L. Reindl

University of Freiburg, Freiburg, Baden-Württemberg, Germany

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Publications (259)99.5 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Mice and rats make up 95 percent of all animals used in medical research and drug discovery and development. Monitoring of physiological functions such as ECG, blood pressure, and body temperature over the entire period of an experiment is often required. Restraining of the animals in order to obtain this data can cause great inconvenience. The use of telemetric systems solves this problem and provides more reliable results. However, these devices are mostly equipped with batteries, which limit the time of operation or they use passive power supplies, which affects the operating range. The semi-passive telemetric implant being presented is based on RFID technology and overcomes these obstacles. The device is inductively powered using the magnetic field of a common RFID reader device underneath the cage, but is also able to operate for several hours autonomously. Being independent from the battery capacity, it is possible to use the implant over a long period of time or to re-use the device several times in different animals, thus avoiding the disadvantages of existing systems and reducing the costs of purchase and refurbishment.
    Sensors and Actuators A Physical 11/2014; · 1.94 Impact Factor
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    ABSTRACT: Telemetry systems enable researchers to continuously monitor physiological signals in unrestrained, freely moving small rodents. Drawbacks of common systems are limited operation time, the need to house the animals separately, and the necessity of a stable communication link. Furthermore, the costs of the typically proprietary telemetry systems reduce the acceptance. The aim of this paper is to introduce a low-cost telemetry system based on common radio frequency identification (RFID) technology optimized for battery independent operational time, good reusability, and flexibility. The presented implant is equipped with sensors to measure electrocardiogram (ECG), arterial blood pressure, and body temperature. The biological signals are transmitted as digital data streams. The device is able to monitor several freely moving animals housed in groups with a single reader station. The modular concept of the system significantly reduces the costs to monitor multiple physiological functions and refining procedures in preclinical research.
    IEEE transactions on bio-medical engineering 10/2014; · 2.15 Impact Factor
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    ABSTRACT: Today, the vast majority of personal communication devices, such as laptops, smartphones, and logically wireless fidelity (Wi-Fi) access points feature IEEE 802.11 chipsets. In turn, wake-up radio (WuR) systems are used to reduce the significant energy waste that wireless devices cause during their idle communication mode. A novel WuR system is introduced that enables any IEEE 802.11-enabled device to be used as a WuR transmitter without requiring any hardware modification. The corresponding developed WuR receiver achieves a remarkably low power consumption of 10.8 -W and operates in the Wi-Fi 2.4 GHz band. By means of thorough physical tests, it is shown that the proposed IEEE 802.11-based WuR system enables important energy savings.
    Electronics Letters 09/2014; 50(20):1484-1486. · 1.07 Impact Factor
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    Antwi Nimo, Joan Albesa, Leonhard M. Reindl
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    ABSTRACT: This work presents the effect of parasitic components on the performance of wireless RF energy harvesters. Since ambient RF power density is low, only optimal wireless RF energy harvesters will be able to power remote microwatt sensors. By knowing the effect of each parasitic component on the performance of wireless RF harvesters, components may be realized or selected that increases the overall efficacy of the harvester. The analytical and experimental investigation of the component parastics on the harvester output performance is compared at various operating frequencies; both at HF and UHF.
    Multi-Conference on Systems, Signals & Devices (SSD), 2014 11th International, Barcelona; 02/2014
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    ABSTRACT: This paper presents a novel torque sensing concept, based on resonant perturbation of an open parallel plate dielectric resonator. When torque is applied to the shaft, the air gap between the parallel plates fixed on a clamp system is changed, which in turn shifts the frequency of the dielectric resonator. Finite Element Method (FEM) simulations using HFSS (ANSYS®) and experimental results regarding the effects of air gap variation on the TE01δ mode in the 2-3 GHz range are presented to prove the sensing concept.
    2014 11th International Multi-Conference on Systems, Signals & Devices (SSD); 02/2014
  • Gerd Ulrich Gamm, Sebastian Stoecklin, Leonhard Michael Reindl
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    ABSTRACT: Sensor nodes often have to work for a long time with a single battery. A change of the power source is sometimes not possible or involves effort and costs. If the node needs to be accessible for communication at any point of time it must have a radio in permanent receive state. This depletes the battery in a few days. The contradiction between long lifetime and permanent accessibility can be solved by using a separate wake-up receiver on the node. In this work we present a sensor node with included wake-up receiver working in the 433MHz ISM band. Our solution consumes 2.8 μA of current in sleep state while still maintaining a realtime behaviour. The low current consumption is achieved by modulating a 125 kHz wake-up signal on the 433MHz carrier in the sender. In the receiving node a passive demodulation circuit extracts the wake-up signal and feeds it to an 125 kHz low frequency receiver IC. An additional 16 bit address coding is used for an selective wake-up of nodes.
    2014 11th International Multi-Conference on Systems, Signals & Devices (SSD); 02/2014
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    ABSTRACT: This paper presents the results of a German research project aiming at improving Urban Search And Rescue (USAR). It comprises two wireless search technologies for the detection and localization of trapped or buried unconscious victims and auxiliary assisting technologies. Victims can be localized through their cellular phone (GSM) if it is active, but it might be out of order. Results detecting inactive phones are presented. However, with this technology a victim without cellular phone cannot be detected. In this case, a ground-penetrating, continuous wave radar can be used that is as well presented. A channel model for estimating signal disturbances in debris between victim and receiving antenna is proposed that aims at improving the accuracy of these technologies. Furthermore, the I-LOV system assists decision-makers by a mobile IT-system called FRIEDAA that allows gathering, processing, and representation of relevant information such as search results and personnel locations in real time. Therefore, infrastructure and inertial sensor based personal localization systems are presented.
    Ad Hoc Networks 02/2014; 13:69–82. · 1.94 Impact Factor
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    ABSTRACT: The power conversion efficiency of photovoltaic devices depends strongly on the light spectrum and light intensity. Both parameters vary significantly between different environments and locations - indoors as well as outdoors. Since placement of energy harvesting devices is governed more by the intended functionality of the system than by optimizing with respect to light conditions, the knowledge of light conditions in different environments is necessary for the design and dimensioning of photovoltaic energy converters. With this paper we want to present a simple approach to systematically measure and analyze light conditions and energy availability in different environments and to provide the basis for the development of a database of 'typical' light conditions. This will help to understand the energy availability and the dimensioning and design of photovoltaic devices in energy harvesting systems.
    2014 11th International Multi-Conference on Systems, Signals & Devices (SSD); 02/2014
  • Algorithms for Sensor Systems, Edited by Flocchini, Paola and Gao, Jie and Kranakis, Evangelos and Meyer auf der Heide, Friedhelm, 01/2014: pages 35-50; Springer Berlin Heidelberg., ISBN: 9783642453458
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    ABSTRACT: With the development of new integrated circuits to interface radio frequency identification protocols, inductive air interfaces have become more and more important. Near field communication is not only able to communicate, but also possible to transfer power wirelessly and to build up passive devices for logistical and medical applications. In this way, the power management on the transponder becomes more and more relevant. A designer has to optimize power consumption as well as energy harvesting from the magnetic field. This paper discusses a model with simple equations to improve transponder antenna matching. Furthermore, a new numerical analysis technique is presented to calculate the coupling factors, inductions, and magnetic fields of multiantenna systems.
    IEEE Transactions on Magnetics 01/2014; 50(6):1-9. · 1.21 Impact Factor
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    Quirin Hamp, Leonhard Reindl, Denise Güthlin
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    ABSTRACT: The objective of assisting with tasks and decisions during incident response is to reduce the risks to victims and rescue personnel while increasing the efficiency of the rescue operation. Handling uncertain information during urban search and rescue (USAR) missions represents additional stress to the decision-maker. The aim of this study is to identify the decision-making behaviour of rescuers during USAR missions to pinpoint trapped or buried victims in debris in order to design assistance technologies and decision-support systems that meet their needs. In 2010, a survey was conducted among 10-15 per cent of all German rescue personnel specialised in search tasks. One of the major results of this survey is that a subjective assessment of the reliability of information available from heterogeneous sources influences the rescuers' actions and that there is no methodology for decision-making involving uncertain information. In addition, the study found that compliance with procedures does not require assistance.
    Disasters 01/2014; 38(1):84-107. · 0.69 Impact Factor
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    ABSTRACT: The use of the package as a radiating element is the optimal solution in term of robustness for wireless sensor network (WSN) applications such as infrastructure monitoring. A robust, 83 % efficient and 6.5 dBi gain slot antenna packaging (simulation values in air) for wireless sensor nodes working at 868 MHz is presented in this paper. A low power wake-up radio transceiver strategy allowing a current consumption of 3.8 μA is associated to the radiating package. The theoretical battery life time for a 3 V input voltage and a 220 mA/h battery capacity is more than 6 years using the proposed system. Therefore the combination between the antenna packaging and wake-up approach increases the wireless system life time. Finite Element Method (FEM) simulation and experimental results are presented to show the effects of different concrete supports on the antenna performances. Moreover, indoor and outdoor wake-up rate measurements show the coverage efficiency of the complete device. Using a transmission power of +10 dBm and a wake-up sensitivity of -51.8 dBm, a distance of 55 meters is reached in comparison to more than 250 meters for data transmission.
    2013 IEEE Conference on Wireless Sensor (ICWISE); 12/2013
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    ABSTRACT: The use of duty-cycling in Medium Access Control (MAC) protocols effectively helps improving the energy efficiency of wireless networks. However, while the benefits of these protocols are unquestionable, most of them still suffer from overhearing and idle listening, two issues that prevent duty-cycled systems from achieving optimum energy usage, which is a crucial aspect in specific types of wireless networks such as Wireless Sensor Networks (WSN).Wake-up Radio (WuR) systems have been employed recently to overcome these issues. Under this approach, the nodes' MicroController Unit (MCU) and main radio transceiver are completely switched off and only activated when a secondary, extremely low-power receiver in the node is triggered by a particular wireless transmission. Wake-up Radio systems allow for drastic energy savings since receiver nodes are only activated on-demand, maximizing their battery lifetimes. In this paper, we have modeled and simulated a real, recent and promising WuR hardware platform based on its time and energy consumption characterization. By comparing such WuR approach to B-MAC and IEEE 802.15.4, two well-known and widely employed MAC protocols, we show it effectively out-performs the conventional WSN MAC approaches in terms of energy efficiency. To the best of authors' knowledge, this is the first study to include a comparative analysis for multi-hop networks based on a real WuR platform, which shows WuR systems represent an energy-efficient solution that also provides a good tradeoff between latency, packet delivery ratio and applicability..
    Proceedings of the 16th ACM international conference on Modeling, analysis & simulation of wireless and mobile systems; 11/2013
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    ABSTRACT: Localization based on the time difference of arrival (TDoA) has turned out to be a promising approach for indoor environments, especially in combination with innovative self-calibrating TDoA algorithms that eliminate the need to measure the positions of reference receivers. We consider the previously unsolved problem of locating a moving target receiver by discrete signals from stationary beacons at unknown locations. We assume that the beacons are small and inexpensive and they require no further communication, i.e. they are unsynchronized. They only emit short discrete signals at regular intervals, of which we assume that they can be distinguished. The moving target travels on an unknown trajectory, receiving signals from the beacons and calculating the TDoA of the signals. First, we discuss adaptions of two TDoA algorithms by which the senders can be located from unknown signals. Second, we propose two novel approaches based on probabilistic state estimation to enable robust localization of the mobile receiver using the discrete arrival times, once the senders have been located. The probabilistic algorithms use the particle filter and the unscented Kalman filter to estimate the position and velocity of the target, as well as the unknown synchronization offsets of the senders. We provide a motion model and a sensor model for which we take into account that the signals of the beacons are received as singles, each at a different time. We verify the feasibility and robustness of our approach in extensive simulations, where we analyze the reliability of localization and compare both algorithms.
    2013 International Conference on Indoor Positioning and Indoor Navigation (IPIN); 10/2013
  • M. Freunek, L.M. Reindl
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    ABSTRACT: In the above paper (ibid., vol 3, no. 1, pp. 59-64, Jan. 2013), there is an error in the scale of Fig. 1. The corrected figure should appear as presented here. The correct maximum efficiency following the detailed balance model is close to 30% for a halogen lamp and for an incandescent bulb, respectively, and a bandgap close to the one of Germanium. The fluorescent tube reaches 50%, and the white RGB LED and the Phosphor LED achieve 64% and 57%, respectively. The maximum photovoltaic efficiency is 72% when irradiated by a sodium discharge lamp.
    IEEE Journal of Photovoltaics 10/2013; 3(4):1464-1464. · 3.00 Impact Factor
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    Antwi Nimo, Dario Grgić, Tolgay Ungan, Leonhard M Reindl
    Microwave Conference (EuMC), 2013 43nd European; 10/2013
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    ABSTRACT: This paper presents a strain transfer investigation for Surface Acoustic Wave (SAW) strain sensors. For evaluation, a SAW strain sensor is assembled with a pre-tested bond material for potentially high strain transfer on a test holder. The setup is stressed with an axially homogeneous strain up to 500 ppm. The strain transfer ratio is computed from the applied load, the reference measurements with foil strain gauge, and the measured SAW strain sensor signal. The strain transfer performance of the bond material is also investigated with respect to the temperature dependency in the range between 22 °C and 85 °C. At this elevated temperatures an average strain transfer ratio of 0.606 ± 0.7% was measured. Mechanical load cycling tests up to 1000 cycles are used for the evaluation of the elastic fatigue of the bond material. The effects of mechanical load cycling and aging of the bond layer are analyzed with the SAW strain sensor response. After 1000 mechanical load cycles the transferred strain into the SAW strain sensor is 0.582 ± 0.153%. Finally, the experimental results are compared with the results of a 3D FEM simulation which are deviating less than 10%.
    ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems; 07/2013
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    ABSTRACT: This paper presents a strain and stress sensitivity investigation of surface acoustic wave (SAW) strain sensors on chip-level. Longitudinal and transversal orientated SAW strain sensors are homogeneously loaded. The sensors response is measured and analyzed with a network analyzer while the sensor substrate stripes are strained precisely. An optical 3D deformation analysis system is used for reference strain measurements. The determined strain on chip-level is compared with strain calculations. High precision strain and stress sensitivities are presented without the cross effects of multilayer measurement setups.
    2013 IEEE International Ultrasonics Symposium (IUS); 07/2013
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    ABSTRACT: The main idea behind this project is to provide a unified platform which will cover a complete process for embedded systems learning. A modular approach is considered for skills practice through supporting individualization in learning. This platform shall facilitate a novel development of universal approach in creative learning environment and knowledge management that encourage use of ICT. New learning model is challenging the education of engineers in embedded systems design through real-time experiments that stimulate curiosity with ultimate goal to support students to understand and construct their personal conceptual knowledge based on experiments. In addition to the technological approach, the use of cognitive theories on how people learn will help students to achieve a stronger and smarter adaptation of the subject. Applied methodology will be evaluated from the scientific point of view in parallel with the implementation in order to feedback results to the R&D.
    16th Euromicro Conference on Digital System Design DSD 2013, Santander, Spain; 06/2013
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    ABSTRACT: We present an approach for the localisation of passive receiver nodes in a communication network. The only source of information is the time when environmental sound or ultrasound signals are received. The discrete signals occur at unknown positions and times, but they can be distinguished. The clocks of the receivers are synchronised, so the time differences of arrival TDOA of the signals can be computed. The goal is to determine the relative positions of all receiver nodes and implicitly the positions and times of the environmental signals. Our proposed approach, the Cone Alignment algorithm, solves iteratively a nonlinear optimisation problem of TDOA using a physical spring–mass simulation. We present a geometrical representation of the error function, which is modelled by physical springs. By iterative relaxation of the springs, the error function is minimised. The approach is tested in numerous simulations, whereby our algorithm shows a smaller tendency to get stuck in local minima than a nonlinear least-squares approach using gradient descent. In experiments in a real-world setting, we demonstrate and evaluate a tracking system for a moving ultrasound beacon without the need to initially calibrate the positions of the receivers. Using our algorithm, we estimate the trajectory of a moving model train and of an RC car with a precision in the range of few centimetres.
    Journal of Location Based Services 06/2013; 7(2):121-144.

Publication Stats

2k Citations
99.50 Total Impact Points


  • 2004–2014
    • University of Freiburg
      • Department of Microsystems Engineering (IMTEK)
      Freiburg, Baden-Württemberg, Germany
  • 2012
    • Evangelische Hochschule Freiburg, Germany
      Freiburg, Baden-Württemberg, Germany
  • 2010
    • Bosch GmbH
      Gerlingen, Baden-Württemberg, Germany
  • 2006
    • Max Planck Institute for Solar System Research
      Göttingen, Lower Saxony, Germany
    • Tohoku University
      • Department of Nanomechanics
      Sendai-shi, Miyagi-ken, Japan
  • 2004–2006
    • Carinthian Tech Research AG
      Villach, Carinthia, Austria
  • 1988–2006
    • Siemens
      München, Bavaria, Germany
  • 2003–2005
    • Paul Drude Institute for Solid State Electronics
      Berlín, Berlin, Germany
  • 1999–2003
    • Technische Universität Clausthal
      Bergstadt-Clausthal-Zellerfeld, Lower Saxony, Germany
    • University of Vienna
      Wien, Vienna, Austria
  • 1998–2000
    • Johannes Kepler University Linz
      • Institut für Nachrichtentechnik und Hochfrequenzsysteme
      Linz, Upper Austria, Austria
  • 1995–2000
    • Vienna University of Technology
      Wien, Vienna, Austria
  • 1996
    • University of Oulu
      • Electronics Laboratory
      Oulu, Oulu, Finland