An experimental and computational study of beam-steering of parametric array

A parametric array is a nonlinear conversion process that can generate a highly directional sound beam with a small aperture. It is expected that electrical beam steering of directional sound beams generated by the parametric array may be useful in many applications such as ultrasonic raging sensors or directional loudspeakers in air. One of the major issues of beam steering of the parametric array is to precisely predict the steered difference frequency wave field in the medium. In this study, beam steering of the parametric array is computed by using a time-domain numerical code that solves the Khokhlov-Zabolotskaya-Kuznetsov equation. Since it is impossible to compute the exact difference wave field due to a complex primary source distribution in the medium, a simplified numerical model is proposed. The computed result is compared with the experimental result. For experimental study, 16-channel piezoelectric micromachined ultrasonic transducer array, which consists of two resonant type unit drivers to generate bi-frequency primary waves (f1 = 100 kHz and f2 = 140 kHz), was designed, fabricated, and tested. The beam patterns of the primary and difference frequency waves were measured and compared with the computed result while applying complex weighting to each channel. [Work supported by ADD (UD130007DD).]