Leo Reindl | Albert-Ludwigs-Universität Freiburg (original) (raw)

Papers by Leo Reindl

IEEE Sensors Journal, 2016

IEEE Conference Proceedings, 2016

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Nov 1, 2004

Surface acoustic wave (SAW) devices can be used as wireless sensor elements, called SAW transpond... more Surface acoustic wave (SAW) devices can be used as wireless sensor elements, called SAW transponders, for measuring physical quantities such as temperature that do not need any power supply and may be accessed wirelessly. A complete wireless sensor system consists of one or more such SAW transponders and a local radar transceiver. The SAW transponder receives an RF burst in the VHF/UHF band transmitted by the radar transceiver. The reader unit performs a radar measurement of the impulse response of the SAW transponder via a high-frequency electromagnetic radio link. A temperature variation changes the SAW velocity and thereby the response pattern of the SAW device. By analyzing the time delay between backscattered pulses with different time delays we get a rough estimation of the temperature of the SAW transponder. By using this information the ambiguity of +/-2pi in the phase differences between the pulses can be eliminated, which provides an overall and unambiguous temperature resolution of +/-0.2 degrees C.

IEEE ACM Transactions on Networking, 2016

For the first time we present an on-disk wireless temperature measurement system (Fig.1) for cen... more For the first time we present an on-disk wireless temperature measurement system (Fig.1) for centrifugal microfluidic platforms[1]. Tiny thermistors with a volume of 54nl allow the direct temperature measurement in almost any of cavity (Fig.2) of microfluidic chips with a resolution of 0.1 K. A rotating radio module transfers digitalized data to a stationary receiver with D/A converter being connected to a temperature controller. The total response time of the temperature measurement system is 9.6 ms. The rotating electronic elements are powered by inductive coupling with up to 2W. The radio transmission of sensor data can be parameterized by any commercial PC via USB port. This system enables to precisely measure the temperature of fluids in centrifugal microfluidic systems and hence allows closed-loop control of direct heating systems e.g. IR radiators for fast Polymerase Chain Reaction (PCR) thermocycling processes.

Journal of Advanced Dielectrics

The theory and application of resonances and vibrational modes are part of the foundation of scie... more The theory and application of resonances and vibrational modes are part of the foundation of science. In this contribution, examples of acoustical resonators are highlighted, and compared to electromagnetic modes. As an example from architecture, we describe the phenomenon of whispering galleries; such modes are nowadays known in dielectric and optical resonators. A specimen of a semicircular whispering bench in Park Sanssouci in Potsdam is acoustically investigated and demonstrated to show low losses for sound propagation. A special acoustical bug is discussed which was used for the espionage of the U.S. ambassador in Moscow. The Sovyets could interrogate this passive device by radio waves. Its working principle was based on the electromagnetic resonance of the cavity that the sound-sensitive membrane was part of. The underlying relation between excitation and resonance is compared to the sound production in flue organ pipes. A stopped flue organ pipe was investigated using a piezo...

† These authors contributed equally to this work. Abstract: Accurate measurements of global solar... more † These authors contributed equally to this work. Abstract: Accurate measurements of global solar radiation, atmospheric temperature and relative humidity, as well as the availability of the predictions of their evolution over time, are important for different areas of applications, such as agriculture, renewable energy and energy management, or thermal comfort in buildings. For this reason, an intelligent, light-weight, self-powered and portable sensor was developed, using a nearest-neighbors (NEN) algorithm and artificial neural network (ANN) models as the time-series predictor mechanisms. The hardware and software design of the implemented prototype are described, as well as the forecasting performance related to the three atmospheric variables, using both approaches, over a prediction horizon of 48-steps-ahead.

Elektrische Messtechnik, 2014

2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)

Various measurement systems can be used to obtain dynamic circumferences of the human upper body,... more Various measurement systems can be used to obtain dynamic circumferences of the human upper body, but each of these systems has disadvantages. In this feasibility study we introduce a non-invasive and wearable thoracic belt to measure dynamic changes of circumferences of thorax or abdomen. To evaluate this approach, five subjects undertook various breaths of disparate tidal volumes, which were measured by the belt and simultaneously by a motion capture system which provided a reference metric.The results of the belt concurred with the reference system. A coefficient of determination (adjusted R2) of 0.99 and a mean squared error of less than 0.87 mm2 showed that the belt is capable of measuring changes accurately and a couple of respiratory parameters, such as the respiratory rate, can be obtained.Clinical Relevance—The introduced system links surface motions of the upper body with the underlying respiratory mechanics. Thus it provides some respiratory parameters without the disadvantages of a facemask or a mouthpiece. The system could allow the analysis of breathing status in some clinical applications and could be used for low-cost monitoring in homecare or to analyse respiratory parameters during sports.

IEEE Transactions on Microwave Theory and Techniques

Millimeter wave-based material inspection methods are capable of providing 3-D-tomographic images... more Millimeter wave-based material inspection methods are capable of providing 3-D-tomographic images of composite materials with a sufficient resolution to detect, localize, and classify critical defects. The nondestructive and noncontact-based measurement methods’ potential can only be utilized with a complete understanding of the signals propagation behavior. Such that the relevant signal processing is tailored to the respective application. A core challenge of these systems remains clutter mitigation. Due to the composite materials’ structure, a significant component of the received signal is corrupted by internal reflections, manifesting as clutter. For this purpose, a variety of different clutter mitigation methods, which include: normalization, moving average and moving median filter, entropy-based filtering, time gating, spatial filtering, and singular value decomposition, are investigated. These methods are applied to tomographic data of glass fiber reinforced plastic components, acquired via a W{W}W -band imaging system.

Abstract: Recent advances in nanotechnology, electronic technology and biology have enabled the d... more Abstract: Recent advances in nanotechnology, electronic technology and biology have enabled the development of bio-inspired nanoscale sensors. The cooperation among the bionanosensors in a network is envisioned to perform complex tasks. Clock synchronization is essential to establish diffusion-based distributed cooperation in the bionanosensor networks. This paper proposes a maximum-likelihood estimator of the clock offset for the clock synchronization among molecular bionanosensors. The unique properties of diffusion-based molecular communication are described. Based on the inverse Gaussian distribution of the molecular propagation delay, a two-way message exchange mechanism for clock synchronization is proposed. The maximum-likelihood estimator of the clock offset is derived. The convergence and the bias of the estimator are analyzed. The simulation results show that the proposed estimator is effective for the offset compensation required for clock synchronization. This work paves...

International Journal of Disaster Risk Reduction, 2016

Information gathering in tunnels, buildings, bridges, etc. during disasters is of vital importanc... more Information gathering in tunnels, buildings, bridges, etc. during disasters is of vital importance in speeding up rescue efforts and for protecting the fire fighters. The collected data can be used by the emergency services in the planning of rescue operations and allocation of human resources at a local level. In this article we present design and implementation of a wireless sensor network, which consists of energy-efficient wireless sensor nodes with an integrated ultrasonic sensor, which establish a collision free data transmission in an emergency scenario. The developed network was tested in a field experiment in an explosion within a building to confirm its functionality and reliability. The wireless sensor network was able to pass critical data to the emergency units to initiate the rescue procedures during this disaster scenario.

Sensors, 2015

The multipath spread in underwater acoustic channels is severe and, therefore, when the symbol ra... more The multipath spread in underwater acoustic channels is severe and, therefore, when the symbol rate of the time reversal (TR) acoustic communication using single-carrier (SC) modulation is high, the large intersymbol interference (ISI) span caused by multipath reduces the performance of the TR process and needs to be removed using the long adaptive equalizer as the post-processor. In this paper, a TR acoustic communication method using filtered multitone (FMT) modulation is proposed in order to reduce the residual ISI in the processed signal using TR. In the proposed method, FMT modulation is exploited to modulate information symbols onto separate subcarriers with high spectral containment and TR technique, as well as adaptive equalization is adopted at the receiver to suppress ISI and noise. The performance of the proposed method is assessed through simulation and real data from a trial in an experimental pool. The proposed method was compared with the TR acoustic communication using SC modulation with the same spectral efficiency. Results demonstrate that the proposed method can improve the performance of the TR process and reduce the computational complexity of adaptive equalization for post-process.

IEEE Sensors Journal, 2015

Unsynchronized localization systems based on the measurement of time (difference) of arrival requ... more Unsynchronized localization systems based on the measurement of time (difference) of arrival require reliable time stamps of the received signal. Noise, frequency shifts, and echoes disturb the signal and induce measurement errors of the time stamp, which leads to localization errors. Furthermore, the line of sight (LOS) signal has to be distinguished from the echoes to avoid false signal tracking. The proposed method combines the information of an ultrasound transmission with the measured time stamp and estimates the identifier. In our approach, the ultrasound transmission system uses phase-shift keying to modulate the signal. The received symbols and the time stamps are tracked and fused by the Kalman filter to increase the signal-to-noise ratio of the fused symbols and improve the validity of the decoding. Hence, the bias of the received symbols is tracked and the tracking allows to distinguish between the LOS signal and the echoes. As a result, the data fusion reduces the packet error rate from 70% at a distance of 21 m to 4.5%. Moreover, the median error of the localization is reduced from 7 to 4.6 cm.

2011 IEEE Sensors Applications Symposium, 2011

ABSTRACT