Microtech2010 2010

Frequency-Interleaved MEMS Ultrasound Transducer

S-J Chen, Y. Choe, E.S. Kim
University of Southern California, US

Keywords: MEMS ultrasound transducer, piezoelectric, frequency-interleaved, array of cantilevers

Abstract:

This paper presents an ultra-sensitive, broad-bandwidth ultrasound transducer based on frequency interleaving of resonant transducers. A large number of cantilever-like diaphragm transducers with piezoelectric ZnO films have been optimally connected in series and parallel, so that the sensitivity as a receiver and the sound output as a transmitter are measured to be about 30 times larger than those of a single transducer. The interleaving of the transducers not only increases the sensitivity but also broadens the useable bandwidth greatly. Each individual transducer’s sound pressure output was measured about 3 mm away from the transducer in an open field with a calibrated microphone. A single transducer was measured to produce 0.8Pa at 22kHz when it was driven with 75Vpeak-to-peak, while it was measured to have a receiving sensitivity of 100 V/Pa at 22kHz. When 16 such transducers were connected in parallel, both the sound output and the sensitivity were improved to 4Pa and 1.05mV/Pa, respectively. When 64 such transducers were connected in parallel, followed by 4 such sets in series, the sound output and the sensitivity were improved to 10Pa and 2.9mV/Pa, respectively. The useable bandwidth also was greatly improved.
 
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