The paper considers the optimization of a Hidden-Markov Model (HMM) based method for the generation of averaged motion sequences. To create averaged motion sequences, motion sequences of different test persons were originally recorded with a motion capture system (MoCap system) and then averaged using an HMM approach. The resulting averaged data sets, however, partly showed serious motion artifacts and uncoordinated intermediate movements, especially in the extremities. The aim of this work was to combine only movements with similar courses in the extremities by a suitable cluster analysis. For each test person, model body descriptions of 21 body elements are available, each of which is represented in three-dimensional time series. For optimization, the MoCap data are first compared using time warp edit distance (TWED) and clustered using an agglomerative hierarchical procedure. Finally, the data of the resulting clusters are used to generate new averaged motion sequences using the HMM approach. The resulting averaged data can be used, for example, in a simulation in a multilevel biomechanical model. © 2021 European Signal Processing Conference, EUSIPCO. All rights reserved.

Performance of systems for optical detection depends on the choice of the right detector for the right application. Designers of optical systems for ranging applications can choose from a variety of highly sensitive photodetectors, of which the two most prominent ones are linear mode avalanche photodiodes (LM‐APDs or APDs) and Geiger‐mode APDs or single‐photon avalanche diodes (SPADs). Both achieve high responsivity and fast optical response, while maintaining low noise characteristics, which is crucial in low‐light applications such as fluorescence lifetime measurements or high intensity measurements, for example, Light Detection and Ranging (LiDAR), in outdoor scenarios. The signal‐to‐noise ratio (SNR) of detectors is used as an analytical, scenario-dependent tool to simplify detector choice for optical system designers depending on technologi-cally achievable photodiode parameters. In this article, analytical methods are used to obtain a uni-versal SNR comparison of APDs and SPADs for the first time. Different signal and ambient light power levels are evaluated. The low noise characteristic of a typical SPAD leads to high SNR in scenarios with overall low signal power, but high background illumination can saturate the detec-tor. LM‐APDs achieve higher SNR in systems with higher signal and noise power but compromise signals with low power because of the noise characteristic of the diode and its readout electronics. Besides pure differentiation of signal levels without time information, ranging performance in LiDAR with time‐dependent signals is discussed for a reference distance of 100 m. This evaluation should support LiDAR system designers in choosing a matching photodiode and allows for further discussion regarding future technological development and multi pixel detector designs in a com-mon framework. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Especially in hospital entrances, it is important to spatially separate potentially SARS-CoV-2 infected patients from other people to avoid further spreading of the disease. Whereas the evaluation of conventional laboratory tests takes too long, the main symptoms, fever and shortness of breath, can indicate the presence of a SARSCoV-2 infection and can thus be considered for triage. Fever can be measured contactlessly using an infrared sensor, but there are currently no systems for measuring the respiration rate in a similarly fast and contactless way. Therefore, we propose an RGB-camera-based method to remotely determine the respiration rate for the triage in hospitals. We detect and track image features on the thorax, band-pass filter the trajectories and further reduce noise and artefacts by applying a principal component analysis. Finally, the respiration rate is computed using Welch’s power spectral density estimate. Our contactless approach is focused on a fast measurement and computation. It is especially adapted to the use case of the triage in hospitals by comprising a face detection which is robust against partial occlusion allowing the patients to wear face masks. Moreover, we show that our method is able to correctly determine the respiration frequency for standing patients despite considerable body sway. Copyright © 2021 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

After the introduction of ballistocardiography (BCG), there were various approaches and procedures with partly very different results in measurements and in the evaluation of the measurement results. Thus, BCG could not prevail against ECG. In the meantime, the focus has turned away from diagnostic to monitoring approaches and thus BCG, which derives mass shifts from cardiac and respiratory activity, is used in many new biosignal processing systems. To support the development of BCG based systems, a dedicated mass-based approach to modeling the cardiovascular and respiratory system including numerical values for the simulation parameters and evaluation methods will be presented. © 2021 IEEE.

In this paper a novel approach to measure currents noninvasively in a multi-conductor cable with conductor level resolution is presented. The measurement is based on an evaluation of the magnetic field outside the cable. A sensor-device based on this approach can be installed without removing any part of the isolation, separating the conductors inside the cable or even turning of connected electrical consumers. It is therefore considered noninvasive. Based on this approach a sensor-device is developed and tested. A maximum measurement deviation of 4 percent is achieved. © 2021 IEEE.

Signal processing, pattern recognition as well as modelling and simulation require a large amount of reference data, both for the development of new methods and for their evaluation. Depending on the application, the availability of databases is rather low. In the field of biosignal processing with a focus on the functionalization of furniture for nursing and hospital facilities, a database from a motion capturing system (MoCap), and a method to generate averaged human motion sequences was presented in subsequent works by our research group. Evaluations revealed that the averaged motion sequences partly contain artifacts caused by the averaging and thus are not directly usable. To use the averaged motion sequences e.g., in simulation tasks, this paper presents an extension with kinematic methods to combine averaged motion sequences and to suppress and thus optimize inappropriate motion artifacts by error correction. To check whether the results are usable after the processing steps, four evaluation criteria are proposed. The evaluation of the resulting motion sequences shows that sequences are generated which do not fully correspond to human motion sequences but are well suited for simulation tasks. © 2021 by Walter de Gruyter Berlin/Boston.

Commonly used blood pressure measurement devices have noticeable limitations in accuracy, measuring time, comfort or safety. To overcome these limitations, we developed and tested a surrogate-based, non-invasive blood pressure measurement method using an RGB-camera. Our proposed method employs the relation between the pulse transit time (PTT) and blood pressure. Two remote photoplethysmography (rPPG) signals at different distances from the heart are extracted to calculate the temporal delay of the pulse wave. In order to establish the correlation between the PTT values and the blood pressure, a regression model is trained and evaluated. Tests were performed with five subjects, where each subject was recorded fifteen times for 30 seconds. Since the physiological parameters of the cardiac system are different for each person, an individual calibration is required to obtain the systolic and diastolic blood pressure from the PTT values. The calibration results are limited by the small number of samples and the accuracy of the reference system. However, our results show a strong correlation between the PTT values and the blood pressure and we obtained a mean error of 0.18 5.50 mmHg for the diastolic blood pressure and 0.01 7.71 mmHg for the systolic pressure, respectively. © 2021 by Walter de Gruyter Berlin/Boston.

Industrial cleaning of textiles depend, as most cleaning processes, on the four parameters of the 'Sinner's Circle': chemicals, mechanics, temperature and time. State of the art washing machines are only able to measure the time and the temperature. The latter is arguably imprecise, as the temperature sensor is oftentimes located outside of the drum. For this reason, the machines are not able to work efficiently, as they use incorrect amounts of chemicals, heat and mechanical force, resulting in either insufficiently cleaned or stressed textiles. To increase the efficiency, an RFID-based approach is proposed to employ wireless sensors in the washing machine drum, which could be used to collect the data of interest. In order to overcome the severe influences from water, metal and the rotating drum, a broadband circularly polarized reader antenna, rotation symmetric contactless coupler and tag harvesting method are considered in this paper. The limitations and design considerations are discussed and first results are shown. © 2021 IEEE.

Emerging smart sensor systems are the main driver of innovation in many fields of application. A prominent example is condition-based monitoring and especially its subdomain fault diagnosis. The integration of advanced machine and deep learning-based signal processing into sensor systems enables new intelligent condition monitoring solutions. However, the data-based nature of machine and deep learning methods still impedes their applicability in many cases, due to a severe lack of data. In this paper, we introduce a new hybrid physics- and data-based framework aiming to solve the issue of small datasets for vibration-based fault diagnosis applied to rolling-element bearings. The framework combines a vibration simulation model and a neural network with embedded physics-based knowledge into a physics-guided neural network. Our approach aims to generate physically consistent data for the training of fault classifiers without extensive data acquisition. © 2020 IEEE.

Single-Photon Avalanche Diode (SPAD)-based 'Light Detection And Ranging' (LiDAR) systems often use the first photon measurement principle to acquire ranging information. While those systems provide accurate distance measurements, they can easily saturate in high background scenarios. Recent improvements in SPAD quenching circuit technology open up the opportunity for SPAD LiDAR systems to detect multiple photons while measuring with a single laser pulse, partially circumventing this challenge. The theoretical framework for the distribution of higher order single photon detections is presented and discussed how the sensor's typical quenching times influence it. Measurements with a SPAD circuitry capable of detecting multiple events in a single measurement are presented. Differences to first-photon and continuous detection implementations are discussed and advantages in high background light scenarios are shown. © 2020 IEEE.

Automotive and robotic applications demand three-dimensional (3D) imaging systems, that are reliable, small and low-cost. A promising technology to satisfy these demands are LiDAR-systems based on the direct time-of-flight principle. To greatly reduce the costs and footprint of current LiDAR-systems new compelling concepts are emerging. These concepts mainly differ in the used illumination techniques of the field-of-view (FOV). Micro-electro-mechanical systems (MEMS)scanners are replacing the bulkier and more expensive polygon mirrors, which were earlier used to deflect the laser beam and partially illuminate the FOV. In contrast to this approach the full illumination of the FOV with a single widened laser beam is used by the concept known as flash-illumination. The range performance of the direct time-of-flight principle is directly proportional to the emitted laser pulse power and is either limited by detector noise or background radiation. High-power near-infrared laser diodes are announced, which offer higher pulse peak power and shorter laser pulses. The high energy density of these laser sources can, however, be hazardous to the human eye. Therefore, the energy density of the laser pulse must be limited and classified according to the IEC 60825-1:2014. While this is particularly easy for Flash LiDAR-systems, a two-dimensional consideration is necessary to determine the accessible emission limits (AEL) for MEMS-based LiDAR-systems, which takes the time dependent scanning-motion of the mirror into account. This work presents a framework to describe and calculate the differences between the calculations of the AEL for Flash- and MEMS-based LiDAR-systems. To achieve this the framework incorporates the calculation of the two-dimensional pulse distribution based on the time dependent behaviour of the MEMS-scanner for the most commonly used one- and two-dimensional scanning-patterns. To further estimate and compare the performance of the LiDAR-systems this work describes an automotive and robotic application use case scenario, which are used to compare the performance for various performance metrices. © 2020 SPIE

In this paper, a 2D Luneburg lens is proposed to improve the Radar Cross Section (RCS) of dielectric resonator (DR) tags, which would be used for an indoor localization system at THz frequencies where the low RCS of the tag makes the detection against clutter signals difficult. A Luneburg lens made of PTFE is fabricated using milling technique based on metamaterial concept, and characterized using a Vector Network Analyzer (VNA). Three ceramic resonators with different resonance frequencies are placed at different positions in the lens focal area to test the performance of the lens. To prove the concept, the simulation and measurement have been performed at scaled frequencies in the 4.5-7 GHz range. The RCS improvement is found to depend on the lens dimensions and frequencies of operation. A Luneburg lens with a height of 35 mm and a diameter of 66 mm boosts the RCS by 18 dB at 6.2 GHz. © 2019 IEEE

Emotion recognition based on physiological parameters is a research field that pushes forward from lab settings to real-life investigations. Wearable devices facilitate this advance. However, these devices are still functionally limited compared to stationary medical devices. Our goal is to extend the capability of wearable devices by developing a method that measures the pulse transit time (PTT) locally. The PTT is an interesting parameter regarding emotion recognition. A method for local PTT measurement can be implemented using two photoplethysmography (PPG) sensors. However, this method is error-prone. In this paper, the physiological background that is presumably responsible for erroneous PPG-based PTT measurements is discussed. We present an algorithm that is capable to handle the derived physiological effects. The algorithm analyzes and compares the two PPG-signals to adapt to time-varying physiological effects. By using this algorithm, calculating and analyzing of the local PTT in the context of emotion recognition become possible. A study ( {n} = {40} ) to test the algorithm and investigate the usefulness of local PTT analysis for emotion recognition in combination with other physiological signals was conducted. PTT-based parameters, which were derived from the frequency domain of the signal, showed a statistically significant ( {p} < {0.05} ) difference between induced emotional states, if calculated by the developed algorithm. Our findings indicate that parameters derived by our method are significantly affected by emotional stimuli. We suggest that this method can be used to advance emotion recognition investigations in real life as it can potentially be integrated into a single wearable device. © 2001-2012 IEEE.

For many RFID applications it is desirable to get more information about an item than the unique ID, e.g. the position of a unique item often is of great interest. In this paper we present first simulation results of a novel method for measuring the distance between a reader and commercial off-the-shelf tags. This implies that the communication between a reader and a tag or a bulk of tags is not influenced or interrupted by this novel distance measuring method. It is expected to achieve a distance measuring accuracy of about 1% referred to the maximum communication distance between a reader and a tag. Additionally to the state-of-the-art RFID communication principle, which uses a well-known amplitude modulated (amplitude modulated due to the data transmission from reader to tag) RFID carrier, this novel measuring method uses an overlaid phase modulation. For the measuring principle to work it is important that the wavelength corresponding to the data rate of the phase modulation is not higher than twice the distance between reader and tag. If this condition is truly fulfilled, the phase information of the phase modulated signal will be clearly corresponding to the distance between reader and tag. The reader transmits the phase information to the tag which is returned to the reader due to the backscatter modulation. In a coherent reader structure the phase difference between the transmitted and received baseband signal can be used to calculate the distance from reader to tag. This distance calculation could be realized by correlation. Therefore the cross-correlated of the transmitted and received phase information can be subtracted from the auto correlation of the transmitted phase information. In case of this the distance can be calculated. © 2019 IEEE.

Motion capture systems or MoCap systems are used for game development and in the field of sports for the assessment and digitalization of human movement. Furthermore, MoCap systems are also used in the medical and therapeutic field for the analysis of human movement patterns. As examples gait analysis or examination of the musculoskeletal system and its function should be mentioned. Most application relate to a specific person and their movement or to the comparison of movements of different people. Within the scope of this paper an averaged motion sequence is supposed to be generated from MoCap data in order to be able to use it in the field of biomechanical modeling and simulation. For the averaging of individual movement sequences of different persons a Hidden Markov Model (HMM) based approach is presented. © 2018 author name(s).

The local measurement of pulse transit time in blood vessels can be implemented using photoplethysmography-based sensors. Therefore, at least two sensors must be placed such that the measured signals originate from the same artery. However, results from our previous research suggest that this kind of measurement does not always provide reliable results. We assumed that the inhomogeneous structure of the skin causes this behavior. Based on this theoretical background related experiments $(\mathbf{n}=\mathbf{8})$ were executed. The results suggest a signal distortion that strongly depends on the mounting position of the sensors. It can be shown that this distortion is presumably responsible for erroneous calculations of pulse transit time. © 2018 IEEE.

In this work the constant current stimulator of a new epiretinal implant is presented. It consists of a digital waveform generator device, which permits to modify the pulse pattern via a programming interface, a digital-to-current converter, which translates the digital waveform into current pulses with adjustable amplitude, and an output driver, which combines the function of an electrode multiplexer and a high voltage current source for driving large resistive loads. For each of those subcircuits the simulated performance and its designed layout is presented. © 2018 IEEE.

A miniaturized implantable multi-sensor system for cardiovascular monitoring of physiological parameters is presented. High accuracy pressure measurements within the vessel can be performed by a capacitive pressure sensor. Additional information about the patient, e. g., sudden movement, inclination or increased temperature can be obtained by additional sensor components such as an acceleration sensor and a temperature sensor unit. This information facilitates compensation of interferences for more accurate pressure measurements. A multi-functional ASIC enables, amongst others, sensor signal processing, power management and telemetric communication with extracorporeal electronics. Sensor chips, the multi-functional ASIC and passive components are assembled on a LTCC circuit board in which an antenna coil is integrated for telemetric energy and data transmission at a frequency of 13.56 MHz. In order to support further miniaturization, the implant shall be encapsulated with a stack of very thin and hermetic ceramics applied by ALD instead of using bulky metal housings. Further encapsulation with polymers, which can be functionalised with appropriate biomolecules, is necessary for a proper shape, a biocompatible interface to the surrounding tissue and, thereby, reduction of thrombogenicity. © 2018 Walter de Gruyter GmbH, Berlin/Boston.

A common procedure for the derivation of patient parameters is the use of measuring methods according to the so-called 'gold standard'. This may be e.g.The electrocardiogram (ECG) to derive the cardiac activity of a human. A great advantage of these methods is that they are widely accepted and clinically recognized and that they provide very good measurement-And diagnostic-results. A major disadvantage of these methods is often the complex measurement setup, e.g. by means of special electrodes attached to the skin or the need of a trained specialist. This is, of course, irrelevant in the field of emergency medicine, but if the general state of a person is to be monitored over a longer period of time e.g.To detect possible negative changes in the patient's condition at an early stage, such methods are rather unsuitable. Furthermore, a measurement setup used in clinical settings often puts the patient into a mode of discomfort. To avoid these disadvantages and to be able to perform a long-Term monitoring, the measurement should be preparation free by using e.g. functionalized furniture. Within the scope of the paper, a prototype of a preparation-free measurement setup based on a nursing bed is presented that is functionalized with load cell seat occupancy sensors from the automotive sector. Furthermore, the work carried out so far on the basis of the prototype is presented and discussed as an overview of our research activities in recent years. © 2017 IEEE.

In the field of signal processing, pattern recognition and also modeling and simulation, it is often necessary to use large data sets. These allow reliable, independent and test case spanning development of algorithms or even of complete systems. The data is usually taken from existing data sets such as TIMIT for speech recognition and processing or EPILEPSIAE to develop algorithms for epileptic seizure prediction, to give just two examples. Apart from the fact that some of these databases imply a considerable cost factor and thus are not accessible to all research groups, even greater problems arise if no data is available at all. In the field of speech recognition, this problem was solved more or less by creating databases. In the area of biosignal processing with a focus on the functionalization of furniture for care and clinical facilities, there is still a need for large data sets. This was also the case with biomechanical modeling of functionalized furniture, since up to now none or few data on the human movement sequences were available. In order to overcome this deficiency, the following paper presents a new database of motion patterns, which is intended to support the development of algorithms for motion detection as well as modeling biosignal processing. The database can be used and downloaded by any interested researcher for free. © EURASIP 2017.

There are several previously published approaches of measuring local pulse transit time (PTT). One of these approaches is to use two optical sensors based on photoplethysmography (PPG). However, little information about reproducibility in PPG based PTT measurement is available. Therefore, we performed a small sample size study (n = 5) to investigate quantitative criteria for reproducible PTT measurement. The inflection point as a characteristic feature of the pulse wave showed the most stabile results under varying conditions. Furthermore, we found that correlation between related pulse waves could be used as a threshold for signal quality. We suggest to implement a real-time operator feedback based on the found criteria to ensure reproducible PTT measurements. © 2017 IEEE.

Demographic change in the next few years will lead to a pronounced disparity in generation distribution. Hence there is a need to develop intelligent systems to support and maintain the autonomy of the elderly at home. A high priority in this case assumes the preparation-free acquisition of vital signs and patient parameters in long-term monitoring systems to detect early changes or deterioration in health. It is thus possible to initiate treatment of a disease at an early stage. One way to carry out a long-term monitoring of vital signs at home is based on the functionalization of furniture, for example, through the use of suitable sensors in chairs [1] and beds [2, 3] to derive various patient parameters. In addition to monitoring basic parameters, e.g. the heart rate and respiratory activity, it is also possible to access information regarding motion or sleep patterns by means of pattern recognition systems. In addition to the challenge of building a suitable pattern recognition system there is a need for corresponding training data to create reference patterns. Typically, the necessary sensor data for the reference pattern training is generated in time-consuming sessions with real people. In this paper, a novel approach is presented, which provides a multi-stage model to create artificial training or test data. The model can be used as a supporting tool in the development of posture recognition systems and to create artificial data for training and testing. © 2016 IEEE.

In medicine and other high-tech sectors, mobile RFID or sensor transponder systems are designed with high-Q antenna coils to increase the energy efficiency. Hence, the range of inductively coupled systems is improved; however, the bandwidth is decreased by 1 over Q. As a result, the reading performance is not limited by the energy supply, but instead by a high bit error rate. In this paper, we describe how the data detection in such narrow-band systems can be improved by a multilevel decoding scheme composed of an advanced maximum-likelihood receiver in the first stage and a soft Viterbi decoding scheme utilizing time variant reliability information in the second stage. An analysis of potential time-variant reliability information is given. The analysis relies on an underlying Bayesian model, which provides an a-posteriori probability indicating the reliability of the received input. As the final building block, a last decoding stage is discussed, which can be composed of a forward error correction that further exploits the reliability information at the second decoder output. Overall, the suggested system architecture results in a notable improvement of both bit and packet error rate, thus allowing the use of high-quality-factor antennas for efficient and reliable mobile RFID systems. © 2015/2016 - IOS Press and the authors. All rights reserved.

In this paper we present data on how powering passive sensor radio frequency identification (RFID) transponder can be performed more efficiently. We focused on the industrial, scientific and medical (ISM) band around 5.8 GHz. We investigated how different modulation indexes for amplitude shift keying (ASK) affect the rectification process. The rectifier configuration is Greinacher one with two HSMS2862 and the other with two PCC110 diodes from Avago and Powercast, respectively. The highest achieved power gain was 6.4 dB at a modulation index m of 100% compared to a continuous wave signal at an input power of -12.7dBm for the HSMS2862 rectifier. © 2016 The Authors.

This paper presents a novel wireless tear glucose level sensor for diabetes patients. The miniaturized sensor can be worn noninvasively under the eye lid. It is composed of a chronoamperometric glucose sensor and an ASIC set with integrated potentiostat and transponder circuits. Wireless energy and data transmission according to the passive transponder standard ISO18000-3 is used to power and readout the sensor. A special coil shape enables high comfort for the patient. High integration level is achieved by a combination of antenna and sensor electrode wires. A complete demonstrator system including ASIC and sensor fabrication as well as assembly was manufactured and the function is demonstrated. © 2014 The Authors. Published by Elsevier Ltd.

In this work an ultra-thin bendable imaging test structure is presented and experimental results are put forward. The deployed design and layout rules in order to achieve an independent operation on the applied mechanical stress are discussed. Moreover, experimental results of the optical characteristics of standard n+/p photodiodes on ultra-thin silicon chips embedded into a polyimide foil under several bending configurations are discussed and presented. © 2013 IEEE.

In this paper, theoretical as well as experimental results of the investigations on a bendable ultrathin Si monolithic CMOS image sensor are presented. The electro-optical behavior of a thinned flexible CMOS active pixel sensor for the application of uniaxial mechanical stress is theoretically and experimentally analyzed. The necessity of a correlated double sampling readout scheme to achieve a stress-independent operation is underlined. Optical as well as electrical characteristics of standard photodiodes on ultrathin silicon chips embedded into a polyimide foil under several bending configurations are discussed and experimental data are presented. Moreover, design rules for the stress-independent operation of a flexible ultrathin image sensor are given and the thinning and the encapsulation processes are shortly presented. © 2013 IEEE.

A modular, configurable, wearable bio-potential signal measurement diagnostic system is developed. The system is wirelessly configurable for multiple numbers of channels from 1 to 256 channels according to their field of applications. EEG (Electroencephalography), ECG (Electrocardiography), EMG (Electromyography) can be measured with the system by encapsulating in a cap, in a vest and in a hand sleeves respectively. Active dry electrodes with 19 Au-Pins are utilized. It achieves a high signal quality due to high special resolution. An electrode-bus containing eight of such dry electrodes is designed utilizing the modern hard-flex PCB concept so that it can be molded like an S and be placed on the area of measurement. A Meridian-ADC digitalizes the amplified analog signal with a 24-bit Δ∑-ADC. The central component of the system is an Islandcontroller, incorporating an AVR-μC and a Wi-Fi-module with an external patch antenna. © 2012 IEEE.

This paper presents a rapid-prototyping platform for test and implementation of new algorithms in RFID Systems. The platform offers the possibility to evaluate and test new approaches, in communications aspects in RFID systems, that can not be tested in state-of-the-art systems, due to hardware or standards limitations. This includes new radio architectures, source-/line-coding schemes, multiple access control algorithms and many other system elements that can not be accessed or changed in a RFID system. Two platforms are presented: one for algorithm development and a second one for product development. © 2012 IEEE.

For measurement problems with unknown fluids a new calibration-free volume flow measurement technique is developed. This measurement technique includes a controlled heat source associated with a minimum of two thermal sensors arranged downstream [5,6]. The heat source is used to generate a rectangular signal code [dT/dt] by injection of regulated thermal pulses into a flow line, the flow velocity being based on two measurands. Rapid changes in flow velocity are determined by the flow dependent variable (inversely proportional to the velocity) which is controlling the temperature of the filament. By analysis of the rising edge of the thermal signal of subsequent sensors the velocity can be measured less frequently but precisely and in unknown fluids (TToF) [6,7]. The combination of these two measurement techniques (hot wire and TToF) can be applied to both, liquids and gasses. © 2012 The Authors. Published by Elsevier Ltd.

By the use of sensor transponder technology, the therapy of heart failure can be significantly improved. Through continuous monitoring of the heart an optimal adaption of drug dosage is possible. First, the state of the art and examples of existing solutions are outlined. A novel sensor transponder system is presented that enables high read range and small antenna dimensions and thus allows direct implantation into the heart. © 2012 IEEE.

The authors report on a novel linear time-invariant (LTI) modeling of a flow sensor system based on thermal Time-of-Flight (TOF) principle by using pulsed hot wire anemometry. Thermal heat pulses are electrically generated at the hot wire centered in a pipe, carried along by the fluid in flow direction, and detected at several positions downstream. The flow sensor consisting of a hot wire and several temperature sensors is entirely regarded as an LTI system which is characterized by the fluid velocity, the fluid media and some heat transfer effects. Hence, a mathematical model with thermodynamic and fluid mechanical parameters is built. The thermo-fluid dynamic step and impulse responses of the hot wire are analyzed with respect to their signal parameters like rise and fall time and referred to the parameters of thermodynamics and fluid mechanics. The flow velocity and flow media are determined by signal analysis of the hot wire and by the thermo-fluid dynamic TOF measurement. © 2012 IEEE.

For measurement problems with unknown fluids a new calibration-free volume flow measurement technique is developed. This measurement technique includes a discontinuous heat source associated with a minimum of two thermal sensors arranged downstream. The heat source is used to generate a signal code [dT/dt] by injection of local thermal pulses into the flow line. The thermal sensors detect the time-dependent thermal gradients in the fluid at different positions. Herewith, the measurement technique aims at the determination of the flow velocity by ToF, with the particular advantage of applying to measurements of any fluids with unknown properties. The volume flow is determined by integrating the flow profile. © 2011 Published by Elsevier Ltd.

Design and measurement results of a CMOS 128 x 96 pixel sensor are presented, which can be used for three-dimensional (3D) scene reconstruction applications based on indirect time-of-flight (ToF) principle enabled by pulse modulated active laser illumination. The 40μm pitch pixels are based on the novel intrinsic lateral drift-field photodiode (LDPD) that allows for a 30ns complete charge transfer from the photoactive area into the readout node, and accumulation of signal charge over several readout cycles for extended signal-to-noise ratio (SNR). Distance measurements have been performed using a specially developed camera system. © 2011 IEEE.

Scannerless 3D-Time-of-Flight image sensors serve to acquire three-dimensional (3D) information of objects in a scene. This contribution is devoted to modeling and calibration of scannerless 3D-Time-of-Flight image sensors based on pulse modulation. After a short description we introduce a 3D image sensor model that includes system nonlinearities due to nonideal photodetectors and signal processing circuitry. This is followed by the model defined for the nonideal light source waveform. The influence of these nonlinearities on the sensor responsivity and, hence the distance calculation will be shown. Finally, based on our findings we propose an efficient calibration procedure for the proposed distance measurement system. © 2011 IEEE.

This article describes a pulsed thermal Time-of-Flight (TTOF) flow sensor system as two subsystems i.e., a pulsed-wire system and a heat flow system. The entire flow sensor is regarded system-theoretically as a linear time-invariant (LTI) system and is described by its transfer function or impulse response. The characterization of the thermo-fluid dynamic signals obtained by a pulsed-wire and by a heat flow is strived. Hence, the impulse response of both pulsed-wire and heat flow is analyzed according to the flow velocity. Experimental and theoretical results are compared in a flow velocity range in air between 0.1 m/s and 1.4 m/s. © 2011 IEEE.

A system-theoretical model of an air flow sensor based on the principle of pulsed thermal Time-of-Flight (TTOF) is described. The region of interest (ROI) in the pipe flow is regarded as a linear time-invariant (LTI) system with an input and output signal. Based on the experimental results the simulation model is created and applied for analysis of different input signals and system's responses with respect to the flow velocity. Experimental and simulated results are compared in an air flow velocity range between 0.1 m/s and 0.7 m/s. © 2011 IEEE.

In order to investigate whether the performance of microbolometer based heat imaging devices can be improved by excimer laser annealing, we performed several experiments on amorphous silicon layers. Samples with unstructured and structured amorphous silicon layers, which are fabricated with different doping concentrations using a plasma enhanced chemical vapor deposition process, are annealed with Krypton Fluoride excimer laser light at various energy densities. The samples are then electrically analyzed to verify laser annealing. They are also characterized in terms of their electrical conductivity, their temperature coefficient of electrical resistance and their 1/f noise as a function of energy density of the laser. The measurements are used to discuss whether excimer laser annealing is of use to improve microbolometer performance. A threshold value for the energy density at which recrystallization caused by laser irradiation occurs is observed to be 100 mJ/cm2 for both structured and unstructured samples. The temperature coefficient of electrical resistance decreases with increasing energy density from a value of 2%K-1 down to a value of approximately 0.9%K-1. © IEEE.

In this work a theoretical concept and simulations are presented for a novel lateral drift-field photodetector pixel to be fabricated in a 0.35 μm CMOS process. The proposed pixel consists of a specially designed n-well with a non-uniform lateral doping profile that follows a square-root spatial dependence. "Buried" MOS capacitor-based collection-gate, a transfer-gate, and an n-type MOSFET source/drain n floating-diffusion serve to realize a non-destructive readout. The pixel readout is performed using an in-pixel source-follower pixel buffer configuration followed by an output amplifier featuring correlated double-sampling. The concentration gradient formed in the n-well employs a single extra implantation step in the 0.35 μm CMOS process mentioned and requires only a single extra mask. It generates an electrostatic potential gradient, i.e. a lateral drift-field, in the photoactive area of the pixel which enables high charge transfer speed and low image-lag. According to the simulation results presented, charge transfer times of less than 3 ns are to be expected. © 2010 Elsevier B.V. All rights reserved.

Thermal flow measurement is currently based on the principle of heat energy displacement caused by a flowing fluid (mass flow measurement). The heat is induced by a continuous heating element immersed into the fluid. This kind of sensor is only applicable for fluids with known homogeneity properties [3]. The presented investigation is based on a discontinuous heating element using the pulsed Thermal Time-of-Flight principle (TTOF). The aim is to analyse a measurement technique which determines the flow velocity of any kind of fluid with unknown properties (volume flow measurement). The authors characterise the fundamentals of a measurement principle for determining the air velocity flow in a range from 0.1 m/s to 2 mls. Therefore, analysing the thermal transfer behaviour of a differential volume of flowing air in a pipe is crucial. For this purpose a sensor model consisting of a filament as heating element and a movable thermocouple as detection unit in a pipe construction under flow conditions is employed [6],[7]. The air flow model represents a thermal transmission system. A filament serves as a heating element and describes the input signal into the system. The output signal of the system is obtained by the thermocouple. Considering a linear time-invariant (LTI) system the impulse responses are measured for different flow velocities by applying an approximated Dirac delta function to the filament, and additionally the 3dB cut-off frequencies are obtained.