ALBERT

Description: State determination of catalytic converters based on an ultra-wideband communication system Journal of Sensors and Sensor Systems, 4, 255-262, 2015 Author(s): I. Motroniuk, R. Stöber, and G. Fischerauer A novel microwave-based approach for monitoring the state of aftertreatment systems such as diesel particulate filters (DPFs), three-way catalytic converters (TWCs), and selective catalytic reduction (SCR) catalysts is proposed. The volume inside the metallic housing of the DPF, TWC, or SCR is considered as a wireless communication channel between two terminals of a communication system. It is shown that, depending on the transmission channel characteristics, the properties of the catalyst, such as the catalyst state, can be inferred. This is done by means of an ultra-wideband (UWB) measurement and the subsequent evaluation and processing of the waveform in the time and frequency domains.

Description: On the use of electrochemical multi-sensors in biologically charged media Journal of Sensors and Sensor Systems, 4, 295-303, 2015 Author(s): S. Sachse, A. Bockisch, U. Enseleit, F. Gerlach, K. Ahlborn, T. Kuhnke, U. Rother, E. Kielhorn, P. Neubauer, S. Junne, and W. Vonau For the investigation and characterisation of liquid media with microorganisms, electrochemical sensors are typically used. Usually the microorganisms are part of the process or cannot be excluded for different reasons. This paper describes the application of various electrodes, which are partly miniaturised and combined with multi-sensor systems for several applications in processes containing microorganisms. The application in industrial bioprocesses like beer brewing and biogas production, and in paper manufacturing, is described. The performance of the multi-sensor systems, and thus their suitability for a contribution to improved process monitoring, is evaluated. The multi-sensor systems represent an interesting tool to enhance monitoring capacities at installed systems without the necessity for huge port installations and offer the possibility to monitor the spatial distribution of gradients. The developed systems presented here allow location-independent measurements in process plants with a variable positioning of the sensors in the industrial reactors.

Description: Self-sufficient sensor for oxygen detection in packaging via radio-frequency identification Journal of Sensors and Sensor Systems, 4, 179-186, 2015 Author(s): C. Weigel, M. Schneider, J. Schmitt, M. Hoffmann, S. Kahl, and R. Jurisch A new disposable radio-frequency identification (RFID) sensor for detecting oxygen in packages with a protective atmosphere is presented. For safety reasons and system costs in consumer packages, no battery or energy harvesting devices can be used. Each part of a package, especially in food packaging, must be completely safe even if it is swallowed. Several materials have been investigated that safely react with oxygen and thus change electrical parameters without the need of an additional energy supply. In particular linseed oil was tested, because it is known to react in oxygen-containing atmosphere from liquid to solid. Linseed oil is used not only as food but also as a key part in ecological paint coatings. A significant relative change of capacity was observed during linseed oil drying, which results in −20% after 5 h and −38% after 30 h at an oxygen concentration of 20.5 and 50% relative humidity, respectively. Pure unsaturated fatty acids were also tested in an oxygen-containing atmosphere and showed similar behaviour. The reaction speed is partially dependent on the level of unsaturation of fatty acids. The oxygen sensor is coupled with an RFID front end with an internal charge time measurement unit for capacity determination. The combination of sensor element, sensitive material and RFID allows for biocompatible and save systems that indicate the presence of oxygen within a package.

Description: Increasing the sensitivity of electrical impedance to piezoelectric material parameters with non-uniform electrical excitation Journal of Sensors and Sensor Systems, 4, 217-227, 2015 Author(s): K. Kulshreshtha, B. Jurgelucks, F. Bause, J. Rautenberg, and C. Unverzagt To increase the robustness and functionality of piezoceramic ultrasonic sensors, e.g. for flow, material concentration or non-destructive testing, their development is often supported by computer simulations. The results of such finite-element-based simulations are dependent on correct simulation parameters, especially the material data set of the modelled piezoceramic. In recent years several well-known methods for estimation of such parameters have been developed that require knowledge of the sensitivity of a measured behaviour of the material with respect to the parameter set. One such measurable quantity is the electrical impedance of the ceramic. Previous studies for radially symmetric sensors with holohedral electrode setups have shown that the impedance shows little or no sensitivity to certain parameters and simulations reflect this behaviour making parameter estimation difficult. In this paper we have used simulations with special ring-shaped electrode geometry and non-uniform electrical excitation in order to find electrode geometries, with which the computed impedance displays a higher sensitivity to the changes in the parameter set. We find that many such electrode geometries exist in simulations and formulate an optimisation problem to find the local maxima of the sensitivities. Such configurations can be used to conduct experiments and solve the parameter estimation problem more efficiently.

Description: Simulation model for the evaluation and design of miniaturized non-resonant photoacoustic gas sensors Jochen Huber, Katrin Schmitt, and Jürgen Wöllenstein J. Sens. Sens. Syst., 5, 293-299, doi:10.5194/jsss-5-293-2016, 2016 A simulation model to predict system behaviour of photoacoustic CO 2 sensors is presented. The sensor output signal that depends on the CO 2 concentration can be simulated if the boundary conditions of the system are known. A comparison of simulated values with experimental results is made. There is good accordance between simulation and experiments. Photoacoustic gas sensors offer great potential for miniaturized gas sensors. The simulation model is an effective tool for further developments.

Description: Microfluidic measurement of cell motility in response to applied non-homogeneous DC electric fields Marisa Rio, Sharanya Bola, Richard H. W. Funk, and Gerald Gerlach J. Sens. Sens. Syst., 5, 237-243, doi:10.5194/jsss-5-237-2016, 2016 Endogeneous electric fields (EFs) affect a wide range of cellular functions such as migration, wound healing and regeneration. Similar results were observed when external EFs are applied. To date, the phenomenon of electrotaxis has been studied only in homogeneous EF environments. Here, we report on the construction and fabrication of a microfluidic biochip as well as first results for stimulation of cells with stationary, non-homogeneous EFs.

Description: Gas sensors based on plasma-electrochemically oxidized titanium foils Mhamed El Achhab and Klaus Schierbaum J. Sens. Sens. Syst., 5, 273-281, doi:10.5194/jsss-5-273-2016, 2016 We have developed a preparation technique to form graphite/TiO 2 /Ti and platinum-graphite/TiO 2 /Ti solid-state sensors based on plasma electrolytic oxidation (PEO) of titanium foils, whereby a porous titanium oxide layer is formed with well-defined phase composition and a reproducible microstructure. A printing method is used to deposit graphite or catalytically active graphite-platinum electrodes. Our design enables the application of many different detection principles such as calorimetry.

Description: Ultrafast imaging Raman spectroscopy of large-area samples without stepwise scanning Elmar Schmälzlin, Benito Moralejo, Daniel Bodenmüller, Maxim E. Darvin, Gisela Thiede, and Martin M. Roth J. Sens. Sens. Syst., 5, 261-271, doi:10.5194/jsss-5-261-2016, 2016 Imaging astronomy spectrographs are designed for recording thousands of spatially resolved spectra of a two-dimensional image field within one single exposure. Transferring this technology to imaging Raman spectroscopy allows a considerably faster acquisition of chemical maps. Within the scope of a research project, this method is refined for medical diagnostics, e.g., the identification of potentially cancerous abnormalities of skin tissue.

Description: Comparing mobile and static assessment of biomass in heterogeneous grassland with a multi-sensor system Hanieh Safari, Thomas Fricke, Björn Reddersen, Thomas Möckel, and Michael Wachendorf J. Sens. Sens. Syst., 5, 301-312, doi:10.5194/jsss-5-301-2016, 2016 This study aimed to explore the potential of a multi-sensor system for assessment of biomass in pastures under different grazing intensities. Prediction accuracy with a mobile application of sensors was always lower than when sensors were applied statically. However accuracy of biomass prediction improved with increasing grazing intensity. Although the limitations associated with the system especially in very lenient pastures, the finding opens up a perspective for future grazing management.

Description: Implantable biomedical sensor array with biocompatible hermetic encapsulation Carola Jorsch, Ulrike Schmidt, David Ulkoski, Carmen Scholz, Margarita Guenther, and Gerald Gerlach J. Sens. Sens. Syst., 5, 229-235, doi:10.5194/jsss-5-229-2016, 2016 The treatment of metabolic diseases, such as diabetes mellitus, requires sensitive measuring systems. These should be able to detect the different metabolism-related parameters (blood glucose level, pH, p CO 2 ) simultaneously and continuously. A new approach is an implantable wireless sensor microarray consisting of several hydrogel-based piezoresistive sensors that can provide an on-line monitoring of physiological parameters in the human body fluid. The specifically customized stimuli-responsive hydrogels enable the development of reliable biosensors for different analytes. In this regard, the on-line medical diagnostics attracts the main interest. The developed sensor system and its encapsulation should correspond to high requirements on the biocompatibility of implants according to the medical standard DIN EN ISO 10993-5. A multi-layer sensor encapsulation consisting of parylene C and amphiphilic block copolymers was proposed for subcutaneous implants and characterized using contact angle measurements and X-ray photoelectron spectroscopy. In vitro studies with model cells showed no cytotoxicity of the polyethylene glycol-based block copolymers. In order to understand the behavior of implants under physiological conditions, the interaction of the implant surface with biological specimen like proteins is discussed, taking into account the possible protein adsorption on the implant surface due to tissue inflammation around the implant, which should be minimized. Finally, the biocompatibility of the developed sensor system was studied to prove the suitability of the approach.

Description: Employing electro-mechanical analogies for co-resonantly coupled cantilever sensors Julia Körner, Christopher F. Reiche, Bernd Büchner, Thomas Mühl, and Gerald Gerlach J. Sens. Sens. Syst., 5, 245-259, doi:10.5194/jsss-5-245-2016, 2016 The presented work gives insight into the behaviour of co-resonantly coupled oscillating cantilever beams by means of electro-mechanical analogies. An electric circuit model is analysed with various stages of complexity, and conclusions are drawn regarding the applicability of the co-resonant concept for sensors. Furthermore, this is validated by a comparison between the theoretical predictions and experimental data.

Description: Hot-film and calorimetric thermal air flow sensors realized with printed board technology Thomas Glatzl, Samir Cerimovic, Harald Steiner, Almir Talic, Roman Beigelbeck, Artur Jachimowicz, Thilo Sauter, and Franz Keplinger J. Sens. Sens. Syst., 5, 283-291, doi:10.5194/jsss-5-283-2016, 2016 This paper addresses the development of flow sensors optimised for heating, ventilating, and air conditioning systems. The sensors are based on the printed circuit board technology facilitating robust, flexible (in terms of layout), and cost-effective devices. Two approaches for measuring fluid quantities are investigated in this context and several sensor embodiments were investigated and fabricated. After experimental characterisation, measurement and simulation results were compared.

Description: Use of VOC sensors for air quality control of building ventilation systems Journal of Sensors and Sensor Systems, 4, 159-168, 2015 Author(s): M. Großklos Air quality control with VOC (volatile organic compound) sensors in residential buildings could increase user comfort by adapting to the actual contaminant level. Preliminary tests assessed the dynamics of VOC levels in single-family passive houses with a ventilation system. At normal and exceptional usages, sufficient signal variations were measured for air quality control. An air quality control was developed and tested in four single-family passive house dwellings to control the building ventilation system via VOC sensors and a special adaptation algorithm to handle variable contaminant loads and sensor drift. Results showed good operation of the air quality control for the ventilation system, detecting changing contaminants within a few minutes and changing the air flow rate in the building immediately. The 43 VOC sensors used during the monitoring had more than 1.2 million working hours in total without any electrical failure, but with a loss of sensitivity for the calibration gas CO. The air quality control could manage that loss of sensitivity and worked well till the end of the field test. A comparison between VOC and CO 2 sensors in one building resulted in more detailed information about emission rates in the room with the VOC sensor, allowing one to get a better reaction of the ventilation system.

Description: An electrical characterisation system for the real-time acquisition of multiple independent sensing parameters from organic thin film transistors Journal of Sensors and Sensor Systems, 4, 169-177, 2015 Author(s): A. Dragoneas, L. Hague, and M. Grell The presence of multiple independent sensing parameters in a single device is the key conceptual advantage of sensor devices based on an organic thin film transistor (OTFT) over simple organic chemiresistors. Practically, however, these multiple parameters must first be extracted from the electrical characteristics of the OTFTs and, thus, they are not immediately apparent. To exploit the advantage of OTFT sensors, we require a measurement technology to extract these parameters in real time. Here, we introduce an efficient, cost-effective system that is a faster and more compact alternative to the expensive and cumbersome laboratory-based instruments currently available. The characterisation system presented here records the electric behaviour of OTFTs in the form of its "saturated transfer characteristics" multiple times per second for virtually unlimited periods of time, with the option to multiplex up to 20 devices in parallel. By applying a bespoke algorithm to the measured transfer characteristics, the system then extracts, in real time, several underlying transistor parameters (on- and off-current, threshold voltage, and charge carrier mobility). Tests were conducted on the example of a poly(thieno[3,2-b]thiophene) (PBTTT) OTFT exposed to ethanol vapour. The system extracts the underlying OTFT parameters with very low noise without introducing apparent correlations between independent parameters as an artefact.

Description: A programmable energy efficient readout chip for a multiparameter highly integrated implantable biosensor system M. Nawito, H. Richter, A. Stett, and J. N. Burghartz Adv. Radio Sci., 13, 103-108, doi:10.5194/ars-13-103-2015, 2015 In this work an Application Specific Integrated Circuit (ASIC) for an implantable electrochemical biosensor system is presented. The ASIC drives the measurement electrodes and performs amperometric measurements for determining the oxygen concentration, potentiometric measurements for evaluating the pH‐level as well as temperature measurements. The chip was fabricated and shows good result which conform to the Simulation data.

Description: Reflexionseigenschaften von Windenergieanlagen im Funkfeld von Funknavigations- und Radarsystemen S. Sandmann, S. Divanbeigi, and H. Garbe Adv. Radio Sci., 13, 9-18, doi:10.5194/ars-13-9-2015, 2015 Die hier behandelte Untersuchung befasst sich mit den Störungen des elektrischen Feldes einer Doppler Very High Frequency Omnidirectional Radio Range Navigationsanlage (DVOR) in der Gegenwart von Windenergieanlagen (WEA). Hierfür wird die Feldstärke auf 25 konzentrischen Kreisbahnen, sog. Orbit Flights verschiedener Höhen und mit verschiedenen Radien rund um die DVOR-Anlage numerisch simuliert. Insbesondere werden die Einflüsse diverser Parameter der WEA wie deren Anzahl, Position, Rotorwinkel, Turmhöhe und Rotordurchmesser auf die Feldverteilung herausgestellt, sowie die Anwendbarkeit der Simulationsmethode Physical Optics (PO) durch Vergleich der Simulationsergebnisse mit denen der Multi Level Fast Multipol Method (MLFMM) untersucht.

Description: Validation of the radiation pattern of the VHF MST radar MAARSY by scattering off a sounding rocket's payload T. Renkwitz, C. Schult, R. Latteck, and G. Stober Adv. Radio Sci., 13, 41-48, doi:10.5194/ars-13-41-2015, 2015 The Middle Atmosphere Alomar Radar System (MAARSY) is a monostatic radar with an active phased array antenna designed for studies of phenomena in the mesosphere and lower thermosphere. Its design, in particular the flexible beam forming and steering capability, makes it a powerful instrument to perform observations with high angular and temporal resolution. For the configuration and analysis of experiments carried out with the radar it is essential to have knowledge of the actual radiation pattern. Therefore, during the time since the radar was put into operation various active and passive experiments have been performed to gain knowledge of the radiation pattern. With these experiments the beam pointing accuracy, the beam width and phase distribution of the antenna array were investigated. Here, the use of a sounding rocket and its payload as a radar target is described which was launched in the proximity of the radar. The analysis of these observations allows the detailed investigation of the two-way radiation pattern for different antenna array sizes and beam pointing positions.

Description: Improving the range of UHF RFID transponders using solar energy harvesting under low light conditions A. Ascher, M. Lehner, M. Eberhardt, and E. Biebl Adv. Radio Sci., 13, 81-86, doi:10.5194/ars-13-81-2015, 2015 The sensitivity of passive UHF RFID transponders (Radio Frequency Identification) is the key issue, which determines the maximum read range of an UHF RFID system. During this work the ability of improving the sensitivity using solar energy harvesting, especially for low light conditions, is shown. To use the additional energy harvested from the examined silicon and organic solar cells, the passive RFID system is changed into a semi-active one. This needs no changes on the reader hardware itself, only the used RFIC (Radio Frequency Integrated Circuit) of the transponder has to possess an additional input pin for an external supply voltage. The silicon and organic cells are evaluated and compared to each other regarding their low light performance. The different cells are examined in a shielded box, which is protected from the environmental lighting. Additionally, a demonstrator is shown, which makes the measurement of the extended read range with respect to the lighting conditions possible. If the cells are completely darkened, the sensitivity gain is ascertained using high capacity super caps. Due to the measurements an enhancement in range up to 70 % could be guaranteed even under low light conditions.

Description: Spherical-multipole analysis of an arbitrarily directed complex-source beam diffracted by an acoustically soft or hard circular cone A. Reinhardt, H. Bruens, L. Klinkenbusch, M. Katsav, and E. Heyman Adv. Radio Sci., 13, 57-61, doi:10.5194/ars-13-57-2015, 2015 An arbitrarily directed complex-source beam (CSB) is diffracted by an acoustically soft or hard semi-infinite circular cone. The method can be used to probe any desired part of the cone inclduing its tip. The scattered field is isolated by subtracting the incident from the diffracted field and can be used to derive diffraction coefficients for improving asymptotic methods such as the GTD or the UTD.

Description: Efficient determination of the left-eigenvectors for the Method of Lines S. F. Helfert Adv. Radio Sci., 13, 19-29, doi:10.5194/ars-13-19-2015, 2015 To enforce the continuity of transverse electric and magnetic fields at boundaries, rectangular matrices containing the field distribution ('right eigenvectors') have to be inverted. This can be done with left eigenvectors. Here, it is shown how the latter ones can be determined with simple matrix products from previously determined right eigenvectors. For this purpose the relation between the transverse electric and magnetic fields known from Maxwell's equations is utilized.

Description: Potential of dynamic spectrum allocation in LTE macro networks H. Hoffmann, P. Ramachandra, I. Z. Kovács, L. Jorguseski, F. Gunnarsson, and T. Kürner Adv. Radio Sci., 13, 95-102, doi:10.5194/ars-13-95-2015, 2015 In recent years Mobile Network Operators (MNOs) worldwide are extensively deploying LTE networks in different spectrum bands and utilising different bandwidth configurations. Initially, the deployment is coverage oriented with macro cells using the lower LTE spectrum bands. As the offered traffic (i.e. the requested traffic from the users) increases the LTE deployment evolves with macro cells expanded with additional capacity boosting LTE carriers in higher frequency bands complemented with micro or small cells in traffic hotspot areas. For MNOs it is crucial to use the LTE spectrum assets, as well as the installed network infrastructure, in the most cost efficient way. The dynamic spectrum allocation (DSA) aims at (de)activating the available LTE frequency carriers according to the temporal and spatial traffic variations in order to increase the overall LTE system performance in terms of total network capacity by reducing the interference. This paper evaluates the DSA potential of achieving the envisaged performance improvement and identifying in which system and traffic conditions the DSA should be deployed. A self-optimised network (SON) DSA algorithm is also proposed and evaluated. The evaluations have been carried out in a hexagonal and a realistic site-specific urban macro layout assuming a central traffic hotspot area surrounded with an area of lower traffic with a total size of approximately 8 × 8 km 2 . The results show that up to 47 % and up to 40 % possible DSA gains are achievable with regards to the carried system load (i.e. used resources) for homogenous traffic distribution with hexagonal layout and for realistic site-specific urban macro layout, respectively. The SON DSA algorithm evaluation in a realistic site-specific urban macro cell deployment scenario including realistic non-uniform spatial traffic distribution shows insignificant cell throughput (i.e. served traffic) performance gains. Nevertheless, in the SON DSA investigations, a gain of up to 25 % has been observed when analysing the resource utilisation in the non-hotspot cells.

Description: An active UHF RFID localization system for fawn saving M. Eberhardt, M. Lehner, A. Ascher, M. Allwang, and E. M. Biebl Adv. Radio Sci., 13, 87-94, doi:10.5194/ars-13-87-2015, 2015 This paper presents a localization concept for fawn saving. Fawns can be saved during pasture mowing by marking them with an active UHF RFID transponder. The system consists of a mowing-machine mounted direction-of-arrival (DOA) system and a handheld DOA device. Only by estimating the DOA one can reliable localize the marked fawns. The whole RFID and DOA system is presented and communication concept is shown.

Description: Charge pump design in 130 nm SiGe BiCMOS technology for low-noise fractional-N PLLs M. Kucharski and F. Herzel Adv. Radio Sci., 13, 133-139, doi:10.5194/ars-13-133-2015, 2015 This paper presents a charge pump (CP) designed for a high linearity and a low noise to be used in a fractional-N phase-locked loop (PLL). An internal supply regulator with low intrinsic device noise is included in the design optimization. The high CP linearity is shown to reduce the level of in-band spurs in a fractional-N PLL tremendously.

Description: A test method for analysing disturbed ethernet data streams M. Kreitlow, F. Sabath, and H. Garbe Adv. Radio Sci., 13, 149-153, doi:10.5194/ars-13-149-2015, 2015 Ethernet connections can suffer from data corruption due to intentional electromagnetic interference. In this paper a software-based measuring method is presented, which allows a direct assessment of the effects on the link layer without an unwanted influence of software related effects on higher protocol layers. This gives a simple tool for a quantitative analysis of the disturbance of an Ethernet connection based on time domain data.

Description: Design investigation to improve voltage swing and bandwidth of the SiGe driver circuit for a silicon electro-optic ring modulator A. Fatemi, H. Gaul, U. Keil, and H. Klar Adv. Radio Sci., 13, 121-125, doi:10.5194/ars-13-121-2015, 2015 This paper reports on a new SiGe driver IC to address the low breakdown voltage level of modern BiCMOS transistors. An optical modulator driver IC in SiGe 250 nm technology with a supply voltage of 4.5 V is presented. This driver IC consists of pre- and main driver stages where a newly modified cascode topology and capacitance degeneration technique is employed to meet current application requirements; high voltage swing at high datarate.

Description: High-voltage circuits for power management on 65 nm CMOS S. Pashmineh and D. Killat Adv. Radio Sci., 13, 109-120, doi:10.5194/ars-13-109-2015, 2015 This paper presents two high-voltage circuits used in power management, a switching driver for buck converter with optimized on-resistance and a low dropout (LDO) voltage regulator with 2-stacked pMOS pass devices. The circuit design is based on stacked MOSFETs, thus the circuits are technology independent.

Description: Impedance spectra classification for determining the state of charge on a lithium iron phosphate cell using a support vector machine P. Jansen, D. Vergossen, D. Renner, W. John, and J. Götze Adv. Radio Sci., 13, 127-132, doi:10.5194/ars-13-127-2015, 2015 New method for determining the state of charge on lithium iron phosphate cells using frequency domain data.

Description: Comparison of electromagnetic solvers for antennas mounted on vehicles M. S. L. Mocker, S. Hipp, F. Spinnler, H. Tazi, and T. F. Eibert Adv. Radio Sci., 13, 49-55, doi:10.5194/ars-13-49-2015, 2015 An electromagnetic solver comparison for various use cases of antennas mounted on vehicles is presented. For this purpose, several modeling approaches, called transient, frequency and integral solver, including the features fast resonant method and autoregressive filter, offered by CST MWS, are investigated. The solvers and methods are compared for a roof antenna itself, a simplified vehicle, a roof including a panorama window and a combination of antenna and vehicle. With these examples, the influence of different materials, data formats and parameters such as size and complexity are investigated. Also, the necessary configurations for the mesh and the solvers are described.

Description: Ein Konzept für den energieeffizienten Betrieb von Mobilfunknetzen N. Bayer and D. von Hugo Adv. Radio Sci., 13, 63-72, doi:10.5194/ars-13-63-2015, 2015 Maßnahmen zur Senkung des Energieverbrauches im Mobilfunk wurden im Forschungsförderungsprojekt ComGreen untersucht. Ein an die tatsächliche Auslastung angepasster Betrieb des Funkzugangsnetzes, der durch intelligente dynamische Rekonfiguration unter Nutzung von Kontextinformation erreicht werden kann, ermöglicht Energieeinsparungen im Bereich von 25–40 %. Dies wird durch Ergebnisse von Computer-Simulationen und anhand von Messungen, die an einer Testinstallation durchgeführt wurden, belegt.

Description: Is model-order reduction viable for the broadband finite-element analysis of electrically large antenna arrays? O. Floch, A. Sommer, O. Farle, and R. Dyczij-Edlinger Adv. Radio Sci., 13, 31-39, doi:10.5194/ars-13-31-2015, 2015 Model-order reduction provides an efficient way of computing frequency sweeps for finite-element models, because the dimension of the reduced-order system depends on the complexity of the frequency response rather than the size of the original model. For electrically large domains, however, the applicability of such methods is unclear because the system response may be very complicated. This paper provides a numerical study of the effects of bandwidth, electrical size, and scan angle on the size and convergence of the ROM, by considering linear antenna arrays. A mathematical model is proposed and validated against numerical experiments.

Description: Definition and test of the electromagnetic immunity of UAS for first responders C. Adami, S. Chmel, M. Jöster, T. Pusch, and M. Suhrke Adv. Radio Sci., 13, 141-147, doi:10.5194/ars-13-141-2015, 2015 Recent technological developments considerably lowered the barrier for unmanned aerial systems (UAS) to be employed in a variety of usage scenarios, comprising live video transmission from otherwise inaccessible vantage points. As an example, in the French-German ANCHORS project several UAS guided by swarm intelligence provide aerial views and environmental data of a disaster site while deploying an ad-hoc communication network for first responders. Since being able to operate in harsh environmental conditions is a key feature, the immunity of the UAS against radio frequency (RF) exposure has been studied. Conventional Electromagnetic Compatibility (EMC) applied to commercial and industrial electronics is not sufficient since UAS are airborne and can as such move beyond the bounds within which RF exposure is usually limited by regulatory measures. Therefore, the EMC requirements have been complemented by a set of specific RF test frequencies and parameters where strong sources are expected to interfere in the example project test case of an inland port environment. While no essential malfunctions could be observed up to field strengths of 30 V m −1 , a sophisticated, more exhaustive approach for testing against potential sources of interference in key scenarios of UAS usage should be derived from our present findings.

Description: A micro-capacitive pressure sensor design and modelling Ali E. Kubba, Ahmed Hasson, Ammar I. Kubba, and Gregory Hall J. Sens. Sens. Syst., 5, 95-112, doi:10.5194/jsss-5-95-2016, 2016 This work presents a novel design of a low power high-temperature MEMS elliptical capacitive pressure sensor that can be utilized within wireless sensor systems, e.g. TPMS. Throughout numerical and analytical analysis, it was found that sensor sensitivity and temperature resistance could be increased if the diaphragm area has two symmetrical segments of chords parallel to the major axis removed, and if diaphragm deformation increases the separation distance between the sensing capacitor plates.

Description: High-speed camera-based measurement system for aeroacoustic investigations Johannes Gürtler, Daniel Haufe, Anita Schulz, Friedrich Bake, Lars Enghardt, Jürgen Czarske, and Andreas Fischer J. Sens. Sens. Syst., 5, 125-136, doi:10.5194/jsss-5-125-2016, 2016 The interaction of sound and flow enables an efficient noise damping. Understanding this aeroacoustic damping phenomenon requires simultaneous measurement of flow and sound fields. Using a high-speed CMOS camera, two-component flow velocity measurements are performed in a three-dimensional region of interest. The sensor system can simultaneously capture sound and turbulent flow velocity oscillations. The presented measurements reveal that the sound energy is transferred into flow energy.

Description: 〈b〉Radar target simulator with complex-valued delay line modeling based on standard radar components〈/b〉〈br〉 Andreas R. Diewald, Manuel Steins, and Simon Müller〈br〉 Adv. Radio Sci., 16, 203-213, https://doi.org/10.5194/ars-16-203-2018, 2018〈br〉 A concept of low-cost hardware for radar target simulation is presented. The theoretical foundations are derived and analyzed. An implementation of a demonstrator operating in the 24 GHz ISM band is shown for which the dynamical range simulation was implemented in a FPGA with fast sampling 10 ADCs and DACs. By using a FIR filtering approach a fine discretization of the range could be reached which will furthermore allow an inherent and automatic Doppler simulation by moving the target.

Description: 〈b〉Spectrum management and compatibility studies with Python〈/b〉〈br〉 Benjamin Winkel and Axel Jessner〈br〉 Adv. Radio Sci., 16, 177-194, https://doi.org/10.5194/ars-16-177-2018, 2018〈br〉 We developed the software "pycraf". It allows to analyse the compatibility between applications and services that make use of radio waves, for example mobile communications providers. The radio wave spectrum is very limited, which makes it important that devices do not interfere with each other. One major application of "pycraf" is to calculate protection criteria for radio astronomy observatories, which are extremely sensitive to man-made radio emission, potentially rendering them blind.

Description: 〈b〉Propagation of current waves along a transmission line with randomly located non-uniformities inside a rectangular resonator〈/b〉〈br〉 Sergey V. Tkachenko, Jürgen B. Nitsch, Moustafa Raya, Ronald Rambousky, and Ralf Vick〈br〉 Adv. Radio Sci., 16, 195-201, https://doi.org/10.5194/ars-16-195-2018, 2018〈br〉 In this paper, we investigate the propagation of high-frequency current waves along a stochastic transmission line inside a rectangular cavity using as basis the model of a transmission line with the symmetry of the resonator. The stochastization of the line is created by a stochastically arranged chain of loads. Using similar models one also can take into account stochastic geometry of the line.

Description: 〈b〉Task-specific uncertainty estimation for medical CT measurements〈/b〉〈br〉 Judith Bredemann and Robert H. Schmitt〈br〉 J. Sens. Sens. Syst., 7, 627-635, https://doi.org/10.5194/jsss-7-627-2018, 2018〈br〉 Computed tomography (CT) is an important imaging technology which enables minimally invasive procedures. Uncertainties in imaging lead to erroneous initial conditions for the navigation process during minimally invasive surgery and result in a higher risk of unintended injuries. To minimize the risk, the uncertainties of the imaging process need to be estimated and considered during the planning of a procedure. A method for estimating the uncertainty is demonstrated.

Description: 〈b〉Highly sensitive coulometric titration of oxygen for the characterization of solid materials at elevated temperatures〈/b〉〈br〉 Alexander Herms, Jingying Yao, Jens Zosel, Vladimir Vashook, Wolfram Oelßner, and Michael Mertig〈br〉 J. Sens. Sens. Syst., 7, 621-625, https://doi.org/10.5194/jsss-7-621-2018, 2018〈br〉 For the understanding of new materials, especially oxides, oxygen exchange of such materials and its consequences for their properties are of high interest. For this purpose a new setup for oxygen solid electrolyte coulometry with electrochemical cells made of yttria-stabilized zirconia (YSZ) is presented. It could be shown that this setup enables the measurement of exchanged oxygen from the picomol up to the higher nanomol range with a precision which was not achieved so far.

Description: Investigation of InAsSbP quantum dot mid-infrared sensors Journal of Sensors and Sensor Systems, 4, 249-253, 2015 Author(s): V. G. Harutyunyan, K. M. Gambaryan, V. M. Aroutiounian, and I. G. Harutyunyan This work presents the results of investigations of a low bias mid-infrared(IR) photoconductive cell (PCC) with InAsSbP quantum dots (QDs). The self-assembled nanostructures were grown on an InAs(100) substrate by modified liquid phase epitaxy. The coarsening of the QDs due to Ostwald ripening was discussed. Hysteresis with a remnant capacitance of 0.483 pF and contra-directional oscillations on the PCC's capacitance–voltage characteristic at 78 K were observed. Additionally, peaks at 3.48, 3.68 and 3.89 μm on the room temperature photoresponse spectrum of a quantum dot photoconductive cell were detected. Room temperature photo-sensing properties were investigated under an irradiation of 3.39 μm as well. At a power density of 0.07 W cm −2 , the surface resistance of quantum dot PCC was reduced by up to 7 %. A current responsivity of 0.2 mA W −1 was measured at an applied voltage of 8 mV.

Description: Hyperspectral imaging for monitoring oxygen saturation levels during normothermic kidney perfusion Florian Tetschke, Wenke Markgraf, Marian Gransow, Susanne Koch, Christine Thiele, Axel Kulcke, and Hagen Malberg J. Sens. Sens. Syst., 5, 313-318, doi:10.5194/jsss-5-313-2016, 2016 Hyperspectral imaging (HSI) has the potential to add a beneficial tool for the assessment of transplanted organs. Camera-based technologies such as HSI allow the fast and noninvasive monitoring of relevant physiological parameters. The correlation of HSI-based parameters with functional kidney parameters may be useful for the evaluation of the acceptability of marginal organs, thereby addressing the society-related problem of the shortage of available organs for transplantation.

Description: A novel approach for detecting HMDSO poisoning of metal oxide gas sensors and improving their stability by temperature cycled operation Journal of Sensors and Sensor Systems, 4, 305-311, 2015 Author(s): M. Schüler, T. Sauerwald, and A. Schütze In this paper we study the effect of hexamethyldisiloxane (HMDSO) vapor on an SnO 2 -based gas sensor (GGS 1330, UST Umweltsensortechnik GmbH, Geschwenda, Germany) in a temperature cycled operation (TCO). We show that HMDSO poisoning can be quantified at early stages (85 to 340 ppm × min) with a resolution of ±85 ppm × min using TCO. This novel approach for sensor self-monitoring provides a simple method for early detection of HMDSO poisoning. It is thereby possible to detect poisoning before the sensor function is strongly impaired. In this paper we show that by using an appropriate normalization of the sensor data, the stability of gas discrimination by linear discriminant analysis (LDA) can be improved, which in turn facilitates a more accurate determination of the poisoning state by a hierarchical LDA discrimination. For a specific temperature cycle and feature extraction approach, we show that identification of ethanol and carbon monoxide is still possible after poisoning with 900 ppm × min HMDSO, i.e. a HMDSO poisoning dose more than twice as high as required by DIN EN 50194-1.

Description: Determination of the material properties of polymers using laser-generated broadband ultrasound Leander Claes, Thorsten Meyer, Fabian Bause, Jens Rautenberg, and Bernd Henning J. Sens. Sens. Syst., 5, 187-196, doi:10.5194/jsss-5-187-2016, 2016 We present a non-destructive method to determine the material properties, for example elastic constants, of metal and polymer plates using laser-generated ultrasound. The ultrasonic signals are detected using an ultrasonic transducer that shows high sensitivity over a wide rage of frequencies. A method of signal processing to determine material properties is described and can be expanded upon to characterize more complex samples, such as fibre reinforced composites.

Description: Offset stable piezoresistive high-temperature pressure sensors based on silicon Robert Täschner, Erik Hiller, and Michael Blech J. Sens. Sens. Syst., 5, 197-203, doi:10.5194/jsss-5-197-2016, 2016 The exploitation of new application fields and the drive to size reduction even in highly stable pressure sensing systems makes the extension of the operating temperature range of the microelectromechanical sensors (MEMS) essential. For this reason, a silicon-based pressure sensor with an application temperature ranging up to 300 °C and the associated manufacturing technology was developed. The evolved sensor has an excellent stability and is uncomplicated to mount due to its stress insensitivity.

Description: Instrumented flow-following sensor particles with magnetic position detection and buoyancy control Sebastian Felix Reinecke and Uwe Hampel J. Sens. Sens. Syst., 5, 213-220, doi:10.5194/jsss-5-213-2016, 2016 Sensor particles with buoyancy control and position detection are presented, which are used for flow tracking in large vessels, such as biogas digesters and waste water tanks. They were tested in the realistic flows of a biogas digester. The buoyancy control allows taring for good flow tracing by the sensor particles, and it lets them float to the surface after data acquisition for easy recovery. The fluid mixing was estimated from detected passages of sensor particles at a magnetic coil.

Description: First steps to develop a sensor for a Tian–Calvet calorimeter with increased sensitivity Franz Schubert, Michael Gollner, Jaroslaw Kita, Florian Linseis, and Ralf Moos J. Sens. Sens. Syst., 5, 205-212, doi:10.5194/jsss-5-205-2016, 2016 Initial steps to apply a new ceramic multi-layer sensor for a Tian–Calvet calorimeter are shown. The FEM-developed sensor consists of stacked ceramic discs and insulation rings. The functionality of the sensor disc was proven up to 600 °C and the entire stack was tested at room temperature. The resolution was 5 µW and the sensitivity was 8.5 µV mW −1 . The new sensor shows similar specifications as commercial devices and presents a good starting point for future high temperature applications.

Description: Highly selective solid electrolyte sensor for the analysis of gaseous mixtures Matthias Schelter, Jens Zosel, Wolfram Oelßner, Ulrich Guth, and Michael Mertig J. Sens. Sens. Syst., 5, 319-324, doi:10.5194/jsss-5-319-2016, 2016 The operation principle of a commercially available solid electrolyte sensor was modified with respect to applications in flowing gaseous mixtures containing H 2 and O 2 . For this purpose the generally applied coulometric or potentiometric operation mode was replaced by cyclic voltammetry. By varying the sensor temperature, electrode area and potential scan rate, the conditions for the characteristic peak formation for every gas component were determined. While hydrogen oxidation peaks arise at potential scan rates up to 100 mV s −1 , oxygen reduction peaks develop between 200 and 1000 mV s −1 . A linear relationship between peak area/peak height and concentration was found at concentrations ϕ  (H 2 ) 〈 100 vol. ppm and ϕ  (O 2 ) ≤ 500 vol. ppm. It could be demonstrated that hydrogen can be measured selectively at catalytically highly active Pt electrodes even in gas mixtures with comparably high oxygen concentrations by using cyclic voltammetry.

Description: Design, characterization, and modeling of microcirculation systems with integrated oxygenators Mathias Busek, Stefan Gruenzner, Tobias Steege, Florian Schmieder, Udo Klotzbach, and Frank Sonntag J. Sens. Sens. Syst., 5, 221-228, doi:10.5194/jsss-5-221-2016, 2016 A novel cell-cultivation platform with small circulating volume and included oxygen controlling system is presented. This system may be used to investigate the influence of oxygen restriction, called hypoxia, to cultivated human cells and therefore helps to reduce animal testing in this field of research. Furthermore, a mathematic model of the oxygen transport is presented which may be utilized to produce well-defined oxygen microenvironments.

Description: Modelling of the response of acoustic piezoelectric resonators in biosensor applications – Part 1: The general theoretical analysis Journal of Sensors and Sensor Systems, 4, 137-142, 2015 Author(s): M. V. Voinova Acoustic piezoelectric resonators are widely used as precise analytical chemistry tools for the real-time monitoring of a negligibly small amount of surface-attached mass of biological components, in particular, in environmental biosensor measurements. The surface acoustic wave (SAW)-based sensors and the quartz crystal microbalance (QCM) compared in our work belong to the leading group due to their considerable advantages. These piezoelectric resonators are considered now as high-resolution analytical tools allowing researchers to discriminate between components due to the selective polymer coating on the resonator surface. The gravimetrical measurements performed with the SAW-based or QCM sensors provide the experimental data with high precision for the detection of surface mass for the thin adsorbed layer rigidly attached to the oscillator surface. The new challenge is the analysis of soft and biological materials, where the viscous losses of energy can essentially influence measured characteristics. Modelling is the important part of the analysis allowing researchers to quantify the results of the experiments. The present work provides a general theory of SH-SAW devices probing soft and biological materials. The results are compared with QCM-D operated in liquid media.

Description: Is it possible to detect in situ the sulfur loading of a fixed bed catalysts with a sensor? Journal of Sensors and Sensor Systems, 4, 143-149, 2015 Author(s): P. Fremerey, A. Jess, and R. Moos This study reports on a sensor concept to measure in situ sulfur poisoning (sulfidation) of refinery catalysts, in this case, of commercial silica pellets loaded with highly dispersed nickel. Catalyst pellets were poisoned in diluted H 2 S between 100 and 400 °C and the sulfidation of the catalyst was observed. During this process, nickel sulfides are formed on the catalyst according to X-ray diffraction spectra and energy dispersive X-ray spectroscopy data. The sulfidation kinetics was quantitatively described by a shrinking core model. Representative catalyst pellets were electrically contacted, and their impedance was recorded in situ during sulfidation. At the beginning, the particles are highly insulating and behave capacitively. Their conductivity increases by decades during sulfidation. At high temperatures, an almost constant slope in the double-logarithmic representation vs. time can be found. At low temperatures, the conductivity remains constantly low for a long time but changes then rapidly by decades, which is also indicated by the phase that drops from capacitive to ohmic behavior. Since nickel sulfides exhibit a lower conductivity than nickel, the conductivity increase by decades during sulfidation can only be explained by electrically conducting percolation paths that form during sulfidation. They originate from the increased volume of sulfides compared to the pure nickel metal.

Description: Micro-structured electron accelerator for the mobile gas ionization sensor technology Journal of Sensors and Sensor Systems, 4, 151-157, 2015 Author(s): C. M. Zimmer, K. T. Kallis, and F. J. Giebel Mobile and economically priced gas monitoring and warning systems will become increasingly important for civil security, such as in fire brigade operations in undefined hazardous environments (Daum et al., 2006). Normally, photoionization detectors (PIDs) are used for the detection of gases. Hereby, the principle is based upon the ionization of the measured gas by photons, which are generated by a high-energetic gas discharge lamp with energy of 10–11 eV. Besides the detrimental unspecific gas detection because of the ionization of all gases with ionization potential (IP) below the provided photon energy, sensors also have a short lifetime combined with a high cost ( http://www.intlsensor.com/pdf/photoionization.pdf ). This can be remedied by the concept of an electronic supported photoionization detector (ePID; Zimmer et al., 2012) consisting of a durable UV-LED with an above-positioned electron accelerator chip manufactured on a glass substrate by planar technology. Photoelectrons are extracted by UV illumination out of the bottom electrode and will be accelerated to an energy matching the ionization potential of the gas by a downstream acceleration grid. Thereby, the stable honeycomb-structured grid acts as a porous separator between the evacuated electron acceleration path due to nm scaling and the ionization area of the detector. To enhance the emitting area yielding a higher photoelectron current, the grid structure almost levitates, realized by the use of compatible planar technological processes such as reactive ion etching (RIE) and isotropic wet etching of sacrificial layers, which will be explained in detail in this paper. Furthermore, the tunability of the grid's acceleration voltage would enable a substance-specific determination of the gas composition, where the ionization of the analytes is clearly performed by photoelectrons instead of photons.

Description: Novel microthermal sensor principle for determining the mixture ratio of binary fluid mixtures using Föppl vortices Journal of Sensors and Sensor Systems, 4, 239-247, 2015 Author(s): B. Schmitt, C. Kiefer, and A. Schütze A novel sensor principle for determining binary fluid mixtures of known components is presented, making use of different thermal and rheological properties of the mixture's components. Using a microheater, a heat pulse is introduced in the mixture. The resulting temperature increase depends on the thermal properties of the mixture, allowing determination of the mixture ratio. Placing a bluff body in the fluid channel causes the formation of a stationary pair of vortices behind the body. The length of the vortex pair depends on the mixture's viscosity and thus its composition. By placing the microheater in the vortex area and making use of forced convection which changes with the size of the vortex, the sensitivity for determination of the mixture ratio can be increased by a factor of 2.5 compared to the direct thermal measurement. The flow velocity is measured independently of the mixture ratio using time-of-flight thermal anemometry.

Description: Magnetic noise contribution of the ferromagnetic core of induction magnetometers Journal of Sensors and Sensor Systems, 4, 229-237, 2015 Author(s): C. Coillot, M. El Moussalim, E. Brun, A. Rhouni, R. Lebourgeois, G. Sou, and M. Mansour The performance of induction magnetometers, in terms of resolution, depends both on the induction sensor and the electronic circuit. To investigate accurately the sensor noise sources, an induction sensor, made of a ferrite ferromagnetic core, is combined with a dedicated low voltage and current noise preamplifier, designed in CMOS 0.35 μm technology. A modelling of the contribution of the ferromagnetic core to the noise through the complex permeability formalism is performed. Its comparison with experimental measurements highlight another possible source for the dominating noise near the resonance.

Description: Micro- and nanocoordinate measurements of micro-parts with 3-D tunnelling current probing Journal of Sensors and Sensor Systems, 4, 199-208, 2015 Author(s): A. Schuler, T. Hausotte, and Z. Sun Measurement tasks of modern micro- and nanometrology are posing a problem for current measurement instruments with decreasing structure sizes and rising aspect ratios. There is an open requirement for nanometre-resolving 3-D capable sensors and corresponding 3-D positioning systems to operate the sensors for 3-D measurements. A 3-D probing system based on electrical interaction is presented which is operated on a nanopositioning system type SIOS NMM-1. Furthermore, we demonstrate the progress and new possibilities for 3-D measurements with the nanopositioning and nanomeasurement machine NMM-1 and also with the application of a rotary kinematic chain. In addition new 3-D measurement routines for the NMM-1, also for micro-tactile probing systems as well as current plans, are shown.

Description: Calibration of uncooled thermal infrared cameras Journal of Sensors and Sensor Systems, 4, 187-197, 2015 Author(s): H. Budzier and G. Gerlach The calibration of uncooled thermal infrared (IR) cameras to absolute temperature measurement is a time-consuming, complicated process that significantly influences the cost of an IR camera. Temperature-measuring IR cameras display a temperature value for each pixel in the thermal image. Calibration is used to calculate a temperature-proportional output signal (IR or thermal image) from the measurement signal (raw image) taking into account all technical and physical properties of the IR camera. The paper will discuss the mathematical and physical principles of calibration, which are based on radiometric camera models. The individual stages of calibration will be presented. After start-up of the IR camera, the non-uniformity of the pixels is first corrected. This is done with a simple two-point correction. If the microbolometer array is not temperature-stabilized, then, in the next step the temperature dependence of the sensor parameters must be corrected. Ambient temperature changes are compensated for by the shutter correction. The final stage involves radiometric calibration, which establishes the relationship between pixel signal and target object temperature. Not all pixels of a microbolometer array are functional. There are also a number of defective, so-called "dead" pixels. The discovery of defective pixels is a multistep process that is carried out after each stage of the calibration process.

Description: Refractive index sensing of gases based on a one-dimensional photonic crystal nanocavity Journal of Sensors and Sensor Systems, 4, 209-215, 2015 Author(s): M. Mohebbi Silicon photonic crystal sensors have become very attractive for various optical sensing applications. Using silicon as a material platform provides the ability to fabricate sensors with other photonic devices on a single chip. In this paper, a new optical sensor based on optical resonance in a one-dimensional silicon photonic crystal with an air defect is theoretically studied for refractive index sensing in the infrared wavelength region. The air defect introduces a cavity into the photonic crystal, making it suitable for probing the properties of a gas found within the cavity. This photonic crystal nanocavity is designed to oscillate at a single mode with a high quality factor, allowing for refractive index sensing of gases with a high sensitivity. A method is presented to maximize the sensitivity of the sensor and to obtain a very narrow bandwidth cavity mode for good sensor resolution. We change the thickness of the air layers linearly in the photonic crystals on both sides of the nanocavity and show that a sensitivity of 1200 nm RIU −1 can be achieved. We present a detailed analysis of the sensor and variations of the layer thicknesses, the cavity length, and the number of periodic layers in the photonic crystal are investigated. This optical sensor has a much simpler design and higher sensitivity compared to other photonic crystal sensors reported previously.

Description: Investigations into packaging technology for membrane-based thermal flow sensors Journal of Sensors and Sensor Systems, 4, 45-52, 2015 Author(s): G. Dumstorff, E. Brauns, and W. Lang A new packaging method to mount a membrane-based thermal flow sensor, flush with the surface, is presented. Therefore, a specific design for the housing is shown, which is also adaptable to other conditions. It has been experimentally shown that it is important to mount the sensor flush with the surface. In addition, the experimental results are discussed. If a membrane-based thermal flow sensor is not mounted flush with the surface, vortices can occur (depending on velocity and fluid properties) or the reduction in the channel cross section plus a decrease in sensitivity have to be taken into account.

Description: Alternative strategy for manufacturing of all-solid-state reference electrodes for potentiometry Journal of Sensors and Sensor Systems, 4, 53-61, 2015 Author(s): J. C. B. Fernandes and E. V. Heinke This paper presents an alternative strategy for manufacturing solid-state reference electrodes based on particles of graphite/silver/silver chloride synthesized by electroless deposition of metallic silver and silver chloride on graphite powder. Two kinds of reference electrodes were manufactured by mixing these particles with epoxy resin and hardener: quasi-reference and all-solid-state containing salts of alkaline or alkaline earth metals. All-solid-state reference electrodes can be sterilized with high-pressure saturated steam at 394.15 K (121 °C) using an autoclave. These electrodes presented a stable potential between pH 2 and 11. The electrode surface was characterized by scanning electron microscopy and showed the presence of silver and salt particles. The size of the silver particles was less than 2.5 μm. We successfully applied the all-solid state reference electrodes in potentiometric cells to measure pH and potassium ions in complex matrix by direct potentiometry and L-ascorbic acid by potentiometric titration.

Description: Monitoring human serum albumin cell cultures using surface plasmon resonance (SPR) spectroscopy Journal of Sensors and Sensor Systems, 4, 77-83, 2015 Author(s): A. Henseleit, C. Pohl, Th. Bley, and E. Boschke Continuously monitoring cell cultures is essential for both controlling critical parameters and improving understanding of key processes. An ideal technique in this context is surface plasmon resonance (SPR) spectroscopy, which essentially exploits changes in the angle of incident light that occur when molecules bind to a surface. It provides the ability to monitor real-time changes in small concentrations of various molecules, with no need for additional labels or sample preparation. Here we present an SPR-based immunoassay for monitoring concentrations of human serum albumin (HSA), and compare its sensitivity when used in conjunction with a Biacore platform and the cheaper, smaller li SPR system. In conjunction with either system, the immunoassay can detect HSA (a hepatocyte viability marker) at concentrations typically present in three-dimensional hepatocyte cultures mimicking the liver used to evaluate effects of drug candidates before exposure to humans or animals. Furthermore, in conjunction with the li SPR system, it is sufficiently sensitive to measure the much lower HSA levels present in skin–hepatocyte co-cultures.

Description: Lab-on-Spoon – a 3-D integrated hand-held multi-sensor system for low-cost food quality, safety, and processing monitoring in assisted-living systems Journal of Sensors and Sensor Systems, 4, 63-75, 2015 Author(s): A. König and K. Thongpull Distributed integrated sensory systems enjoy increasing impact leveraged by the surging advance of sensor, communication, and integration technology in, e.g., the Internet of Things, cyber-physical systems, Industry 4.0, and ambient intelligence/assisted-living applications. Smart kitchens and "white goods" in general have become an active field of R&D. The goal of our research is to provide assistance for unskilled or challenged consumers by efficient sensory feedback or context on ingredient quality and cooking step results, which explicitly includes decay and contamination detection. As one front end of such a culinary-assistance system, an integrated, multi-sensor, low-cost, autonomous, smart spoon device, denoted as Lab-on-Spoon (LoS), has been conceived. The first realized instance presented here features temperature, color, and impedance spectroscopy sensing in a 3-D-printed spoon package. Acquired LoS data are subject to sensor fusion and decision making on the host system. LoS was successfully applied to liquid ingredient recognition and quality assessment, including contamination detection, in several applications, e.g., for glycerol detection in wine. In future work, improvement to sensors, electronics, and algorithms will be pursued to achieve an even more robust, dependable and self-sufficient LoS system.

Description: Luminescent determination of nitrite traces in water solutions using cellulose as sorbent Journal of Sensors and Sensor Systems, 4, 31-36, 2015 Author(s): S. G. Nedilko, S. L. Revo, V. P. Chornii, V. P. Scherbatskyi, and M. S. Nedielko Morphology and photoluminescence (PL) properties for microcrystalline cellulose (MCC), microcrystalline nitrite powders of common formulae MNO 2 (M = Na, K) (MCN) and two-component materials composed of both MCC and MCN have been prepared and characterized by means of optical microscopy and luminescence spectroscopy. This study aimed to clarify a possibility of low-limit determination of the nitrite traces in water solutions by luminescent method.

Description: Defects and gas sensing properties of carbon nanotube-based devices Journal of Sensors and Sensor Systems, 4, 25-30, 2015 Author(s): S. Baldo, V. Scuderi, L. Tripodi, A. La Magna, S.G. Leonardi, N. Donato, G. Neri, S. Filice, and S. Scalese In this work we report on the development of back-gated carbon nanotube-field effect transistors (CNT-FETs), with CNT layers playing the role of the channel, and on their electrical characterisation for sensing applications. The CNTs have been deposited by electrophoresis on an interdigitated electrode region created on a SiO 2 /Si substrate. Different kinds of CNTs have been used (MWCNTs by arc discharge in liquid nitrogen and MWCNTs by chemical vapour deposition, CVD) and the electrical characterisation of the devices was performed in a NH 3 - and NO 2 -controlled environment. Preliminary data have shown an increase in the channel resistance under NH 3 exposure, whereas a decrease is observed after exposure to NO 2 , and the sensitivity to each gas depends on the kind of CNTs used for the device. Furthermore, the defect formation by Si ion implantation on CNTs was investigated by high-resolution transmission electron microscopy (TEM) and Raman analysis. The behaviour observed for the different devices can be explained in terms of the interaction between structural or chemical defects in CNTs and the gas molecules.

Description: Piezoelectric transceiver matching for multiple frequencies Journal of Sensors and Sensor Systems, 4, 9-16, 2015 Author(s): A. Ens and L. M. Reindl Robust data transmission over long ranges with standard ultrasound devices is a challenge. Ultrasound indoor positioning systems in particular require long ranges and a robust data communication link. Fundamentally, a piezoelectric transducer has a narrow bandwidth for high sound pressure level and efficiency and is not suitable for broad-band applications. Moreover, ultrasound attenuation in the air increases quadratically within frequency, and thus ultrasound localization systems are restricted to low frequencies and low bandwidths. This work presents a novel method to match a piezoelectric transceiver for multiple frequencies by using the parallel and the series resonance of the transceiver. The aim is to adjust the amplitudes at different frequencies from different senders to the same level, which is important for orthogonal frequency division multiplex communication systems. Hence, an analog-to-digital converter (ADC) with low dynamic range (low voltage resolution) can be used to measure multiple frequencies with the same resolution. As a result, the optimization decreases the required dynamic range by 6 dB. Consequently, the ADC requires 1 bit fewer to ensure the same resolution for all carrier frequencies.

Description: Aerosol-assisted CVD synthesis, characterisation and gas-sensing application of gold-functionalised tungsten oxide Journal of Sensors and Sensor Systems, 3, 325-330, 2014 Author(s): F. Di Maggio, M. Ling, A. Tsang, J. Covington, J. Saffell, and C. Blackman Tungsten oxide nanoneedles (NNs) functionalised with gold nanoparticles (NPs) have been integrated with alumina gas-sensor platforms using a simple and effective co-deposition method via aerosol-assisted chemical vapour deposition (AACVD) utilising a novel gold precursor, (NH 4 )AuCl 4 . The gas-sensing results show that gold NP functionalisation of tungsten oxide NNs improves the sensitivity of response to ethanol, with sensitivity increasing and response time decreasing with increasing amount of gold.

Description: Objectifying user attention and emotion evoked by relevant perceived product components Journal of Sensors and Sensor Systems, 3, 315-324, 2014 Author(s): R. Schmitt, M. Köhler, J. V. Durá, and J. Diaz-Pineda A company's aim is to develop products that engage user attention and evoke positive emotions. Customers base their emotional evaluation on product components that are relevant for their perception. This paper presents findings of both identifying relevant product components and measuring emotions evoked by relevant perceived product components. To validate results, the comparison with self-reporting methods identifies similarities and differences between explicit expressed and implicit recorded customer requirements. On the one hand, eye tracking is applied to deduce the attention provoked by perceived product components. In order to link the product strategy with product components, the paper presents results considering the fact that the gaze track is affected by current thoughts. (Köhler et al., 2013, 2014a, b; Köhler and Schmitt, 2012) On the other hand, since self-reporting tools are only useful for obtaining information about the conscious part of customers' emotions, there is a need for measurement methods that measure the changes in physiological signals (bio-signals). Arousal is similar to emotional intensity and is related to the galvanic skin response. Positive or negative emotions are defined by the valence that is measured by facial electromyography. Findings are presented that relate changes in bio-signals on the aesthetical design to the global product impression as well as to emotions and, subsequently, linking changes in physiological signals to the evaluation of semantic concepts and design parameters. The presented approach provides conclusions and valid information about products as well as product components that provoke certain emotions and about product components linked to a certain product concept, which could be part of a product strategy. Consequently, hard facts and special design rules for emotional product design can be deduced.

Description: Challenges for Wireless Mesh Networks to provide reliable carrier-grade services Advances in Radio Science, 9, 377-382, 2011 Author(s): D. von Hugo and N. Bayer Provision of mobile and wireless services today within a competitive environment and driven by a huge amount of steadily emerging new services and applications is both challenge and chance for radio network operators. Deployment and operation of an infrastructure for mobile and wireless broadband connectivity generally requires planning effort and large investments. A promising approach to reduce expenses for radio access networking is offered by Wireless Mesh Networks (WMNs). Here traditional dedicated backhaul connections to each access point are replaced by wireless multi-hop links between neighbouring access nodes and few gateways to the backbone employing standard radio technology. Such a solution provides at the same time high flexibility in both deployment and the amount of offered capacity and shall reduce overall expenses. On the other hand currently available mesh solutions do not provide carrier grade service quality and reliability and often fail to cope with high traffic load. EU project CARMEN (CARrier grade MEsh Networks) was initiated to incorporate different heterogeneous technologies and new protocols to allow for reliable transmission over "best effort" radio channels, to support a reliable mobility and network management, self-configuration and dynamic resource usage, and thus to offer a permanent or temporary broadband access at high cost efficiency. The contribution provides an overview on preliminary project results with focus on main technical challenges from a research and implementation point of view. Especially impact of mesh topology on the overall system performance in terms of throughput and connection reliability and aspects of a dedicated hybrid mobility management solution will be discussed.

Description: Meteor radar measurements of mean winds and tides over Collm (51.3° N, 13° E) and comparison with LF drift measurements 2005–2007 Advances in Radio Science, 9, 335-341, 2011 Author(s): C. Jacobi An all-sky VHF meteor radar (MR) has been continuously operated at Collm (51.3° N, 13° E) since summer 2004. The radar measures meteor parameters, diffusion coefficients, and horizontal winds in the mesopause region. There exists a temporal overlap of the MR wind measurements with co-located low-frequency (LF) ionospheric drift measurements until 2007. Comparison of MR and LF semidiurnal tidal phases allows to empirically determine the virtual height overestimation of LF reflection heights due to the group retardation of LF waves. LF reference heights have to be reduced by up to 20 km to match real heights. Correction of LF heights for group retardation allows to determine the wind underestimation by the LF method compared with meteor radar measurements and opens the possibility to continue long-term trend analysis using mesosphere/lower thermosphere winds.

Description: IP-based mobility management for heterogeneous wireless access Advances in Radio Science, 10, 319-325, 2012 Author(s): H. J. Einsiedler and D. von Hugo Future high quality communication services will be offered in an integrated or converged network infrastructure maintaining both fixed wireless and mobile access via multi-mode user terminals. A support of various scenarios of user and/or terminal mobility within a common IP-based infrastructure requires intelligently designed control protocols. A major challenge is to provide seamless (i.e. lossless and low delay) handover between different radio cells and operator domains to enable continuation of unicast and multicast sessions while using network resources most efficiently. IETF (Internet Engineering Task Force) is specifying related IP mobility management protocols to be applicable also to a flat architecture as envisaged by Next Generation (Mobile) Networks (NGNs/NGMNs). The contribution will describe operator requirements towards such an approach. Both single-domain and multi-domain scenarios will be discussed based on federation ideas. Already existing solutions are taken into consideration and application of solution proposals towards a Distributed Mobility Management (DMM) currently under evaluation within IETF will be outlined.

Description: STF Optimierung von single-bit CT ΣΔ Modulatoren basierend auf skalierten Filterkoeffizienten Advances in Radio Science, 10, 313-317, 2012 Author(s): C. Widemann, C. Zorn, T. Brückner, M. Ortmanns, and W. Mathis Die vorliegende Arbeit beschäftigt sich mit dem Signalübertragungsverhalten von single-bit continuous-time (CT) ΣΔ Modulatoren. Dabei liegt der Fokus der Untersuchung auf dem Peaking der Signaltransferfunktion (STF). Dieser Effekt kann die Performance und die Stabilität des Gesamtsystems negativ beeinflussen, da bei auftretendem STF-Peaking Signale außerhalb des Signalbands verstärkt werden. In dieser Arbeit wird ein neuer Ansatz zur Reduktion des Peakings vorgestellt, der auf der Optimierung der Systemdynamik basiert. Dabei werden die Filterkoeffizienten des Modulators systematisch angepasst. Anhand eines Beispielsystems wird gezeigt, dass der Ansatz genutzt werden kann, um das Übertragungsverhalten des Modulators abhängig vom Ausgangssystem zu verändern. So kann entweder die Systemsperformance verbessert werden, ohne Peaking in der STF zu erzeugen, oder das STF-Peaking reduziert werden, ohne die Systemperformance stark zu beeinflussen.

Description: Differential Algebraic Equations of MOS Circuits and Jump Behavior Advances in Radio Science, 10, 327-332, 2012 Author(s): P. Sarangapani, T. Thiessen, and W. Mathis Many nonlinear electronic circuits showing fast switching behavior exhibit jump effects which occurs when the state space of the electronic system contains a fold. This leads to difficulties during the simulation of these systems with standard circuit simulators. A method to overcome these problems is by regularization, where parasitic inductors and capacitors are added at the suitable locations. However, the transient solution will not be reliable if this regularization is not done in accordance with Tikhonov's Theorem. A geometric approach is taken to overcome these problems by explicitly computing the state space and jump points of the circuit. Until now, work has been done in analyzing example circuits exhibiting this behavior for BJT transistors. In this work we apply these methods to MOS circuits (Schmitt trigger, flip flop and multivibrator) and present the numerical results. To analyze the circuits we use the EKV drain current model as equivalent circuit model for the MOS transistors.

Description: Development of a highly sensitive spectral camera for cartilage monitoring using fluorescence spectroscopy Journal of Sensors and Sensor Systems, 4, 289-294, 2015 Author(s): A. Kuehn, A. Graf, U. Wenzel, S. Princz, H. Mantz, and M. Hessling The Ulm University Medical Center and the Ulm University of Applied Sciences are developing a bioreactor to grow facial cartilage using the methods of tissue engineering. To ensure a sufficient quality of the cartilage prior to implantation, the cartilage growth has to be monitored continuously. Current cartilage analysis methods are destructive so that analysed cartilage sample is no longer suitable for implantation. Alternatively, it seems feasible to analyse cartilage during the cultivation process and before implantation using fluorescence spectroscopy after UV light excitation. This approach is non-invasive and allows an evaluation of the cartilage in terms of composition and quality. Cultured cartilage implants can reach sizes of several square centimetres and therefore it is necessary to examine it over its entire area. For recording fluorescence spectra of different spots of the cartilage sample, a highly sensitive spectral camera is being developed in two steps. The first step is a one-dimensional spectral camera that is able to record fluorescence spectra along a sample line. The second step enables the detection of spectra over the required two-dimensional sample area. This approach is based on computed tomography imaging spectrometry (CTIS) and allows non-invasive distinguishing of the most important cartilage compounds collagen I and collagen II.

Description: Shutter-less calibration of uncooled infrared cameras A. Tempelhahn, H. Budzier, V. Krause, and G. Gerlach J. Sens. Sens. Syst., 5, 9-16, doi:10.5194/jsss-5-9-2016, 2016 Infrared cameras based on microbolometer focal plane arrays (FPAs) are the most widely used cameras in thermography. For acceptable measurement uncertainty values, the disturbing influences of changing ambient temperature have to be considered. We propose a TEC-less and shutter-less correction approach based on additional temperature measurements inside the IR camera. The effects on the pixel responsivity and offset voltage are considered separately.

Description: Atmospheric transmission coefficient modelling in the infrared for thermovision measurements W. Minkina and D. Klecha J. Sens. Sens. Syst., 5, 17-23, doi:10.5194/jsss-5-17-2016, 2016 The aim of this paper is to discuss different models that describe atmospheric transmission in the infrared. They were compared in order to choose the most appropriate one for certain atmospheric conditions. Universal models and different inaccuracies connected with them were analysed in this paper. There have been models analysed from the literature, and these are used in infrared cameras.

Description: Qualification concept for optical multi-scale multi-sensor systems A. Loderer and T. Hausotte J. Sens. Sens. Syst., 5, 1-8, doi:10.5194/jsss-5-1-2016, 2016 This article describes a new qualification concept for dimensional measurements on optical measuring systems, using the example of a prototypical multi-scale multi-sensor fringe projection system for production-related inspections of sheet-bulk metal-formed parts. A new concept is developed for determining the orientations and positions of the sensors' measuring ranges in a common coordinate system. The principle element of the concept is a newly developed flexible reference artefact.

Description: Is model-order reduction viable for the broadband finite-element analysis of electrically large antenna arrays? O. Floch, A. Sommer, O. Farle, and R. Dyczij-Edlinger Adv. Radio Sci., 13, 31-39, doi:10.5194/ars-13-31-2015, 2015 Model-order reduction provides an efficient way of computing frequency sweeps for finite-element models, because the dimension of the reduced-order system depends on the complexity of the frequency response rather than the size of the original model. For electrically large domains, however, the applicability of such methods is unclear because the system response may be very complicated. This paper provides a numerical study of the effects of bandwidth, electrical size, and scan angle on the size and convergence of the ROM, by considering linear antenna arrays. A mathematical model is proposed and validated against numerical experiments.

Description: Ein Konzept für den energieeffizienten Betrieb von Mobilfunknetzen N. Bayer and D. von Hugo Adv. Radio Sci., 13, 63-72, doi:10.5194/ars-13-63-2015, 2015 Maßnahmen zur Senkung des Energieverbrauches im Mobilfunk wurden im Forschungsförderungsprojekt ComGreen untersucht. Ein an die tatsächliche Auslastung angepasster Betrieb des Funkzugangsnetzes, der durch intelligente dynamische Rekonfiguration unter Nutzung von Kontextinformation erreicht werden kann, ermöglicht Energieeinsparungen im Bereich von 25–40 %. Dies wird durch Ergebnisse von Computer-Simulationen und anhand von Messungen, die an einer Testinstallation durchgeführt wurden, belegt.

Description: Improving the range of UHF RFID transponders using solar energy harvesting under low light conditions A. Ascher, M. Lehner, M. Eberhardt, and E. Biebl Adv. Radio Sci., 13, 81-86, doi:10.5194/ars-13-81-2015, 2015 The sensitivity of passive UHF RFID transponders (Radio Frequency Identification) is the key issue, which determines the maximum read range of an UHF RFID system. During this work the ability of improving the sensitivity using solar energy harvesting, especially for low light conditions, is shown. To use the additional energy harvested from the examined silicon and organic solar cells, the passive RFID system is changed into a semi-active one. This needs no changes on the reader hardware itself, only the used RFIC (Radio Frequency Integrated Circuit) of the transponder has to possess an additional input pin for an external supply voltage. The silicon and organic cells are evaluated and compared to each other regarding their low light performance. The different cells are examined in a shielded box, which is protected from the environmental lighting. Additionally, a demonstrator is shown, which makes the measurement of the extended read range with respect to the lighting conditions possible. If the cells are completely darkened, the sensitivity gain is ascertained using high capacity super caps. Due to the measurements an enhancement in range up to 70 % could be guaranteed even under low light conditions.

Description: Spherical-multipole analysis of an arbitrarily directed complex-source beam diffracted by an acoustically soft or hard circular cone A. Reinhardt, H. Bruens, L. Klinkenbusch, M. Katsav, and E. Heyman Adv. Radio Sci., 13, 57-61, doi:10.5194/ars-13-57-2015, 2015 An arbitrarily directed complex-source beam (CSB) is diffracted by an acoustically soft or hard semi-infinite circular cone. The method can be used to probe any desired part of the cone inclduing its tip. The scattered field is isolated by subtracting the incident from the diffracted field and can be used to derive diffraction coefficients for improving asymptotic methods such as the GTD or the UTD.

Description: Potential of dynamic spectrum allocation in LTE macro networks H. Hoffmann, P. Ramachandra, I. Z. Kovács, L. Jorguseski, F. Gunnarsson, and T. Kürner Adv. Radio Sci., 13, 95-102, doi:10.5194/ars-13-95-2015, 2015 In recent years Mobile Network Operators (MNOs) worldwide are extensively deploying LTE networks in different spectrum bands and utilising different bandwidth configurations. Initially, the deployment is coverage oriented with macro cells using the lower LTE spectrum bands. As the offered traffic (i.e. the requested traffic from the users) increases the LTE deployment evolves with macro cells expanded with additional capacity boosting LTE carriers in higher frequency bands complemented with micro or small cells in traffic hotspot areas. For MNOs it is crucial to use the LTE spectrum assets, as well as the installed network infrastructure, in the most cost efficient way. The dynamic spectrum allocation (DSA) aims at (de)activating the available LTE frequency carriers according to the temporal and spatial traffic variations in order to increase the overall LTE system performance in terms of total network capacity by reducing the interference. This paper evaluates the DSA potential of achieving the envisaged performance improvement and identifying in which system and traffic conditions the DSA should be deployed. A self-optimised network (SON) DSA algorithm is also proposed and evaluated. The evaluations have been carried out in a hexagonal and a realistic site-specific urban macro layout assuming a central traffic hotspot area surrounded with an area of lower traffic with a total size of approximately 8 × 8 km 2 . The results show that up to 47 % and up to 40 % possible DSA gains are achievable with regards to the carried system load (i.e. used resources) for homogenous traffic distribution with hexagonal layout and for realistic site-specific urban macro layout, respectively. The SON DSA algorithm evaluation in a realistic site-specific urban macro cell deployment scenario including realistic non-uniform spatial traffic distribution shows insignificant cell throughput (i.e. served traffic) performance gains. Nevertheless, in the SON DSA investigations, a gain of up to 25 % has been observed when analysing the resource utilisation in the non-hotspot cells.

Description: Charge pump design in 130 nm SiGe BiCMOS technology for low-noise fractional-N PLLs M. Kucharski and F. Herzel Adv. Radio Sci., 13, 133-139, doi:10.5194/ars-13-133-2015, 2015 This paper presents a charge pump (CP) designed for a high linearity and a low noise to be used in a fractional-N phase-locked loop (PLL). An internal supply regulator with low intrinsic device noise is included in the design optimization. The high CP linearity is shown to reduce the level of in-band spurs in a fractional-N PLL tremendously.

Description: Definition and test of the electromagnetic immunity of UAS for first responders C. Adami, S. Chmel, M. Jöster, T. Pusch, and M. Suhrke Adv. Radio Sci., 13, 141-147, doi:10.5194/ars-13-141-2015, 2015 Recent technological developments considerably lowered the barrier for unmanned aerial systems (UAS) to be employed in a variety of usage scenarios, comprising live video transmission from otherwise inaccessible vantage points. As an example, in the French-German ANCHORS project several UAS guided by swarm intelligence provide aerial views and environmental data of a disaster site while deploying an ad-hoc communication network for first responders. Since being able to operate in harsh environmental conditions is a key feature, the immunity of the UAS against radio frequency (RF) exposure has been studied. Conventional Electromagnetic Compatibility (EMC) applied to commercial and industrial electronics is not sufficient since UAS are airborne and can as such move beyond the bounds within which RF exposure is usually limited by regulatory measures. Therefore, the EMC requirements have been complemented by a set of specific RF test frequencies and parameters where strong sources are expected to interfere in the example project test case of an inland port environment. While no essential malfunctions could be observed up to field strengths of 30 V m −1 , a sophisticated, more exhaustive approach for testing against potential sources of interference in key scenarios of UAS usage should be derived from our present findings.

Description: A test method for analysing disturbed ethernet data streams M. Kreitlow, F. Sabath, and H. Garbe Adv. Radio Sci., 13, 149-153, doi:10.5194/ars-13-149-2015, 2015 Ethernet connections can suffer from data corruption due to intentional electromagnetic interference. In this paper a software-based measuring method is presented, which allows a direct assessment of the effects on the link layer without an unwanted influence of software related effects on higher protocol layers. This gives a simple tool for a quantitative analysis of the disturbance of an Ethernet connection based on time domain data.

Description: Analysis of the effect of different absorber materials and loading on the shielding effectiveness of a metallic enclosure S. Parr, H. Karcoon, S. Dickmann, and R. Rambousky Adv. Radio Sci., 13, 155-159, doi:10.5194/ars-13-155-2015, 2015 Absorbers used for improving the Shielding Effectiveness (SE) are compared in their electromagnetic performance. Therefore the permittivity and permeability are determined with a coaxial line experiment. The effect of loading in the form of metallic and dielectric structures inside a metallic enclosure on the SE is analyzed. It turns out, that the SE can be improved by using absorber. Also, the SE is affected by loading inside the metallic enclosure.

Description: A novel ZePoC encoder for sinusoidal signals with a predictable accuracy for an AC power standard T. Vennemann, T. Frye, Z. Liu, M. Kahmann, and W. Mathis Adv. Radio Sci., 13, 1-8, doi:10.5194/ars-13-1-2015, 2015 In this paper we present an analytical formulation of a Zero Position Coding (ZePoC) encoder for an AC power standard based on class-D topologies. For controlling a class-D power stage a binary signal with special spectral characteristics will be generated by this ZePoC encoder for sinusoidal signals. These spectral characteristics have a predictable accuracy within a separated baseband to keep the noise floor below a specified level. Simulation results will validate the accuracy of this novel ZePoC encoder. For a real-time implementation of the encoder on a DSP/FPGA hardware architecture a trade-off between accuracy and speed of the ZePoC algorithm has to be made. Therefore the numerical effects of different floating point formats will be analyzed.

Description: Reflexionseigenschaften von Windenergieanlagen im Funkfeld von Funknavigations- und Radarsystemen S. Sandmann, S. Divanbeigi, and H. Garbe Adv. Radio Sci., 13, 9-18, doi:10.5194/ars-13-9-2015, 2015 Die hier behandelte Untersuchung befasst sich mit den Störungen des elektrischen Feldes einer Doppler Very High Frequency Omnidirectional Radio Range Navigationsanlage (DVOR) in der Gegenwart von Windenergieanlagen (WEA). Hierfür wird die Feldstärke auf 25 konzentrischen Kreisbahnen, sog. Orbit Flights verschiedener Höhen und mit verschiedenen Radien rund um die DVOR-Anlage numerisch simuliert. Insbesondere werden die Einflüsse diverser Parameter der WEA wie deren Anzahl, Position, Rotorwinkel, Turmhöhe und Rotordurchmesser auf die Feldverteilung herausgestellt, sowie die Anwendbarkeit der Simulationsmethode Physical Optics (PO) durch Vergleich der Simulationsergebnisse mit denen der Multi Level Fast Multipol Method (MLFMM) untersucht.

Description: Efficient determination of the left-eigenvectors for the Method of Lines S. F. Helfert Adv. Radio Sci., 13, 19-29, doi:10.5194/ars-13-19-2015, 2015 To enforce the continuity of transverse electric and magnetic fields at boundaries, rectangular matrices containing the field distribution ('right eigenvectors') have to be inverted. This can be done with left eigenvectors. Here, it is shown how the latter ones can be determined with simple matrix products from previously determined right eigenvectors. For this purpose the relation between the transverse electric and magnetic fields known from Maxwell's equations is utilized.

Description: A programmable energy efficient readout chip for a multiparameter highly integrated implantable biosensor system M. Nawito, H. Richter, A. Stett, and J. N. Burghartz Adv. Radio Sci., 13, 103-108, doi:10.5194/ars-13-103-2015, 2015 In this work an Application Specific Integrated Circuit (ASIC) for an implantable electrochemical biosensor system is presented. The ASIC drives the measurement electrodes and performs amperometric measurements for determining the oxygen concentration, potentiometric measurements for evaluating the pH‐level as well as temperature measurements. The chip was fabricated and shows good result which conform to the Simulation data.

Description: High-voltage circuits for power management on 65 nm CMOS S. Pashmineh and D. Killat Adv. Radio Sci., 13, 109-120, doi:10.5194/ars-13-109-2015, 2015 This paper presents two high-voltage circuits used in power management, a switching driver for buck converter with optimized on-resistance and a low dropout (LDO) voltage regulator with 2-stacked pMOS pass devices. The circuit design is based on stacked MOSFETs, thus the circuits are technology independent.

Description: Design investigation to improve voltage swing and bandwidth of the SiGe driver circuit for a silicon electro-optic ring modulator A. Fatemi, H. Gaul, U. Keil, and H. Klar Adv. Radio Sci., 13, 121-125, doi:10.5194/ars-13-121-2015, 2015 This paper reports on a new SiGe driver IC to address the low breakdown voltage level of modern BiCMOS transistors. An optical modulator driver IC in SiGe 250 nm technology with a supply voltage of 4.5 V is presented. This driver IC consists of pre- and main driver stages where a newly modified cascode topology and capacitance degeneration technique is employed to meet current application requirements; high voltage swing at high datarate.

Description: Impedance spectra classification for determining the state of charge on a lithium iron phosphate cell using a support vector machine P. Jansen, D. Vergossen, D. Renner, W. John, and J. Götze Adv. Radio Sci., 13, 127-132, doi:10.5194/ars-13-127-2015, 2015 New method for determining the state of charge on lithium iron phosphate cells using frequency domain data.

Description: Comparison of electromagnetic solvers for antennas mounted on vehicles M. S. L. Mocker, S. Hipp, F. Spinnler, H. Tazi, and T. F. Eibert Adv. Radio Sci., 13, 49-55, doi:10.5194/ars-13-49-2015, 2015 An electromagnetic solver comparison for various use cases of antennas mounted on vehicles is presented. For this purpose, several modeling approaches, called transient, frequency and integral solver, including the features fast resonant method and autoregressive filter, offered by CST MWS, are investigated. The solvers and methods are compared for a roof antenna itself, a simplified vehicle, a roof including a panorama window and a combination of antenna and vehicle. With these examples, the influence of different materials, data formats and parameters such as size and complexity are investigated. Also, the necessary configurations for the mesh and the solvers are described.

Description: Validation of the radiation pattern of the VHF MST radar MAARSY by scattering off a sounding rocket's payload T. Renkwitz, C. Schult, R. Latteck, and G. Stober Adv. Radio Sci., 13, 41-48, doi:10.5194/ars-13-41-2015, 2015 The Middle Atmosphere Alomar Radar System (MAARSY) is a monostatic radar with an active phased array antenna designed for studies of phenomena in the mesosphere and lower thermosphere. Its design, in particular the flexible beam forming and steering capability, makes it a powerful instrument to perform observations with high angular and temporal resolution. For the configuration and analysis of experiments carried out with the radar it is essential to have knowledge of the actual radiation pattern. Therefore, during the time since the radar was put into operation various active and passive experiments have been performed to gain knowledge of the radiation pattern. With these experiments the beam pointing accuracy, the beam width and phase distribution of the antenna array were investigated. Here, the use of a sounding rocket and its payload as a radar target is described which was launched in the proximity of the radar. The analysis of these observations allows the detailed investigation of the two-way radiation pattern for different antenna array sizes and beam pointing positions.

Description: An active UHF RFID localization system for fawn saving M. Eberhardt, M. Lehner, A. Ascher, M. Allwang, and E. M. Biebl Adv. Radio Sci., 13, 87-94, doi:10.5194/ars-13-87-2015, 2015 This paper presents a localization concept for fawn saving. Fawns can be saved during pasture mowing by marking them with an active UHF RFID transponder. The system consists of a mowing-machine mounted direction-of-arrival (DOA) system and a handheld DOA device. Only by estimating the DOA one can reliable localize the marked fawns. The whole RFID and DOA system is presented and communication concept is shown.

Description: A high throughput architecture for a low complexity soft-output demapping algorithm I. Ali, U. Wasenmüller, and N. Wehn Adv. Radio Sci., 13, 73-80, doi:10.5194/ars-13-73-2015, 2015 Iterative channel decoders such as Turbo-Code and LDPC decoders show exceptional performance and therefore they are a part of many wireless communication receivers nowadays. These decoders require a soft input, i.e., the logarithmic likelihood ratio (LLR) of the received bits with a typical quantization of 4 to 6 bits. For computing the LLR values from a received complex symbol, a soft demapper is employed in the receiver. The implementation cost of traditional soft-output demapping methods is relatively large in high order modulation systems, and therefore low complexity demapping algorithms are indispensable in low power receivers. In the presence of multiple wireless communication standards where each standard defines multiple modulation schemes, there is a need to have an efficient demapper architecture covering all the flexibility requirements of these standards. Another challenge associated with hardware implementation of the demapper is to achieve a very high throughput in double iterative systems, for instance, MIMO and Code-Aided Synchronization. In this paper, we present a comprehensive communication and hardware performance evaluation of low complexity soft-output demapping algorithms to select the best algorithm for implementation. The main goal of this work is to design a high throughput, flexible, and area efficient architecture. We describe architectures to execute the investigated algorithms. We implement these architectures on a FPGA device to evaluate their hardware performance. The work has resulted in a hardware architecture based on the figured out best low complexity algorithm delivering a high throughput of 166 Msymbols/second for Gray mapped 16-QAM modulation on Virtex-5. This efficient architecture occupies only 127 slice registers, 248 slice LUTs and 2 DSP48Es.

Description: Correlation of BAW and SAW properties of langasite at elevated temperatures Journal of Sensors and Sensor Systems, 4, 331-340, 2015 Author(s): M. Schulz, E. Mayer, I. Shrena, D. Eisele, M. Schmitt, L. M. Reindl, and H. Fritze The full set of electromechanical data of langasite (La 3 Ga 5 SiO 14 ) is determined in the temperature range from 20 to 900 °C using differently oriented bulk acoustic wave resonators. For data evaluation a physical model of vibration is developed and applied. Thereby, special emphasis is taken on mechanical and electrical losses at high temperatures. The resulting data set is used to calculate the properties of surface acoustic waves. Direct comparison with experimental data such as velocity, coupling coefficients and propagation loss measured using surface acoustic wave devices with two different crystal orientations shows good agreement.

Description: Flexible free-standing SU-8 microfluidic impedance spectroscopy sensor for 3-D molded interconnect devices application Marc-Peter Schmidt, Aleksandr Oseev, Christian Engel, Andreas Brose, Bertram Schmidt, and Sören Hirsch J. Sens. Sens. Syst., 5, 55-61, doi:10.5194/jsss-5-55-2016, 2016 The article reports about the development of novel microfluidic sensors that are directly attachable on 3-D polymers. An ability to integrate electrical and fluidic parts into the 3-D platform brings the sensors to a new level of miniaturization. The sensor system is made of a flexible polymer featuring a system of metal electrodes and a rigid polymer carrier with all external macroconnections. To the concentration of ethanol in DI water the sensor system showed the desired sensitivity.

Description: Combination of clustering algorithms to maximize the lifespan of distributed wireless sensors Derssie D. Mebratu and Charles Kim J. Sens. Sens. Syst., 5, 63-72, doi:10.5194/jsss-5-63-2016, 2016 Many different techniques have been introduced in an effort to maximize heterogeneous wireless sensor lifespan, but these techniques have focused on having the nodes in a cluster send their data to a selected cluster head node that, in turn, reports the data to the base station. Therefore, the choice of the number of clusters and the way the cluster head node is selected are the main focuses of this research paper.

Description: Local Dynamic Map als modulares Software Framework für Fahrerassistenzsysteme Advances in Radio Science, 13, 203-207, 2015 Author(s): P. Reisdorf, A. Auerswald, and G. Wanielik Moderne Fahrerassistenzsysteme basieren auf der Verarbeitung von Informationen, welche durch die Umfeldwahrnehmung mit unterschiedlicher Sensorik erfolgt. Neben den Informationen aus dem eigenen Fahrzeug ergeben sich durch unterschiedliche Kommunikationsmöglichkeiten (Car2Car, Car2X,...) erweiterte Umfeldwahrnehmungen (siehe Abb. 1). Diese Daten gilt es aufbereitet und zielorientiert einer Anwendung zur Verfügung zu stellen, was mit Hilfe einer Local Dynamic Map (LDM) erfüllt werden kann. Die vorliegende Veröffentlichung beschreibt den Aufbau, Verwendungszweck und Eigenschaften einer entwickelten LDM und geht auf einige Applikationen ein, die mit Hilfe dieser realisiert wurden.

Description: Understanding and optimizing microstrip patch antenna cross polarization radiation on element level for demanding phased array antennas in weather radar applications Advances in Radio Science, 13, 251-268, 2015 Author(s): D. Vollbracht The antenna cross polarization suppression (CPS) is of significant importance for the accurate calculation of polarimetric weather radar moments. State-of-the-art reflector antennas fulfill these requirements, but phased array antennas are changing their CPS during the main beam shift, off-broadside direction. Since the cross polarization (x-pol) of the array pattern is affected by the x-pol element factor, the single antenna element should be designed for maximum CPS, not only at broadside, but also for the complete angular electronic scan (e-scan) range of the phased array antenna main beam positions. Different methods for reducing the x-pol radiation from microstrip patch antenna elements, available from literature sources, are discussed and summarized. The potential x-pol sources from probe fed microstrip patch antennas are investigated. Due to the lack of literature references, circular and square shaped X-Band radiators are compared in their x-pol performance and the microstrip patch antenna size variation was analyzed for improved x-pol pattern. Furthermore, the most promising technique for the reduction of x-pol radiation, namely "differential feeding with two RF signals 180° out of phase", is compared to single fed patch antennas and thoroughly investigated for phased array applications with simulation results from CST MICROWAVE STUDIO (CST MWS). A new explanation for the excellent port isolation of dual linear polarized and differential fed patch antennas is given graphically. The antenna radiation pattern from single fed and differential fed microstrip patch antennas are analyzed and the shapes of the x-pol patterns are discussed with the well-known cavity model. Moreover, two new visual based electromagnetic approaches for the explanation of the x-pol generation will be given: the field line approach and the surface current distribution approach provide new insight in understanding the generation of x-pol component in microstrip patch antenna radiation patterns.

Description: Networks of high frequency inhomogeneous transmission lines Advances in Radio Science, 13, 189-195, 2015 Author(s): F. Ossevorth, H. G. Krauthäuser, S. Tkachenko, J. Nitsch, and R. Rambousky It is well known from classical transmission line theory, that transmission lines can be folded into impedances and thereby used in an electrical network setting. But it is also possible to create large networks of transmission lines consisting of tubes and junctions. The tubes contain the transmission lines and the junctions consider the mutual influences of the adjacent tubes or the terminals. The calculation of the currents and voltages at the junctions can be performed with the help the BLT-equation. So far this method is not applicable for nonuniform transmission lines described in a full wave method, because the lack of a distinct voltage gives no possibility for junctions. Junctions only make sense, when the considered network offers the possibility to propagate a TEM-Mode. If this requirement is fullfilled, nonuniform transmission lines could be included in an electrical network. This approach is validated in this paper in form of numerical simulations as well as measurements.

Description: Influence of operation temperature variations on NO measurements in low concentrations when applying the pulsed polarization technique to thimble-type lambda probes Journal of Sensors and Sensor Systems, 4, 321-329, 2015 Author(s): S. Fischer, D. Schönauer-Kamin, R. Pohle, M. Fleischer, and R. Moos By applying the pulsed polarization technique, a thimble-type lambda probe can be used as a NO x sensor in the low ppm range. Due to the robustness of the sensor in harsh exhaust gas environments, this approach has many opportunities for application. The temperature operating range for best NO sensing properties is a crucial parameter. The sensor temperature changes with the ambient gas temperature, but can be stabilized actively by internal heating in a certain temperature range. This study evaluates in detail the temperature influence on NO sensitivity, so that an optimum operating point can be derived from these results using a dynamic measurement technique. Stepwise NO concentration changes between 0 and 12.5 ppm in synthetic exhausts demonstrate the potential of the concept.