Abstract
This paper proposes a novel piezoelectric micromachined ultrasonic transducer (pMUT) with a proof mass under the central circular diaphragm to enhance transmission efficiency and fractional bandwidth (FBW) in liquid-coupled operation. Compared with the traditional pMUT, the proposed pMUT has advantages: (1) the resonance frequency of pMUT can be adjusted by proof mass; (2) a large ratio of third-order resonance frequency to first-order resonance frequency can be obtained by an additional proof mass under the circular diaphragm; (3) the mode shape of proposed pMUT changes from Gaussian-like to piston-like, which enables higher transmission sensitivity; (4) the FBW can be improved through a trade-off design. The characteristics of resonance frequency, output power, and FBW of pMUT with different proof mass are analyzed with a piezoelectric layer of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\mu \text{m}$ </tex-math></inline-formula> and a structural layer of 5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . In this work, the far-field sound pressure is 240.5 Pa/V in water, 49.5 Pa/V higher than the traditional pMUT, benefiting from the piston diaphragm movement. Furthermore, a 23% −6 dB FBW in water is demonstrated by theoretical analysis and parameter optimization. This work provides constructive advice for pMUT for better performance of transmission and resolution.
Highlights
Nowadays, ultrasound technology has been widely utilized in various fields, including medical imaging [1], nondestructive testing [2], and range-finding [3]
This paper proposes two new piston-like piezoelectric micromachined ultrasonic transducer (pMUT) by introducing a proof mass under the structure layer via simulations using COMSOL Multiphysics [13], and a standard finite element method (FEM) simulator is used for ultrasound propagation
A novel pMUT with proof mass is proposed in this paper
Summary
Ultrasound technology has been widely utilized in various fields, including medical imaging [1], nondestructive testing [2], and range-finding [3]. T. Wang et al presented a pMUT with piston-like motion by etching holes to improve transmitting sensitivity up to 73 nm/V at 2.31 MHz [6]. A. Guedes et al designed flexural suspended pMUT, showing a piston-like mode shape to improve output sound pressure [8]. In the ultrasonic transducer field such as therapeutics [9], spatial image resolution can be improved by transmitting and receiving shorter signals [10, 11], which proposes pMUT has a broadband characteristic. This paper proposes two new piston-like pMUTs by introducing a proof mass under the structure layer via simulations using COMSOL Multiphysics [13], and a standard finite element method (FEM) simulator is used for ultrasound propagation. The membrane remains flat during vibration by introducing a proof mass, resulting in a higher transmission sensitivity.
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