Efficient Electrode Configuration for High-Sensitivity Performance with Minimal Analog Front-End Complexity

Abstract

This work presents a two-port “overpass” electrode design for a circular-shaped PMUT that reproduces the anti-phase inner/outer excitation effect of a traditional inner–outer electrode design with three ports. The proposed overpass connections create opposed local electric fields in a uniformly polarized piezoelectric thin film, enabling constructive charge addition while simplifying hardware. A circular-shaped PMUT cell with the proposed electrode design was fabricated and compared to an otherwise identical PMUT cells using the conventional inner/outer electrode layout. Air-coupled frequency response of the central velocity shows the overpass design delivers two times higher output sensitivity than conventional electrode design with only single-electrode excitation (inner-only or outer-only), while requiring only two ports. The approach also yields a substantial increase in electromechanical coupling (k), and adds no complexity to the thin-film stack and driving circuitry, improving scalability for high-channel arrays.