and heating experiments controlled by the SGPLL revealed the same RF interference patterns. Upon RF heating similar temperature changes across the phantom were observed for the SGPLL and for the commercial devices. To conclude, this work presents the first 32-channel modular signal source for RF heating. The large number of coherent RF channels, wide frequency range and accurate phase shift provided by the SGPLL form a technological basis for ThermalMR controlled hyperthermia anti-cancer treatment.
    Content: Peer Reviewed
    In: Basel : MDPI, 12,7
    Language: English
    URL: Volltext  (kostenfrei)
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  • 4
    UID:
    edochu_18452_27690
    Format: 1 Online-Ressource (22 Seiten)
    Content: Clock synchronization has always been a major challenge when designing wireless networks. This work focuses on tackling the time synchronization problem in 5G networks by adopting a hybrid Bayesian approach for clock offset and skew estimation. Furthermore, we provide an in-depth analysis of the impact of the proposed approach on a synchronization-sensitive service, i.e., localization. Specifically, we expose the substantial benefit of belief propagation (BP) running on factor graphs (FGs) in achieving precise network-wide synchronization. Moreover, we take advantage of Bayesian recursive filtering (BRF) to mitigate the time-stamping error in pairwise synchronization. Finally, we reveal the merit of hybrid synchronization by dividing a large-scale network into local synchronization domains and applying the most suitable synchronization algorithm (BP- or BRF-based) on each domain. The performance of the hybrid approach is then evaluated in terms of the root mean square errors (RMSEs) of the clock offset, clock skew, and the position estimation. According to the simulations, in spite of the simplifications in the hybrid approach, RMSEs of clock offset, clock skew, and position estimation remain below 10 ns, 1 ppm, and 1.5 m, respectively.
    Content: Peer Reviewed
    In: Heidelberg : Springer, 2021,1
    Language: English
    URL: Volltext  (kostenfrei)
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  • 5
    UID:
    almahu_BV024777439
    Format: 146 S., Anh. : , Ill.
    Note: Berlin, Humboldt-Univ., Math.-Naturwiss. Fak., Diss., 1992
    Language: German
    Keywords: Hochschulschrift
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  • 6
    UID:
    edochu_18452_29933
    Format: 1 Online-Ressource (22 Seiten)
    Content: Glioblastoma multiforme (GBM) is the most lethal and common brain tumor. Combining hyperthermia with chemotherapy and/or radiotherapy improves the survival of GBM patients. Thermal magnetic resonance (ThermalMR) is a hyperthermia variant that exploits radio frequency (RF)-induced heating to examine the role of temperature in biological systems and disease. The RF signals’ power and phase need to be supervised to manage the formation of the energy focal point, accurate thermal dose control, and safety. Patient position during treatment also needs to be monitored to ensure the efficacy of the treatment and avoid damages to healthy tissue. This work reports on a multi-channel RF signal supervision module that is capable of monitoring and regulating RF signals and detecting patient motion. System characterization was performed for a broad range of frequencies. Monte-Carlo simulations were performed to examine the impact of power and phase errors on hyperthermia performance. The supervision module’s utility was demonstrated in characterizing RF power amplifiers and being a key part of a feedback control loop regulating RF signals in heating experiments. Electromagnetic field simulations were conducted to calculate the impact of patient displacement during treatment. The supervision module was experimentally tested for detecting patient motion to a submillimeter level. To conclude, this work presents a cost-effective RF supervision module that is a key component for a hyperthermia hardware system and forms a technological basis for future ThermalMR applications.
    Content: Peer Reviewed
    In: Basel : MDPI, 13,5
    Language: English
    URL: Volltext  (kostenfrei)
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