A Dual-Mode Parametric Acoustic Array Based on Air-Coupled Capacitive Micromachined Ultrasonic Transducer Array

Due to its low acoustic impedance, CMUT has good application prospects in parametric acoustic array field. An air-coupled CMUT array for directional emission of parametric acoustic array is introduced. The odd and even elements of the CMUT are connected with the external excitation circuit respectively to form two interlaced CMUT arrays, which can transmit two different frequencies on a single CMUT chip. We propose two operating modes to realize CMUT parametric array emission. In the first mode, the two sound signals emitted are always kept within the bandwidth of the CMUT. In the second mode, the two sound signals emitted have a larger energy and bandwidth than the first mode, which can generate low frequency sound waves with a larger frequency range. The results of simulation and experiment show that the difference frequency sound has high directivity, which achieves high directional sound emission by a small sensor array.