A High Bandwidth PMUT Based on X-Cut Single-Crystal Lithium Niobate for Underwater Communication

With the advancement of Internet of Underwater Things (IoUT), underwater intelligent vehicles are becoming more compact, clustered, and diverse, leading to a significant rise in the demand for underwater communication. Rely on the minimal attenuation of acoustic signals underwater and the long transmission distances achievable, acoustic communication has garnered significant attention. However, the lack of thorough investigation into the correlation between device characteristics, such as bandwidth, signal-to-noise ratio (SNR), and material properties, hinders the development of high-speed and accurate data transmission underwater. In this study, we designed and fabricated the X-cut single-crystal lithium niobate (LiNbO3 or LN) piezoelectric micromachined ultrasonic transducer (PMUT) with a lateral-field-excitation (LFE) structure. The investigation focused on the correlation between piezoelectric properties of materials and device performance under different in-plane orientations. Underwater experimental results demonstrate that the LN PMUTs achieve a wide bandwidth of 2.31 MHz (70.1% at −6 dB) and possess a high SNR of 81 dB. Furthermore, the LN PMUTs efficiently detect signals encoded in the 2-amplitude shift keying (2ASK) protocol at a transmission rate of 650 kbit/s at 1.25 m. These findings indicate that LN PMUTs, with their high bandwidth and SNR, can provide technical support for efficient communication in underwater electronic devices.