Excitation design for air-coupled PMUTs for ring-down time reduction via time-domain equivalent circuit models

This paper presents an analytical approach to determine optimal offset signals for driving air-coupled piezoelectric micromachined ultrasonic transducers (PMUTs), aimed at effectively reducing ring-down time and broadening bandwidth without compromising transmission sensitivity. To achieve this, a time-domain equivalent circuit simulation platform for PMUTs is developed to quickly obtain and analyze the air-coupled PMUTs response. This platform facilitates to fast obtain the ring-down times for different excitation signals and allows continuous adjustment of parameters for the offset signal waveform. The optimal offset signal waveform is then identified by comparing ring-down times generated across various parameter configurations of offset signals in simulation. The effectiveness of these optimized offset signals achieved through the proposed method is confirmed experimentally with different driving signals. For example, for a PMUT cell with a radius of 360 μm, the ring-down time is decreased by at least 85.49 % with the obtained optimal offset signal for short-period driving signals, while the -6dB bandwidth of the PMUT is increased by more than 3.85 times with the obtained optimal offset signal for long-period driving signals. By suppressing ring-down, the proposed method minimizes the blind zone, sharpens the echo envelope, and enhances positioning accuracy for ultrasound applications. Furthermore, the developed simulation platform has significantly improved the efficiency of time-domain simulations for PMUTs research, providing a solid foundation for future system-level optimizations and studies on PMUTs applications.