Open Source Reconfigurable Intelligent Surface for the Frequency Range of 5 GHz WiFi

Refonfigurable Intelligent Surfaces (RIS) have been idenitified as a potential ingredient to enhance the performance of contemporary wireless communication and sensing systems. Yet, most of the existing devices are either costly or not available for reproduction. To close this gap, a Reconfigurable Intelligent Surface for the frequency range of 5 GHz WiFi is presented in this work. We describe the designed unit cell, which is optimized for the full frequency range of 5.15 to 5.875 GHz. Standard FR4 substrate is used for cost optimization. The measured reflection coefficient of a rectangular RIS prototype with 256 elements is used for RF performance evaluation. Fabrication data and firmware source code are made open source, which makes RIS more available in real measurement setups

Characterization of Nematic Liquid Crystal at Microwave Frequencies Using Split-Cylinder Resonator Method

[EN] Liquid crystal (LC) is an anisotropic liquid material, which flows like a liquid, but at the same time, its molecules have an orientational order like in the solid state. Thus, LC is a promising dielectric material for designing reconfigurable devices at microwave frequencies. In order to optimize the design of reconfigurable microwave devices, accurate values of the dielectric permittivity and the loss tangent of LCs are needed. However, new LCs are not well characterized at these frequencies because of its recent use for microwave applications. Therefore, the characterization in this frequency range is required for its practical use within microwave components and devices. In this paper, a split-cylinder resonator method is used for the characterization of four different nematic LCs at two frequency points, i. e., 5 and 11 GHz. This characterization includes the extraction of their complex dielectric permittivity values at these frequencies. The employed method allows to obtain the two extreme permittivity values without applying any external electric or magnetic field to polarize the LC molecules. Two different approaches, a modal analysis method and a full-wave numerical technique, have been used for determining the LC parameters obtaining similar results in both cases.This work was supported in part by the Generalitat Valenciana Research under Project PROMETEOII/2015/005, in part by the Ministerio de Educacion, Cultura y Deporte, Spain, through the Fellowship Program for Training University Professors under Grant FPU14/00150, in part by the Ministerio de Economia y Competitividad, Spain through Research and Development Projects under Grant TEC2016-75934-C4-R-1, and in part by the Gobierno de Aragon-Fondo Europeo de Desarrollo Regional (FEDER)-Fondo Social Europeo 2017-2019 under Reference E14-7R.Sánchez-Marín, JR.; Nova-Giménez, V.; Bachiller Martin, MC.; Villacampa, B.; De La Rua, A.; Kronberger, R.; Penaranda-Foix, FL.... (2019). Characterization of Nematic Liquid Crystal at Microwave Frequencies Using Split-Cylinder Resonator Method. IEEE Transactions on Microwave Theory and Techniques. 67(7):2812-2820. https://doi.org/10.1109/TMTT.2019.2916790S2812282067

ERP hoch 3: Energieraumplanung entlang von ÖV-Achsen

Im Rahmen des national geförderten Forschungsprojekt „ERP_hoch3“ wird der Themenschwerpunkt Energieraumplanung in drei Fokusebenen betrachtet, untersucht und simuliert. Während „ERP“ für Energieraum-planung steht, steht die „3“ für drei verschiedene Raumbezüge – Stadtquartiere, öffentliche Verkehrsachsen und interkommunale Flächenpotenziale erneuerbarer Energien (Region). ERP_hoch3 ist ein zweijähriges Grundlagenforschungsprojekt, gefördert vom österreichischen Klimafonds. Das Forschungsteam besteht aus 14 Expertinnen und Experten der Fachbereiche für Regionalplanung und für örtliche Raumplanung (TU Wien, Department für Raumplanung) und der Institute für Städtebau und Prozess- und Partikeltechnik (TU Graz)

Measurement of the dielectric properties of liquid crystal material for microwave applications

[EN] Liquid Crystal (LC) is an anisotropic liquid material which flows like a liquid, but at the same time its molecules have an orientational order like in the solid state [1]. Thus, LC is a promising dielectric material for designing reconfigurable devices at microwave frequencies. In order to optimize the design of reconfigurable microwave devices, accurate values of the dielectric permittivity and the loss tangent of LCs are needed. However, new LCs are not well characterized at these frequencies because of its recent use for microwave applications. Therefore, the characterization in this frequency range is required for its practical use within microwave components and devices [2]. In this work, the split-cylinder resonator method has been used for the characterization of LCs at two frequency points, i.e. 5 and 11 GHz. The method is based on the measurement of the resonance frequency and quality factor of the two states of the LC molecules for extracting the complex dielectric permittivity [3]. For achieving these two states, no electric or magnetic fields are needed, just the cell must be turned 90º inside the cavity. The dielectric properties (permittivity and loss tangent) of four different LC samples, GT3-23002 from Merck and QYPD193, QYPD142, and QYPD036 from Qingdao QY Liquid Crystal Co, have been obtained. The highest values of the dielectric anisotropy are presented for the samples QYPD036 and QYPD193, together with the highest values of the corresponding loss tangent parameters. Furthermore, it is observed for all the LCs that the loss tangent decreases and the dielectric anisotropy increases at higher frequencies, which must be taken into account in the development of reconfigurable microwave devices.Sanchez, J.; Nova Giménez, V.; Bachiller Martin, MC.; Villacampa, B.; De La Rua, A.; Kronberger, R.; Peñaranda Foix, FL.... (2019). Measurement of the dielectric properties of liquid crystal material for microwave applications. En AMPERE 2019. 17th International Conference on Microwave and High Frequency Heating. Editorial Universitat Politècnica de València. 506-510. https://doi.org/10.4995/AMPERE2019.2019.998350651

4 Urschel, Nachtfräulein und andere Gespenster. Überlieferungen und Sagen in Reutlingen und Pfullingen

Beiträge zur Geschichte, Kunst- und Kulturgeschichte der Stadt und Region Reutlingen

A Printing Strategy for Embedding Conductor Paths into FFF Printed Parts

A novel approach to manufacture components with integrated conductor paths involves embedding and sintering an isotropic conductive adhesive (ICA) during fused filament fabrication (FFF). However, the molten plastic is deposited directly onto the adhesive path which causes an inhomogeneous displacement of the uncured ICA. This paper presents a 3D printing strategy to achieve a homogeneous cross-section of the conductor path. The approach involves embedding the ICA into a printed groove and sealing it with a wide extruded plastic strand. Three parameter studies are conducted to obtain a consistent cavity for uniform formation of the ICA path. Specimens made of polylactic acid (PLA) with embedded ICA paths are printed and evaluated. The optimal parameters include a groove printed with a layer height of 0.1 mm, depth of 0.4 mm, and sealed with a PLA strand of 700 µm diameter. This resulted in a conductor path with a homogeneous cross-section, measuring 660 µm ± 22 µm in width (relative standard deviation: 3.3%) and a cross-sectional area of 0.108 mm2 ± 0.008 mm2 (relative standard deviation 7.2%). This is the first study to demonstrate the successful implementation of a printing strategy for embedding conductive traces with a homogeneous cross-sectional area in FFF 3D printing

Winand Victor - Maler in Reutlingen

Band 46 von 2007 der Reutlinger Geschichtsblätter versammelt sechs Beiträge zur Geschichte Reutlingens und seiner Persönlichkeiten vom Mittelalter bis ins 20. Jahrhundert. Bauhistorische Untersuchungen zum Tübinger Tor, die private Chronik Johann Georg Launers sowie ein Porträt des Künstlers Winand Victor bilden die Schwerpunkte