An Improved Lumped Element Model for Circular-Shape pMUTs

Abstract

This paper presents an improved lumped element model for clamped, circular-shape, piezoelectric micromachined ultrasonic transducers (pMUTs). A small signal equivalent circuit is developed to include electrical, mechanical, and acoustic domains, which are analyzed separately and combined with the associated couplings. For the first time, a two-term mode shape approach is adapted to reveal intrinsic and extrinsic properties of a pMUT, such as equivalent circuit parameters, input impedance, velocity, displacement, bandwidth, quality factor, directivity, and the on-axis pressure in the near and far field. These properties are compared with prior reports in the literature and exact solutions, as well as Finite Element Method (FEM) simulations. The errors relative to exact solution for all these properties are below 0.5%. These improvements in error are from 5x to about 3 orders of magnitude better than those of prior works. As such, the improved model could be helpful in design and simulation tools for pMUTs.

Efficient Modeling of Piezoelectric Micromachined Ultrasonic Transducers Using a Combination of Finite and Lumped Element Modeling

“…The stack is composed of 100 nm SiO 2 /1500 nm Si/200 nm Mo/900 nm AlN/200 nm AlCu/300 nm SiN. An equivalent circuit of a single diaphragm is derived using the approach presented in [1]. The imperfect anker stiffness is adjusted to match the finite element model.…”

Modeling a Fluid-Coupled Single Piezoelectric Micromachined Ultrasonic Transducer Using the Finite Difference Method

“…The present goal is to discuss the limits of each approach and identify their respective advantages and disadvantages. Many analytical models have been published, but the two oldest [12,46] have been used as the basis for assumptions applied in the more recent works [33,59,61,72]. We have therefore chosen to focus our comparison on the model from K. Smyth et al [46] and Perçin et al [4,12].…”

“…This approximation is clearly better than considering that PMUT works like a piston, particularly at high frequencies where the velocity distribution impacts the PMUT directivity. Pala et al [72] used the same method as Smyth except that a decomposition of quadratic-type functions was used instead of eigenfunctions of the plate equation.…”

“…This is the advantage (see Section 3.2) of having developed a numerical approach. However, it should be remembered from previous works, K. Smyth [46] and Pala [72], that when calculating radiation impedances, it is preferable to take plate deformation into account, particularly for the determination of the elementary directivity acoustic field but also the acoustic mutual impedances matrix between PMUTs. Though it is not further covered in this paper, additional investigations indicated that the type of pressure application and its distribution along the plate impact the cutoff frequency value as well.…”

Numerical Study of Acoustic‐Electric Signal Conversion for GIS Discharge Detection and Structure Optimization for pMUT

“…As a result, the material of the piezoelectric layer is an important factor afecting pMUT performance. In addition, the element size, materials, and integration process of the piezoelectric layer, elastic support layer, and electrode layer will further afect the mechanical properties of pMUT, which will infuence its multiple response performances [11]. Terefore, it is important to design sensors with special structures to meet specifc performance requirements for pMUT applications.…”