Geometry-Driven Design of Biaxial Piezoelectric Transducers for Acoustic Beam Steering

Biaxial driving is a promising alternative to conventional phased arrays for acoustic beam steering, utilizing orthogonal electric fields on a single piezoelectric element. However, achieving effective steering currently relies on empirical trial-and-error due to a lack of systematic design methodologies correlating transducer geometry with directional resonance behavior. In this work, the electromechanical and acoustic response of rectangular piezoceramic transducers is investigated through finite element simulations and experimental validation. The influence of the ratio between lateral dimension and thickness is examined across multiple geometries to evaluate its effect on the interaction between propagation and lateral resonance modes. We fabricated and characterized transducers with different lateral sizes and thicknesses to assess beam steering performance. The results show that acoustic steering is strongly dependent on geometry and can be systematically controlled. When the lateral dimension-to-thickness ratio lies between approximately 0.9 and 2, the fundamental propagation and lateral resonances converge while maintaining strong modal coupling, enabling efficient beam deflection. Under these conditions, steering angles of up to ±50° are achieved in both simulations and experiments. Outside this range, weaker modal interaction results in limited steering capability. These findings identify geometric scaling as a key design parameter for resonance engineering and provide a practical framework for the development of compact, electronically steerable piezoelectric transducers for ultrasound applications.