@inproceedings{KonetzkeRutschHoffmannetal., author = {Konetzke, Eric and Rutsch, Matthias and Hoffmann, Maik and Unger, Alexander and Golinske, Ren{\´e} and Killat, Dirk and Ramadas, Sivaram Nishal and Dixon, Steve and Kupnik, Mario}, title = {Phased array transducer for emitting 40-kHz air-coupled ultrasound without grating lobes}, series = {Proceedings, IEEE International Ultrasonics Symposium (IUS), 21 Oct - 24 Oct 2015}, booktitle = {Proceedings, IEEE International Ultrasonics Symposium (IUS), 21 Oct - 24 Oct 2015}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2015.0019}, pages = {4}, language = {en} } @inproceedings{HoffmannUngerJaegeretal., author = {Hoffmann, Maik and Unger, Alexander and J{\"a}ger, Axel and Kupnik, Mario}, title = {Effect of transducer port cavities in invasive ultrasonic transit-time gas flowmeters}, series = {IEEE International Ultrasonics Symposium, Taipeh (Taiwan), 2015}, booktitle = {IEEE International Ultrasonics Symposium, Taipeh (Taiwan), 2015}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2015.0272}, pages = {1 -- 4}, language = {en} } @phdthesis{Hoffmann, author = {Hoffmann, Maik}, title = {Untersuchung zur Realisierbarkeit eines Ultraschalldurchflussmessger{\"a}tes mittels schmalbandiger Ultraschallwandler}, address = {Cottbus}, pages = {xv, 130}, abstract = {Schmalbandige Ultraschallwandler versprechen durch ihre Anpassung an Gase deutlich h{\"o}here Schalldr{\"u}cke und eine bessere Sensitivit{\"a}t und somit f{\"u}r den Einsatz in Gasultraschalldurchflussmesssystemen einen alternativen Ansatz. Insbesondere die, f{\"u}r die Verwendung in Gasen neuen, Capacitive Micromachined Ultrasonic Transducers (CMUTs) bieten sich an, da sie auch in rauen Umweltbedingungen eingesetzt werden k{\"o}nnen. Damit bieten sie einen neuen Ansatz zur Verwendung in Ultraschalldurchflussmessger{\"a}ten f{\"u}r Gase. Bisher wird beim Einsatz von Ultraschallwandlern mit breitbandigen Typen gearbeitet und mittels Impulsen und Korrelation die Laufzeit bestimmt. Diese Verfahren sind nicht f{\"u}r schmalbandige Wandler geeignet. Zur optimalen Umsetzung der Analyse wird eine Bestimmung der Richtcharakteristik der Ultraschallwandler, der Schallausbreitung im Flowmeter und m{\"o}glicher St{\"o}rger{\"a}usche durchgef{\"u}hrt. Aus diesen Ergebnissen wird unter anderem ein mehrkanaliges Durchflussmessger{\"a}t aufgebaut, welches eine optimale Schallausbreitung ohne eine Beeinflussung der Str{\"o}mung erm{\"o}glicht und nur einen Ultraschallsender ben{\"o}tigt. Anhand von Simulationen und Messungen an zwei aufgebauten Durchflussmessern werden im Rahmen dieser Arbeit verschiedene Verfahren untersucht, die es erm{\"o}glichen, bei extrem schmalbandigen Wandlern die Laufzeit zu bestimmen. Es kristallisieren sich zwei Continuous Wave (CW)-Verfahren heraus, die einen Einsatz dieser Wandler erm{\"o}glichen. Die Phasenbestimmung mittels 6-Tor-Methode sowie ein in einem Field Programmable Gate Array (FPGA) umgesetztes Z{\"a}hlverfahren liefert kontinuierlich die Phasenverschiebung bzw. Laufzeit der Signale, aus der die Str{\"o}mungsgeschwindigkeit bestimmt werden kann. Im Vergleich zu einem Str{\"o}mungsmesser mit einer Prandtlsonde zeigen beide Verfahren qualitative ebenb{\"u}rtige Ergebnisse bei signifikant h{\"o}herer Effizienz.}, language = {de} } @inproceedings{UngerKonetzkeRutschetal., author = {Unger, Alexander and Konetzke, Eric and Rutsch, Matthias and Hoffmann, Maik and Ramadas, Sivaram Nishal and Dixon, Steve and Kupnik, Mario}, title = {Versatile air-coupled phased array transducer for sensor applications}, series = {IEEE Sensors 2015, Busan, South Korea}, booktitle = {IEEE Sensors 2015, Busan, South Korea}, publisher = {IEEE}, doi = {10.1109/ICSENS.2015.7370187}, pages = {1 -- 4}, language = {en} } @inproceedings{HoHoffmannUngeretal., author = {Ho, Min-Chieh and Hoffmann, Maik and Unger, Alexander and Park, Kwan Kyu and Kupnik, Mario and Khuri-Yakub, Butrus T.}, title = {CMUTs in Permanent Contact Operation for High Output Pressure}, series = {Proceedings, ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems and ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels}, booktitle = {Proceedings, ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems and ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-5690-1}, doi = {10.1115/IPACK2015-48733}, pages = {6}, language = {en} } @inproceedings{GusevaHoffmannUngeretal., author = {Guseva, Anastasia and Hoffmann, Maik and Unger, Alexander and Zulk, Silvia and El Amien, Mohamed Balla and Sarradj, Ennes and Kupnik, Mario}, title = {Ultrasonic transducer characterization in air based on an indirect acoustic radiation pressure measurement}, series = {IEEE International Ultrasonics Symposium (IUS), 21-24 October 2015, Taipei, Taiwan}, booktitle = {IEEE International Ultrasonics Symposium (IUS), 21-24 October 2015, Taipei, Taiwan}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2015.0333}, pages = {1 -- 4}, language = {en} } @inproceedings{GolinskeHoffmannKonetzkeetal., author = {Golinske, Ren{\´e} and Hoffmann, Maik and Konetzke, Eric and Unger, Alexander and Rutsch, Matthias and Kupnik, Mario}, title = {Diffraction loss calculation based on boundary element method for an air-coupled phased array}, series = {Proceedings IEEE International Ultrasonics Symposium Proceedings, 2015}, booktitle = {Proceedings IEEE International Ultrasonics Symposium Proceedings, 2015}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2015.0375}, language = {en} } @inproceedings{UngerHoffmannHoetal., author = {Unger, Alexander and Hoffmann, Maik and Ho, Min-Chieh and Park, Kwan Kyu and Khuri-Yakub, Butrus T. and Kupnik, Mario}, title = {Finite element analysis of mechanically amplified CMUTs}, series = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, booktitle = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2013.0074}, pages = {287 -- 290}, abstract = {We introduce the possibility of improving a single-cell capacitive micromachined ultrasonic transducer (CMUT) for air-coupled ultrasound by simply adding a hollow conical-shaped structure (horn) on top of the CMUT plate. The main objective is to improve both transmit and receive sensitivity by lowering the center-to-average displacement ratio, which for bending plate operated devices inherently is limited. In addition, for receive mode the force generated from the impinging sound pressure wave is concentrated to the center of the plate, resulting in larger signals and, in contrast to piston-shaped plates, the horn has the advantage of only moderately increasing the modal mass of the structure. By using finite element analysis and first sound pressure measurements of our modified CMUT, we demonstrate that this idea is feasible and promising for air-coupled CMUTs operating at frequencies below 150kHz, as it has been been proven to be successful for commercially available piezoelectric - driven bending plate devices as well.}, language = {en} } @inproceedings{HoffmannUngerHoetal., author = {Hoffmann, Maik and Unger, Alexander and Ho, Min-Chieh and Park, Kwan Kyu and Khuri-Yakub, Butrus T. and Kupnik, Mario}, title = {Volumetric characterization of ultrasonic transducers for gas flow metering}, series = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, booktitle = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2013.0336}, pages = {1315 -- 1318}, abstract = {The design of ultrasonic gas flowmeters requires a thorough three dimensional characterization of the acoustic sound field. For large pipe flowmeters, such as used for flare gas metering, the transducers are operated at frequencies ranging from 20 kHz up to 150 kHz. Thus, in this work we use a commercially available calibrated 1/8-inch microphone, mounted on a 3D positioning system for performing volumetric measurements in a volume of up to 1x1x1 m. By using proper corrections in terms of angular and free-field response of the microphone, the measurement system is efficient and delivers around 30000 measurements in about only eight hours. The data then is visualized in form of 3D figures or various slices to extract all relevant information. The system has been used to identify non-uniform velocity profiles in capacitive micromachined ultrasonic transducers (CMUTs), operating in permanent contact mode. Further, the system can be used to investigate the effect of various acoustic boundary conditions the transducers are facing when mounted inside transducer port cavities and it can be used for general model validation purpose.}, language = {en} } @inproceedings{RutschKonetzkeUngeretal., author = {Rutsch, Matthias and Konetzke, Eric and Unger, Alexander and Hoffmann, Maik and Ramadas, Sivaram Nishal and Dixon, Steve and Kupnik, Mario}, title = {Extending the receive performance of phased ultrasonic transducer arrays in air down to 40 kHz and below}, series = {IEEE International Ultrasonics Symposium, Taipeh (Taiwan), 2015}, booktitle = {IEEE International Ultrasonics Symposium, Taipeh (Taiwan), 2015}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2015.0095}, pages = {1 -- 4}, language = {en} }