Theoretical and Simulation Studies on Designing a Phase-Reversal-Based Broadband CMUT With Flat Passband and Improved Noise Rejections for SHM

Abstract

In the past two decades, capacitive micromachined ultrasonic transducers (CMUTs) have been greatly explored for applications in structural health monitoring (SHM); however, relevant theories about their broadband sense have not been investigated systematically. Therefore, broadband CMUTs have been specifically developed from the aspects of theory and simulation in this work. Based on these theoretical developments, we propose a new design of phase-reversal-based CMUT, which has a flat passband for broadband sensing and two stopbands at both sides for improved noise rejections. First, the expressions for the evaluation of the total output current and the sensitivity of a CMUT constituted of multiple cells are deduced from the theoretical spring-mass-damping model. Then, theoretical and simulation analysis on a CMUT combined with two different cells have revealed that reversing the current phase of one of these two cells can produce significant stopbands for rejecting the low-and high-frequency noises, which are useful not only for a CMUT in coarse vacuum (low pressure) but also a CMUT in the air (atmospheric pressure). Especially, for a CMUT in a coarse vacuum, this design can effectively build a passband among the resonant frequencies of each cell instead of compensating each other to zero. Finally, the genetic algorithm is adopted to design a broadband CMUT with a given passband in air, the results of which are verified by the frequency-and time-domain simulations concurrently. Our research work may produce a theoretical way for the design of broadband CMUTs with noise rejections.

Progress of MEMS acoustic emission sensor: a review

“…The lower electrode is a fixed electrode in contact with the solid surface to be tested, while the upper electrode is an extremely suspended resonant silicon film structure fixed onto the silicon layer through anchor points. When the external excitation signal acts on the CMUT, the resonant motion of the upper electrode changes the system capacitance (current), converting the acoustic signal into an electrical signal (Lu et al , 2022).…”

Phononic Crystal Coupled Mie Structure for Acoustic Amplification

“…Acoustic sensing-based monitoring systems are crucial in various applications, including structural health monitoring [1,2]. Acoustic sensor devices with high signal-to-noise ratio (SNR) are the key to acoustic monitoring systems [3,4]. Typically, traditional acoustic sensing methods rely on conventional electroacoustic sensor compositions [5][6][7].…”

Design and Finite Element Simulation of a Novel 3D-CMUT Device for Simultaneous Sensing of In-Plane and Out-of-Plane Displacements of Ultrasonic Guided Waves

“…More recently, researchers have started to design and fabricate CMUT-based sensors for structural health monitoring (SHM) applications. In the literature, by exploiting the conduction principle of capacitance changes, CMUT-based sensors for an acoustic emission (AE) application have been designed [13][14][15][16][17][18]. In 2006, D. Ozevin et al developed CMUT-based AE sensors that span the frequency range 100-500 kHz [13].…”