Measurement testbed for radar and emitter localization of UAV at 3.75 GHz. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 5 S.
This paper presents an experimental measurement platform for the research and development of unmanned aerial vehicles (UAVs) localization algorithms using radio emission and reflectivity. We propose a cost-effective, flexible testbed made from commercial off-the-shelf (COTS) devices to allow academic research regarding the upcoming integration of UAV surveillance in existing mobile radio networks in terms of integrated sensing and communication (ISAC). The system enables nanosecond-level synchronization accuracy and centimeter-level positioning accuracy for multiple distributed sensor nodes and a mobile UAV-mounted node. Results from a real-world measurement in a 16 km^2 urban area demonstrate the system’s performance with both emitter localization as well as with the radar setup.
Spatial/temporal characterization of propagation and blockage from measurements at sub-THz in industrial machines. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 5 S.
In the present paper we introduce novel ultra-wideband (UWB) dual-polarized double-directional measurements at sub-THz (300 GHz) in an access point to inside of machine application in an industrial scenario. The results show a sparse spatial/temporal channel with multiple paths from the different metallic objects and their influence on polarization. In addition, different LOS blockage situations were investigated, showing the presence of alternative paths for communications.
Measurement-based analysis of multi-band assisted beam-forming at mmWave in industrial scenarios. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 5 S.
The mmWave and sub-THz bands are foreseen as candidates to achieve the data-rate demands in the beyond 5G and 6G wireless communication networks. The co-existence of multiple radio interfaces at several bands enables data fusion and the utilization of the similarities and differences on propagation and system properties for communication and sensing applications. MmWave radio interfaces rely on directive beams that require high training overhead for beam steering. Sensors in the network infrastructure and co-located radio interfaces at sub-6 GHz and mmWave can be used to assist the beam-forming process at mmWave. In the present paper we investigate the performance of multi-band assisted beam-forming in an industrial environment. We empirically demonstrate from real-world measurements that even in NLOS, the direction of the beams estimated at sub-6 GHz can be used to established a link at mmWave.
Reduction of mutual coupling between dual-polarized antenna elements using defected ground structures. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 5 S.
To accurately model a communication channel using channel sounding technique, having dual-polarized antenna elements and low mutual coupling between them is required. In this work a Defected Ground Structure (DGS) is proposed to reduce the mutual coupling between two dual polarized mmWave antenna elements in an array structure. The defected ground is made of etched C-shape slots. The presence of the DGS has a strong impact on H-plane coupling where a suppression of 35 dB is achieved, while the reduction of E-plane coupling is about 4 dB. The unwanted effect on the radiation patterns is negligible and the back radiation is not increased.
N˚69 - N-Interval fourier transform analysis of cortical evoked responses - Median and tibial SEPs. - In: Clinical neurophysiology, ISSN 1872-8952, Bd. 150 (2023), S. e93-e94
Multi-environment based meta-learning with CSI fingerprints for radio based positioning. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 6 S.
Radio based positioning of a user equipment (UE) based on deep learning (DL) methods using channel state information (CSI) fingerprints have shown promising results. DL models are able to capture complex properties embedded in the CSI about a particular environment and map UE’s CSI to the UE’s position. However, the CSI fingerprints and the DL models trained on such fingerprints are highly dependent on a particular propagation environment, which generally limits the transfer of knowledge of the DL models from one environment to another. In this paper, we propose a DL model consisting of two parts: the first part aims to learn environment independent features while the second part combines those features depending on the particular environment. To improve transfer learning, we propose a meta learning scheme for training the first part over multiple environments. We show that for positioning in a new environment, initializing a DL model with the meta learned environment independent function achieves higher UE positioning accuracy compared to regular transfer learning from one environment to the new environment, or compared to training the DL model from scratch with only fingerprints from the new environment. Our proposed scheme is able to create an environment independent function which can embed knowledge from multiple environments and more effectively learn from a new environment.
Framework for simulation models and algorithms in ISAC networks. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 6 S.
In Integrated Sensing and Communications (ISAC), radar and communications functionalities share the same radio channel and radio resources. This sharing allows the deployment of both functionalities at a low cost without additional frequency bands and infrastructure. Because radar and communications have different radio resource requirements, new radio access and radio resource management (RRM) methods are required in a shared system. To develop and evaluate new ISAC methods, this paper presents a modular simulation framework for the system level and link level of ISAC networks. The main components of the framework are the data storage, the simulators, and the algorithms. This paper presents the framework's architecture, the integrated simulation models for channel and signal simulation, and the integrated algorithms for multiple radar target localization and data transmission.
Reactive die bonding on LTCC substrates - analysis by CFD simulation. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 5 S.
To improve the understanding of reactive multilayer systems as a joining process computational fluid dynamics (CFD) simulations have been performed and compared with experimental measurements made using a pyrometer. These CFD simulations consist of a shoebox model which contains different layers. The layers in the model are an Ni/Al reactive multilayer, low temperature co-fired ceramic (LTCC) substrate and the surrounding air environment. To simulate the heat released by the multilayer system, a user defined function of probability density function (PDF) form was written for the heat source. The peak energy intensity, reaction width and reaction speed can be controlled via the PDF to adapt the simulation to the real model.
Vascular MPI: visualization and tracking of rapidly moving samples. - In: International journal on magnetic particle imaging, ISSN 2365-9033, Bd. 9 (2023), 1, 2303044, S. 1-3
Magnetic Particle Imaging (MPI) is a fast imaging technique for the visualization of the distribution of superparamagnetic iron-oxide nanoparticles (SPIONs) in 3D. For spatial encoding, a field free area is moved rapidly through the field of view (FOV) generating a localized signal. Fast moving samples, e.g., a bolus of SPIONs traveling through the large veins in the human body carried by blood flow with velocities in the order of ˜45 cm/s and higher, cause temporal blurring in MPI measurements using common sequences and reconstruction techniques. This hampers the evaluation of dynamics of rapidly moving samples. In this abstract, initial results of rapidly moving samples in form of SPION boluses visualized within an MPI scanner are shown.
MHD flow of submerged jets behind the inlet disturbance. - In: Proceedings in applied mathematics and mechanics, ISSN 1617-7061, Bd. 22 (2023), 1, e202200200, S. 1-6
In a broad variety of configurations in technology and industrial applications, the properties of liquid metal flows subjected to strong magnetic fields, are largely governed by the dynamics of coherent structures, known to settle several basic types, such as thin shear layers, forming near the walls or within the fluid domain, vortices extended along the field, or planar and round jets. In some cases, these structures are created by the design, like a submerged jet formed by a sudden expansion from the nozzle into a blanket channel, or jets formed behind some flow obstruction. In the other cases this may be due to instability and evolution of secondary structures, for example, descending and ascending jets appearing as a result of convective instability in blanket channels. In this study, we undertake an attempt to affect liquid metal flow via inlet disturbance formed by a simple rod placed along the magnetic induction lines. The disturbance can generate flat jets behind the rod and, furthermore, a sustainable flow of anisotropic vortical perturbations further downstream the flow. We seek to analyze the most important mechanisms of the flow dynamics and effects of magnetic field on the integral system properties of enhancing mixing, mass and heat transport for such flow. The most optimal regimes of vortex generation are found to be governed by the magnetic interaction parameter (Stuart number). The exact ratio of the optimal Stuart number is found to be in a range between 20 and 40, based on the channel double width as a characteristic size. The observed vortices attain quasi-2D shape and exist at a length of dozens of duct calibers, being the strongest at higher flow rates. The obtained flow regimes and their turbulent properties are also found to resemble significant similarity to the results on quasi-2D turbulence found in prior studies of channel and duct flows under spanwise magnetic field.