Broadband 1–3 Piezoelectric Composite Transducer Design Using Sierpinski Gasket Fractal Geometry

Abstract

Wider operational bandwidth is an important requirement of an ultrasound transducer across many applications. In nature, it can be observed that several hearing organs possess a broad operating bandwidth by having a varying length scales structure. Moreover, conventional 1-3 piezoelectric composite transducers have been widely recognized for their wider bandwidth over their piezoelectric ceramic counterparts. In this paper, a novel 1-3 piezoelectric composite design using a fractal geometry, known as the Sierpinski Gasket (SG), is proposed in order to explore the potential of further extending the operational bandwidth and sensitivity of the transducer. Two equivalent 1-3 piezocomposite designs are compared to this end, one with a conventional periodic parallelepiped-shaped pillar structure and one with the SG fractal geometry, both theoretically, using a finite-element analysis package, and experimentally. The transmit voltage response and open-circuit voltage response are used to illustrate bandwidth improvement from the fractal composite design. Following the simulation results, a 580-kHz single-element transducer, utilizing the proposed SG fractal microstructure, is fabricated using a pillar placement methodology. The performance of the prototyped device is characterized and compared with a conventional 1-3 composite design, as well as with a commercial ultrasound transducer. In the one-way transmission mode, a bandwidth improvement of 27.2% and sensitivity enhancement of 3.8 dB can be found with the SG fractal design compared to an equivalent conventional composite design and up 105.1% bandwidth improvement when compared to the commercial transducer. In the one-way reception mode, the bandwidth improvement for the SG fractal design is 2.5% and 32.9% when compared to the conventional and commercial transducers, respectively.

Boundary element methods for acoustic scattering by fractal screens

“…where x l is the centre of the element T j,l . This is equivalent to approximating the testing integrals in the Galerkin equations (34) with a 1-point-per-element quadrature formula. The vector u containing the values of φ h j on each mesh element satisfies a square linear system Au = b where the matrix A and right-hand side vector b have entries A l,m = T j,m Φ(x l , x)ds(x) and b l = −g † (x l ), respectively.…”

“…[35,61,77]) and fractal piezoelectric ultrasound transducers (see e.g. [2,3,34,57]) (fractal structures being attractive in these contexts because of the possibility of wideband performance), and configurations that arise in the study of fractal aperture problems in laser physics [27,43,46,75]. The current study into acoustic scattering by fractal screens represents a first step towards the rigorous numerical analysis of integral equation methods for the study of such challenging problems involving fractal scatterers.…”

Ultrasound Systems for Biometric Recognition

“…With respect to classical piezoceramic materials, piezocomposites provide in general higher energy conversion efficiency and larger bandwidth. Despite of their well-established use, an intense research activity on this kind of transducer is still carried out [43,44,45].…”

Design, analysis and testing of monometallic plate stepped broadband high sensitivity transducer

“…This allows sonar systems to achieve long-range detection and detect weak signals while improving the communication speed, confidentiality, and reliability of sonar systems in signal transmission [2]. The current methods to expand the working bandwidth of hydroacoustic transducers are mainly the following: one is to change the material of the sensitive element in the transducer, take composite materials instead of piezoelectric ceramics, and increase the loss to reduce the mechanical quality factor, thus expanding the working bandwidth of the transducer [3][4][5][6]. However, this comes at the cost of reduced sensitivity and can also lead to problems such as thermal deformation of the piezoelectric composite.…”