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Design of a MEMS-based ultrasonic pulse-echo system

Auteur(s) : C. Domingues, S. Mir, L. Rufer

Doc. Source: 18th Conference on Design of Circuits and Integrated Systems (DCIS'03)

Publisher : IEEE

Pages : 623-628

This paper describes the design of a micromachined ultrasound transducer (MUT). This microsystem is used in a pulseecho application and it can work as emitter and receiver of ultrasonic signal. The device is fabricated in a 0.8_m CMOS bulk micromachining process, integrating in the same chip a suspended membrane and the associated interface electronics. The membrane is thermally actuated at its resonance frequency (40 kHz) during emission. During reception, a piezoresistive bridge placed on the membrane is used for monitoring the membrane deflections. The resonance frequency of the MEMS is tuned to the emitted frequency by keeping the membrane at the same temperature, achieving then maximum sensitivity. The advantage of this design with respect to capacitive transducers is given by its simplicity: the employment of only one element of the dynamic structure simplifies the design considerations in terms of mechanical stability and membrane damping as well as the fabrication process.