Crosstalk reduction in a piezoelectric phononic plate induced by electrical boundary conditions: Application to...

This paper proposes a method of passive electrical decoupling which aimed at found application in reducing the crosstalk phenomenon in multi-element ultrasonic transducers. A homogeneous piezoelectric plate, covered on one side by a 1D periodic arrangement of thin metallic electrodes and on the other side by a full electrode, is considered. Finite element analysis and experimental measurements are performed to obtain the dispersion curves and normal displacements at the surface of the structure. It is shown that applying inductive shunts at the electrodes, band gaps can be created in the first Brillouin zone, which can prevent from the establishment of the first thickness mode in the plate. In that way the mechanical inter-element coupling can be lowered. Thus, the acoustic radiation in water from one sector excited at the resonance frequency is found to be closer to that of a piston mode. The transposition of this principle to the situation of a transducer including a rear medium and a front matching layer confirms the possibility of reducing the inter-element coupling. However, the physical effects at the origin of this reduction are different from those inherent to the cutting of a piezocomposite ceramic as it is done in most probes available in the market. As a result, we show that taking advantage of the electrical boundary conditions upon the passive elements in a transducer gives real opportunities for crosstalk reduction that may be implemented in ultrasonic systems for imaging in the medical field and in NDT.