المؤلفون: Manoliu, Laura, Hennenberger, Ralf, Tessmann, Axel, Seidel, Jochen, Eppard, Michael, Wrana, Dominik, Schoch, Benjamin, Kallfass, Ingmar

مصطلحات موضوعية: Atmospheric modeling, Millimeter wave propagation, Millimeter wave communication, E-band, Rain fading

الوصف: 208 ; 211 ; This paper is giving a summary about the atmospheric effects affecting millimeter wave communication systems for a point-to-point E-band link. The focus is on attenuation caused by water droplets. Experimental results obtained in Stuttgart, Germany, are presented to confirm the theoretical aspects discussed through this paper. Wideband complex modulated signals with up to 3.3 GBd symbol rate are used to model the atmospheric behavior of electromagnetic radio frequency signals on an E-band link (71-76 GHz), operated over 1.6 km distance. This paper reviews also the availability and fade margin targets of the new radio links by showing the correlation with the ITU models and recommendations.

العلاقة: German Microwave Conference 2022; #PLACEHOLDER_PARENT_METADATA_VALUE#; 14th German Microwave Conference, GeMiC 2022. Proceedings; https://publica.fraunhofer.de/handle/publica/418742Test

الإتاحة: https://publica.fraunhofer.de/handle/publica/418742Test

المؤلفون: Manoliu, Laura, Henneberger, Ralf, Tessmann, Axel, Seidel, Jochen, Eppard, Michael, Kallfass, Ingmar

مصطلحات موضوعية: Atmospheric modeling, Millimeter wave propagation, Millimeter wave communication, E-Band

الوصف: 990 ; 993 ; This paper analyses experimental data of the atmospheric propagation effects affecting millimeter wave communication links using wideband complex modulation formats with up to 3.3 GBd symbol rate. The main focus is on attenuation caused by atmospheric gases and water droplets and the influence of the air temperature and humidity on an E-band link (71–76 GHz), operated over 1.6 km distance for a period of more than 2 months. Statistics of the expected losses, according to the pertaining International Telecommunication Union models and some experimental results, as in the case of rain and snow attenuation, obtained in Stuttgart, Germany, are discussed and provide further insights in link stability and availability. 3.3 GBd are correctly transmitted regardless of the weather conditions. The presented link can also serve as calibration system for further atmospheric effects studies.

العلاقة: European Microwave Conference 2022; 51st European Microwave Conference, EuMC 2021; #PLACEHOLDER_PARENT_METADATA_VALUE#; EIVE-T; 50YB2101; https://publica.fraunhofer.de/handle/publica/425223Test

الإتاحة: https://doi.org/10.23919/EuMC50147.2022.9784215Test
https://publica.fraunhofer.de/handle/publica/425223Test

المؤلفون: Grunwald, Christoph, Durr, Nathanaël, Sauer, Martin, Riedel, Werner, Hiermaier, Stefan

مصطلحات موضوعية: hydrocode, mesoscale, microscale, multiscale, staggered coupling, wave propagation

الوقت: 620

الوصف: S.6361-6383 ; This article proposes an efficient concurrent coupling of two different material scales-a macroscale and a microscale-in a direct solution scheme based on explicit time integration. Both scales may be discretized with different element sizes and the microdomain may exhibit a heterogeneous structure. A surface coupling is described, which imposes the macrovelocities at the interfaces on the microscale. Using an averaged stress state of several elements on the microscale within a bounded volume, forces are derived which transfer the micromaterial response back to the macroscale. Whereas established surface couplings based on Lagrange multipliers achieve an exact solution of the interface problem, the proposed coupling is based on a weak staggered scheme. The advantage is that no common global system of equations has to be solved and the approach preserves the efficiency of direct solution schemes almost completely. It is therefore well applicable to the simulation of wave propagation phenomena in heterogeneous materials with complex constitutive models and suitable for massive parallelization. Example simulations demonstrate the capabilities and current limitations. ; 122 ; Nr.21

العلاقة: International journal for numerical methods in engineering; https://publica.fraunhofer.de/handle/publica/269320Test

الإتاحة: https://doi.org/10.1002/nme.6795Test
https://publica.fraunhofer.de/handle/publica/269320Test

المؤلفون: Breunig, Ingo, Buse, Karsten

مصطلحات موضوعية: optical parametric oscillator, light wave propagation, lithium niobate, phase matching, refractive index, wavelength tuning, spectroscopy, whispering Gallery Resonator

الوقت: 621

الوصف: Paper 109020T, 7 S. ; Optical parametric oscillators (OPOs) convert the frequency of laser light to almost arbitrary values. Nowadays, they serve as wavelength-agile light sources for spectroscopic applications as well as photon generators for quantum-optical experiments. Conventional OPOs are based on a nonlinear-optical crystal surrounded by a mirror cavity. Regarding the cavity, one often finds the following rule of thumb: the more waves are resonant, the lower is the oscillation threshold and the more difficult is the wavelength tuning. In whispering-gallery-resonator-based OPOs (WGR OPOs), light is guided by total internal reflection in a millimeter-sized spheroidally-shaped nonlinear-optical crystal. Thus, these devices are intrinsically triply resonant. Indeed, they provide microwatt-level oscillation thresholds, i.e., the lowest values of all OPO configurations. However, following the abovementioned rule, their applicability in fields beyond fundamental science might be questionable, because the most striking feature of an OPO, i.e., the wavelength tunability, is hampered. Nevertheless, several experimental studies revealed that the output wavelengths of WGR OPOs could be tuned in well-defined steps over hundreds of nanometers by temperature variation. Combined with strategies for mode-hop free tuning, it is possible, e.g., to tune the output wavelength in a controlled way until it meets MHz-wide resonances. This is sufficient for high-resolution spectroscopy. WGR OPOs are nowadays operated around various center frequencies, covering the visible-to-mid-infrared spectral range. These light sources - despite of their intrinsic triple resonance - might serve as compact and wavelength-agile devices for various applications.

العلاقة: Conference "Nonlinear Frequency Generation and Conversion - Materials and Devices" 2019; Nonlinear Frequency Generation and Conversion: Materials and Devices XVIII; https://publica.fraunhofer.de/handle/publica/404051Test

الإتاحة: https://doi.org/10.1117/12.2509240Test
https://publica.fraunhofer.de/handle/publica/404051Test

المؤلفون: Mueller, Inka, Moll, Jochen, Tschöke, Kilian, Prager, Jens, Kexel, Christian, Schubert, Lars, Lugovtsova, Yevgeniya, Bach, Martin, Vogt, Thomas

مصطلحات موضوعية: guided electromagnetic wave propagation, Life Cycle, monitoring, nondestructive examination, reliability, signal processing, survey, efficient simulation, engineering structures, environmental influence, non-destructive testing, probability of detection, scientific community, simulation algorithm, structural health monitoring (SHM)

الوقت: 620, 666

الوصف: S.787-794 ; Not all issues that prevent Structural Health Monitoring (SHM) based on Guided Waves (GW) from being a part of today's monitoring solutions in industry are obvious to the scientific community. To uncover and overcome these issues, scientists working on SHM and GW problems joined in an expert committee under the patronage of the German Society for Non-Destructive Testing. An online survey among more than 700 experts and users reveals the hurdles hindering the practical application of GW-based SHM. Firstly, methods for proof of reliability of SHM " approaches are missing. Secondly, detailed understanding of phenomenological described wave-damage interactions is needed. Additionally, there are significant unsolved implementation issues and un-solved problems of signal processing including handling of environmental influences. To enable substantial proof of reliability without unaffordable experimental effort also efficient simulation tools including realistic damage interaction are needed, enabling the joint use of experimental and simulated data to predict the capabilities of the monitoring system. Considering these issues, the committee focusses on simulation, signal processing, as well as probability of detection and standardization. In the presented work, recent activities of the expert committee starting with survey results are summarized. An open access data basis of life-like measurements is presented to allow testing and comparison of signal processing and simulation algorithms. Finally, a strategy for efficient proof of reliability increasing the acceptance of SHM in industry and for successful integration of SHM into real-world engineering structures is proposed.

العلاقة: International Workshop on Structural Health Monitoring (IWSHM) 2019; Structural Health Monitoring 2019. Vol.1; https://publica.fraunhofer.de/handle/publica/405646Test

الإتاحة: https://publica.fraunhofer.de/handle/publica/405646Test

المؤلفون: Neubauer, Philipp, Bös, Joachim, Melz, Tobias

مصطلحات موضوعية: dynamics of nano-systems, numerical modelling or physical experiments, structural vibration/elastic wave propagation (including fluid-loaded structures, piezoelectric materials, and granular media), gear noise, Gear Whine, Uneven Excitation, tonality

الوقت: 620, 621, 534, 006

الوصف: Art. 115234 ; Randomizing the periodic excitation is a well-known noise reduction measure, for example in fans and tire patterns. Due to a randomized excitation the tonal components of the generated noise are reduced while broadband noise is increased in amplitude. This less tonal noise with a more broadband character is perceived less annoying. In the presented research this approach is applied to gears - called inequidistant gears. They are characterized by uneven tooth positions and uneven tooth thicknesses. The deviations from regular, perfectly even gears may be up to several millimeters in both position and thickness. In the same way as in fans and tire patterns, the uneven design of inequidistant gears leads to a less tonal and less annoying noise. In this paper the design of inequidistant gears is introduced. Equations are derived to define the uneven geometry of an inequidistant gear wheel and to exactly match a pair of meshing inequidistant gears. The presented approach is valid for spur gears, helical gears, and double helical gears, but only spur gears are considered in this paper. Furthermore, a method to calculate the gear mesh stiffness, which is the main excitation mechanism in gear noise, and a method to calculate the gear mesh forces are presented. Experimental investigations are carried out on a back-to-back gear test bench. The calculated gear mesh force and the experimentally determined sound pressure of a regular, perfectly even spur gear set are compared to those of an equivalent inequidistant spur gear set. The results reveal that inequidistant gears not only reduce the tonality but are - in contrast to uneven designs of fans and tire patterns - capable of reducing the total sound pressure level. ; 473

العلاقة: Journal of Sound and Vibration; https://publica.fraunhofer.de/handle/publica/261992Test

الإتاحة: https://doi.org/10.1016/j.jsv.2020.115234Test
https://publica.fraunhofer.de/handle/publica/261992Test

المؤلفون: Meier, Dominik, Zech, Christian, Baumann, Benjamin, Gashi, Bersant, Schlechtweg, Michael, Kühn, Jutta, Rösch, M., Reindl, Leonard M.

مصطلحات موضوعية: composite materials, coupled mode analysis, electromagnetic modeling, millimeter wave propagation, millimeter wave radar

الوقت: 667, 621

الوصف: S.3080-3093 ; Composite materials have become indispensable in a wide variety of technical fields, where they are viewed as the key technological component. Due to their structural complexity, these materials are prone to errors while in the manufacturing process, thus non-destructive inspecting becomes a crucial step in the processing chain and further maintenance of said material. However, a tomographic characterization of these components is often only possible to a limited extent-a capability which is essential to exploit the full potential of this technology. Measurement systems based on millimeter waves (mmWs) have the potential to achieve exactly that, by providing valuable information on the internal structure of such components. Yet, these non-destructive and non-contact methods have not found wide usage in practical applications. One reason for this is that the effects composite materials have on the propagation behavior of mmW signals have not been a major subject of study in the past. Therefore, a model for predicting the propagation properties of mmW signals in composite materials is presented here. Based on coupled wave analysis, the propagation of arbitrary electromagnetic signals in composite materials can be simulated. These results can be directly incorporated into the design of respective measurement systems. The introduced model is verified through a comparison of simulation and measurement results, obtained via a focused frequency modulated continuous wave (FMCW) radar, operating in the H-band (220-325 GHz), directed at glass fiber reinforced plastic samples. ; 68 ; Nr.4

العلاقة: IEEE Transactions on Antennas and Propagation; https://publica.fraunhofer.de/handle/publica/263495Test

الإتاحة: https://doi.org/10.1109/TAP.2019.2955213Test
https://publica.fraunhofer.de/handle/publica/263495Test

المؤلفون: Worku, N.G., Gross, H.

مصطلحات موضوعية: electric field, electromagnetic wave propagation, Gaussian beam, Gaussian distribution, optical system

الوقت: 620, 535

الوصف: S.98-107 ; Many applications of ultrashort laser pulses require manipulation and control of the pulse parameters by propagating them through different optical components before the target. This requires methods of simulating the pulse propagation taking into account all effects of dispersion, diffraction, and system aberrations. In this paper, we propose a method of propagating ultrashort pulses through a real optical system by using the Gaussian pulsed beam decomposition. An input pulse with arbitrary spatial and temporal (spectral) profiles is decomposed into a set of elementary Gaussian pulsed beams in the spatiospectral domain. The final scalar electric field of the ultrashort pulse after propagation is then obtained by performing the phase correct superposition of the electric fields all-Gaussian pulsed beams, which are propagated independently through the optical system. We demonstrate the application of the method by propagating an ultrashort pulse through a focusing aspherical lens with large chromatic aberration and a Bessel-X pulse generating axicon lens. ; 37 ; Nr.1

العلاقة: Journal of the Optical Society of America. A, Optics, image science, and vision; https://publica.fraunhofer.de/handle/publica/261028Test

الإتاحة: https://doi.org/10.1364/JOSAA.37.000098Test
https://publica.fraunhofer.de/handle/publica/261028Test

المؤلفون: Wang, Yongheng, Gao, Xiaorong, Netzelmann, Udo

مصطلحات موضوعية: backward thermal wave propagation, coating, crack, induction thermography

الوقت: 620, 658, 670

الوصف: Paper Th.4.B.3 ; The effect of non-metallic polymer coatings on the induction thermographic signal from metal surfaces with cracks was studied. Analytical calculations for the backward thermal wave propagation were performed both in the frequency and in the time domain. Numerical simulations were used to show the thermal patterns of cracks under coatings. Experiments were performed on coated samples with artificial cracks. The crack contrast was analysed under coatings of various thickness. The contrast in amplitude and phase is decreasing with coating thickness. The effect of infrared transparency of a model coating was shown in experiment.

العلاقة: Quantitative InfraRed Thermography Conference (QIRT) 2018; 14th Quantitative InfraRed Thermography Conference, QIRT 2018; https://publica.fraunhofer.de/handle/publica/401304Test

الإتاحة: https://publica.fraunhofer.de/handle/publica/401304Test

المؤلفون: Peter, Michael, Weiler, Richard J., Undi, Fabian, El-Kanawati, Farouk, Jaeckel, Stephan, Raschkowski, Leszek, Thiele, Lars, Sakaguchi, Kei, Keusgen, Wilhelm

مصطلحات موضوعية: channel measurement, mm-wave propagation, delay spread, frequency dependence

الوقت: 621

الوصف: S.616-617 ; A channel measurement campaign was carried out in Berlin, Germany, aiming to provide multi-frequency data for the urban microcellular (UMi) access channel in the street canyon. Four bands (10.25, 28.5, 41.5 and 82.5 GHz) were measured simultaneously. In this paper, statistical evaluations on the frequency dependence of the root-mean-square delay spread (DS) under line of sight (LOS) conditions are presented. The largest values occur for 10.25 GHz when a high relative evaluation threshold is used, and the values are smallest for 82.5 GHz. However, a distinct and clear frequency dependence cannot be observed for the measured scenario. The estimated DS is very sensitive to data selection and processing.

وصف الملف: application/pdf

العلاقة: International Symposium on Antennas and Propagation (ISAP) 2016; International Symposium on Antennas and Propagation, ISAP 2016; mmMAGIC; 671650; https://publica.fraunhofer.de/handle/publica/397249Test

الإتاحة: https://doi.org/10.24406/publica-fhg-397249Test
https://publica.fraunhofer.de/handle/publica/397249Test