Analysis of a SAW-BAW mutual transducer of finite length on piezoelectric substrates

This paper outlines the modeling of strong reciprocal couplings occurring on periodically corrugated piezoelectric substrates between SAWS (or STWs) propagating in their second stop band, i.e. with a wavelength close to the period of corrugations, and BAWs propagating either into or from the depth of substrate. The solution is classically expanded as series of Bloch functions allowing to obey periodic boundary conditions on the external surface. Those boundary conditions are actually taken into account by a simple integral method accessing the Fourier coefficients of the periodic part of effective stresses and induction on the free boundary of substrate. Treatment of piezoelectric effect is detailed together with issues regarding the effect of anisotropy, and results obtained on structures containing a finite number of gratings are briefly explained. The influence of the number of grooves on the energy conversion ratios is described.