Direction of arrival estimation using asymmetric mode components of CMUTs

This paper investigates a novel method for estimating the direction of arrival of acoustic waves for ultrasound imaging arrays using the asymmetric mode components of CMUTs. The method is based on the correlation between the amplitude of resonant asymmetric mode of the CMUT membrane and the arriving angles of the acoustic waves. The asymmetric mode can be extracted by subtracting the signals received by a multielectrode CMUT cell and filtering in the frequency domain. FEM and acoustic field simulations show that the sensitivity of distinguishing the angles is higher using the asymmetric mode of a single CMUT cell than simple subtraction of neighboring cells. An experimental analysis was performed of a multi-electrode CMUT cell and asymmetric behavior was demonstrated.