Analytical optimization of piezoelectric acoustic power transfer systems

Acoustic power transfer and communication through metal layers is of great interest in many applications where the integrity of metal boxes, tanks, pipes or walls must be preserved by avoiding through-hole electrical connections. While acoustic power transfer has been widely studied last decades, the optimization of such systems has not been assessed comprehensively regarding the choice of transducers' dimensions and materials and the impact of the wall characteristic acoustic impedance. This paper stands at answering these optimization issues, using a new implementation of an analytical model and two figures of merit to evaluate performances: the power transfer efficiency and a new figure of merit, the normalized transmitted power, a crucial characteristic for electronics implementation. Among other results, we disprove the commonly used design rule stating that equalizing the characteristic acoustic impedance of wall and transducers is the best option. We propose a method to quantify the impact of acoustic impedance mismatches on performances and show that intermediary layers sized with our optimization process can solve these acoustic impedance issues, resulting in an important gain in the transmitted power (multiplied by 40 in our example) and opening up great opportunities for the acoustic power transfer technology.