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Item type:Publication, Access status: with files , Mobile-BAT - A novel ultra-low power wildlife tracking system(Multidisciplinary Digital Publishing Institute (MDPI), 2023-05-31); ; ; ; We introduce a novel ultra-low power system for tracking animal movements over long periods with an unprecedented high-temporal-resolution. The localization principle is based on the detection of cellular base stations using a miniaturized software-defined radio, weighing 2.0 g, including the battery, and having a size equivalent to two stacked 1-euro cent coins. Therefore, the system is small and lightweight enough to be deployed on small, wide-ranging, or migrating animals, such as European bats, for movement analysis with an unprecedented spatiotemporal resolution. The position estimation relies on a post-processing probabilistic RF pattern-matching method based on the acquired base stations and power levels. In several field tests, the system has been successfully verified, and a run-time of close to one year has been demonstrated.Publicationtype: Journal Article58 60 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A direction-of-arrival estimation system for UAV-assisted search and rescue: locating mobile phones to improve the survival chance of disaster victimsCollapsing buildings are, while not exactly common, still an issue. The causes are diverse and often region dependent. The most common cause of the large-scale structural failure of buildings is earthquakes. In countries less affected by earthquakes, explosions caused by gas leaks are the leading cause.Publicationtype: Journal Article35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Design of a High Linear, Frequency Selective VHF-Receiver with Low Phase Noise for a Passive Radar System(2022-09); ; ; A major challenge in designing receivers for a passive radar system is the high dynamic range between the received direct and the received echo signal. Moreover, other interfering signals that are generated in the receiver appear, which leads to a reduced total sensitivity. For passive radar with FM radio transmitters wideband receivers are mostly used. This paper shows a frequency selective, high linear heterodyne receiver for a FM passive radar with a coverage area from 88 to 108 MHz and an output frequency of 10.7 MHz.Publicationtype: Conference Paper32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , UAV-based Localization of Mobile Phones for Search and Rescue ApplicationsIn this work a system is proposed that utilizes an unmanned aerial vehicle (UAV) to search and rescue trapped victims using their mobile phones. The systems consists of two parts, a ground station (GS) and an airborne station (AS). The GS provides a downlink to the UAV, a GSM base station along with antenna equipment and a mobile network jamming device. By using a smart approach to block the synchronization sequences of all base stations in range, the mobile phones of the victims to be located are switching to an emergency fallback mode. In this mode the phones connect to the strongest base station in range, thus the one provided by the GS. By initiating a call to the corresponding phone the AS can localize it using direction-of-arrival detection with a 9-channel phase coherent receiver system.Publicationtype: Conference Paper35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A 9-Channel Phase Coherent Receive System for Direction of Arrival Estimation(2022-04); ; ; ; Collapsed buildings are a common occurrence after earthquakes, but are also commonly caused by gas explosions. The survival chance of buried victims is heavily dependent on the time it takes to locate and rescue them. This paper introduces a 9-channel phase coherent receive system intended for direction finding in search and rescue applications. The motivation for this system is to minimize the time necessary to locate the buried phones of victims. The design consists of an FPGA based digital system with high speed I/O for data acquisition and signal processing, as well as nine synchronized receivers each covering the entire target bandwidth. A high phase resolution is achieved down to very low input levels.Publicationtype: Conference Paper85 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A Light Weight 3x3 Switched Polarity URA Antenna and Receive System for Direction FindingMinimizing the time it takes to locate and rescue victims from building collapses is critical for their survival chance. This scenario causes a challenging environment for radio frequency based localization. This paper introduces a direction finding system based on a 3x3 uniform rectangular array with integrated polarization switching for multipath mitigation intended for search and rescue applications. It is shown that utilizing two polarizations can be used to reduce or eliminate ambiguities caused by multipath propagation. Further approaches to optimize localization ability are discussed.Publicationtype: Conference Paper47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Langzeit-Funklokalisierungsverfahren mit extrem energieeffizienten, miniaturisierten Mobilfunkloggern(2022); In the area of wildlife and species conservation and ecology, movement profiles are an important method for spatial and behavioral analyses. Research on the movement behavior of bats imposes high technical demands on appropriate tracking systems. The low weight and the photophobic behavior of European species implies a resource limitation and the necessity to have the energy required for the entire run time from the very beginning, since energy harvesting (e.g. with solar cells) is not feasible. In recent years, several radio localization systems specifically tailored to bats have been published, which can be used to record precise flight movements and the social and hunting behavior of the animals. However, due to their functional principle, only limited ranges and run times can be realized, which makes them unsuitable for long-range migration analyses. This thesis introduces a novel radio localization method for bat migration analysis that, for the first time, provides position records with consistently high temporal resolution over one migration periode. The method is based on the detection of cellular base stations, whose locations are known a priori and which are used for position estimation. A key point of this work is the system design of a miniaturized cellular logger, which was realized as a software defined radio consisting of an integrated sub-GHz transceiver and an ARM Cortex-M4 microcontroller. For this purpose, a GSM stack optimized for real-time capability was implemented to detect GSM cells in the 900 MHz band and decode their BCCH. In addition to supplementary acceleration and temperature sensing, the logger has a functionality for recovery and data download via an 868 MHz radio interface. Ruggedly constructed with a fiber composite, the logger has a weight of 2.0 g with the form factor of a 1 Eurocent coin and achieved a measurement lifetime of 11.2 months with four measurements per day. The system was successfully deployed on bats in several field tests. For a two-week short-term deployment with a measurement interval of 10 minutes, the loggers were glued to animals of the species greater mouse-eared bats (Myotis myotis). The recorded data could be downloaded daily by radio in the roost and the movement behavior of the nocturnal excursions could be analyzed. For long-term migration analysis, the loggers were sutured to the skin of common noctules (Nyctalus noctula) and took four measurements per day. This method of attachment, which has been rarely used before, turned out to be insufficient, so only one logger could be recovered. However, its migration behavior could be reconstructed in detail with a previously unreached resolution.Publicationtype: Doctoral Thesis234 1342 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Signal Processing for Low-Power and Low-Cost Radar Systems in Bicycle Safety Applications(2022-01); ; ; ; In this publication a miniaturized low-power radar system is introduced that allows detection, tracking and measurement of motorized vehicles passing a bicycle rider. The main focus of this paper is to show a system that is responding with a situation adapted modulation to different measurement requirements while keeping power consumption and BOM cost to a minimum. This is achieved with using an integrated 60 GHz radar and a STM32 ultra-low-power microcontroller for the required signal processing.Publicationtype: Conference Paper67 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A 10 kHz to 6 GHz low-cost vector network analyzer(Copernicus Publications, 2021-12-17); ; ; This publication introduces a low-cost vector network analyzer with very large frequency range made of commercial off-the-shelf components. It utilizes two identical receivers and two directional bridges to allow for two fully bidirectional measurement ports. The design surpasses the performance of competing low-cost network analyzers in regards of dynamic range, frequency span and calibration capability.Publicationtype: Journal ArticleScopus© Citations 1 147 323 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Analysis of a Physically-Embedded Radar Sensor System(2021-04); ; ; ; This paper presents an embedded mm-wave FMCW-radar based sensor system designed to monitor the structural health of a wind turbine rotor blade. Special consideration is given to the evaluation of thermal performance and the possibility of correlating measurements with the current rotor blade orientation. The sensitivity of the sensor in its embedded state is analyzed and evaluated for system performance.Publicationtype: Conference Paper29