This work presents a distance measurement system for the localization of passengers in the sea in case of a ship sinking emergency. By applying the radar principle together with a switched injection-locked oscillator (SILO) as an active reflector the distance to a passenger can be determined through continuous measurement of the roundtrip time of flight of a chirp signal. The system is based on a concept previously published in [Wie03, VG08, Str14] and for the first time is designed in the 2,45GHz ISM frequency band. Criteria for the design of SILOs formulated in [Str14] were applied and verified for the first time at an operating frequency of 2,45GHz. The designed circuits were manufactured in a SiGe BiCMOS technology. The SILOs are based on a commonbase Colpitts and cross-coupled topology and exhibit the lowest published input referred noise power of −79 dBm. The output power is 12,3 dBm and 12,6 dBm, respectively. The efficiency of the cross-coupled as well as Common-Base Colpitts SILO is 26%. The theory of a SILO was extended towards the influence of interfering signals and the modulation signal. An interfering signal influences the starting behavior of a SILO in a way that a distance measurement leads to incorrect results. It was shown that interfering signals in the ISM frequency bands of 868MHz, 2,4GHz and 5,8GHz don’t allow correct distance measurements due to their high output power. Therefore, it is recommended to use an operating frequency of the SILO that is not close to any possible interfering signal, like the ISM band at 24GHz. This minimizes measurement errors and enables a more accurate distance measurement. Furthermore, it was shown that a phase coherent start of oscillation to any received signal is influenced by the modulation signal. For injection powers below −40 dBm the oscillator does not start its oscillation due to the injected signal, but to the modulation signal itself. This disables exact distance measurements. Through the use of a modulation capacitor at the base of the tail current source this effect can be minimized and the input referred noise power of the oscillator can be improved. The functionality of the distance measurement system was also verified for both SILO topologies. The range of the system in the best case scenario with a Common-Base Colpitts SILO was 120m, at an accuracy of 53 cm and a precision of 42 cm. All results regarding accuracy and precision exceed the specification of the system.

Die vorliegende Arbeit untersucht, wie die genaue Kenntnis der Sende- und Empfangsschallfelder eines Ultraschallwandlers zur Entwicklung neuer Meßverfahren genutzt werden kann. Insbesondere werden dargestellt: - ein neuartiges, nichtscannendes Verfahren zur Bestimmung der Krümmung eines Reflektors, basierend auf der Analyse der Wellenfrontkrümmung reflektierter Schallfelder - ein neuartiges, nichtinvasives Verfahren zur Bestimmung der Schallgeschwindigkeit in einer Flüssigkeit durch Auswertung der Echosignale von im Ausbreitungsmedium vorhandenen Streupartikeln und - ein Verfahren zur Wandlercharakterisierung durch Messungen in Fluiden mit Streupartikeln, sowie verschiedene Zuordnungen von Schallfeldmerkmalen zu spezifischen Eigenschaften eines Ultraschallwandlers. Im Zusammenspiel von Simulation und Experiment konnten die Funktionstüchtigkeit aller Meßverfahren nachgewiesen und vielversprechende innovative Ansätze für zukünftige Entwicklungen angeregt werden: 1. Das nichtscannende Verfahren zur Krümmungsmessung erlaubt bei guter Justage eine Krümmungsbestimmung von Reflektoren mit Radien zwischen 6 und 11 mm mit einer Unsicherheit von ungefähr 0,5 mm. In Kombination mit herkömmlichen scannenden Verfahren bietet es Ansätze zur präzisen Größenbestimmung von Fehlern in der zerstörungsfreien Prüfung. 2. Das Verfahren zur nichtinvasiven Schallgeschwindigkeitsmessung erlaubt eine Bestimmung von Schallgeschwindigkeiten mit einer statistischen Meßunsicherheit von 0,1 %. Mögliche Weiterentwicklungen zur Messung der Schallgeschwindigkeit mit örtlicher Auflösung und zur Gewinnung neuer Diagnosemöglichkeiten in Metallurgie (nichtinvasive Charakterisierung von Mischungsvorgängen) und Biomedizintechnik (nichtinvasive Temperaturmessung in Körpergewebe zur Überwachung der Hyperthermiebehandlung, Gewebecharakterisierung) werden erläutert. Aus verschiedenen bekannten sowie einem neuartigen, leicht anwendbaren Meßverfahren werden neue Schlüsse gezogen a) zur Bestimmung der akustisch effektiven Elementgröße von Wandlerelementen mittels Schallfeldmessungen, b) zur Qualitätssicherung im Hinblick auf Schallkopfasymmetrien und c) zur Verbesserung von Schallfeldsimulationen. / The current thesis explores how the precise knowledge of the sending and receiving sound fields of an ultrasonic transducer can contribute to the development of novel measuring techniques. Emphasis is placed on: - a novel, non-scanning method for the determination of the curvature radius of a spherical reflector, based on the analysis of the wave front curvature of the reflected sound field, - a novel non-invasive method for sound velocity measurements in fluids using the echo signals from scattering particles, and - novel conclusions on how to use well-known sound field measurement methods for transducer characterisation, as well as an introduction to a novel easy-to-use method for transducer characterisation exploiting the echo signals from scattering particles. Proof of concept is shown for all methods by simulation and measurement, and different promising improvements for further techniques are suggested: - The non-scanning method for curvature measurements makes it possible to determine reflector radii between 6 and 11 mm with an uncertainty of about 0.5 mm, provided that there is a good reflector alignment. In combination with conventional methods, a novel approach for the determination of the size of discontinuities in non-destructive testing is outlined. - The method for non-invasive sound velocity measurements allows the determination of sound velocity in homogeneous fluids with a statistical uncertainty of 0.1 %. Future improvements are suggested to allow sound velocity measurements with local resolution, which enables novel approaches for metallurgy (non-invasive characterisation of mixing processes) and biomedical engineering (non-invasive temperature control for hyperthermia treatment, tissue characterisation). - New conclusions are drawn based on well-established and a novel easy-to-implement measurement method regarding a) the determination of the acoustically effective element size of transducer elements, b) transducer asymmetries, thereby improving quality control, and c) the improvement of sound field simulations.