No 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.

No abstract

No abstract

Abstract-The resonance frequency of an active element in a piezoelectric ultrasonic transducer is dependent on its length scale. Inspired by natural occurring auditory systems, incorporation of elements with varying length scales in the piezoelectric transducer design can result in a wider operational bandwidth. In this paper, a mathematical algorithm was developed first to define the feature of a fractal geometry called the Cantor Set (CS), then a series of parameter sweep simulations are performed to design a CS fractal array transducer and a conventional array transducer and optimize their performance. The behaviors of these two array transducers were explored theoretically, using finite element modeling and experimentally using the scanning laser vibrometry. The FE simulation results and experimental results correlate well with each other, which indicates an approximate 30% operating bandwidth enhancement and a 5 dB side lobe reduction can be achieved by the CS fractal array compared to the conventional linear array design.