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Air coupled ultrasonic transducers: Design and applications

: Gebhardt, W.; Spies, M.; Arnold, W.

Maev, R.G.:
Acoustical Imaging. Vol.26: Proceedings of 26th Acoustical Imaging Symposium : held September 9 - 12, 2001, in Windsor, Ontario, Canada
New York, NY: Kluwer Academic Publishers, 2002 (Acoustical imaging 26)
ISBN: 0-306-47340-2
International Symposium on Acoustical Imaging <26, 2001, Windsor/Canada>
Conference Paper
Fraunhofer IZFP ()

Based upon piezoelectric composite materials, air-coupled ultrasonic probes with frequencies above 100kHz were developed. These probes have a bandwidth larger than 50% and we obtained a dynamic range than 100dB. The essential part of the probes is a piezoelectric composite (1-3-configuration) developed and fabricated at the IZFP. The piezoelectric composites (acoustic impedance 6 to 10 MRayl) are characterized by a high electro-acoustic coupling coefficient k2= 0.7,better acoustic matching to a gas or a liquid compared to a piezoelectric ceramic (acoustic impedance 35 MRayl) and a low mechanical quality factor. To further improve the efficiency of air-coupled probes, pressurized air-shoes and traveling wave transducers are in current development.