Suppression of Unwanted Harmonics in Piezoelectric Transducers Using Phononic Crystals: Modeling and Simulation

Piezoelectric resonators are fundamental components in ultrasonic transducers, playing a crucial role in determining the overall performance of these devices across a wide range of applications, including medical imaging, therapeutic physiotherapy, and underwater sensing. The mechanical vibration modes of piezoelectric resonators at their resonant frequencies are particularly significant, as they directly influence the efficiency, sensitivity, and signal clarity of ultrasonic transducers. The resonator's geometry such as its thickness, diameter, shape and its dimensional parameters govern the oscillatory behavior at specific frequencies. This behavior arises mainly from the coupling and interaction of various contour vibration modes, including thickness, radial, and shear modes. However, unwanted vibrational modes, especially shear and radial modes, can interfere with the desired piston-like vibration, reducing the transducer's acoustic efficiency and degrading signal quality. To address these challenges, phononic crystals have emerged as a promising solution. Phononic crystals are artificially engineered periodic structures designed to manipulate elastic wave propagation through mechanisms like scattering and interference. In this study, a phononic crystal structure is developed by creating a periodic array of circular holes arranged in a triangular lattice along the resonant polarization axis of the piezoelectric resonator. This modification of the resonator's internal structure effectively alters wave propagation, resulting in a piston-like vibration pattern that suppresses undesirable shear modes while enhancing vibrations in the thickness direction. This selective mode filtering significantly expands the mechanical vibration domain, and improves the acoustic output of the transducer. The proposed model has been developed using Finite Element Method (FEM) simulations, which validate that the phononic crystal structure promotes efficient piston-like wave propagation while significantly minimizing unwanted harmonic distortions. These results suggest that fabricating an experimental prototype based on this design could play a crucial role in advancing high-performance piezoelectric transducers for therapeutic physiotherapy, where precise and controlled ultrasonic wave emission is essential for effective treatment.

کلیدواژه ها:

phononic crystals ، piezoelectric transducers ، physiotherapy ، FEM