Microelectromechanical-systems-based parametric trans- mitting array in air—Application to the ultrasonic ranging transducer with high directionality

Abstract

Reduction of the transducer size decreases the efficiency of the secondary wave generation in the parametric transmitting array. To overcome this problem, MEMS-based transducer radiating high intensity sound is required in the parametric array. A high-performance PZT MEMS ultrasonic transducer composed of many small membrane-type radiator units was designed and fabricated by bulk micro-machining, and the secondary wave generated by the transducer was observed. This experiment proves that a MEMS-based parametric transmitting array is possible and applicable to some devices. A new ranging ultrasonic transducer with high directionality as an application was proposed because ultrasonic transducers generally need to be designed for high directionality to enhance the spatial resolution in the pulse-echo measurement in air. The 40-kHz difference tone, the measuring signal, was generated using 100- and 140-kHz primary tones by the PZT MEMS ultrasonic transducer. The difference tone had a half-power beam width of around 5 deg and a sound pressure level of over 85 dB at the peak. For the real application, higher sound pressure level should be achieved, and this will be included in the future work. [Research supported by MIC.]