FEM/BEM analysis of infinite periodic grating covered with an SiO2 overlay

In order to improve the temperature stability of RF SAW devices, it is worth adding a layer of SiO₂ on the surface of the piezoelectric substrate. This paper presents an original method, which allows the computation of the Harmonic Admittance of an infinite periodic grating covered with an SiO₂ overlay. The origins of this method can be found in a previous paper. By comparison with S. Ballandras and K. Hashimoto works, this methods allows to take into account the very efficient Chebyshev-like charge distribution, together with a classical FEM basis interpolation for the stresses. FEM is used to model mechanical behavior of complex shape electrodes and BEM using a periodic Green´s function Kernel is used to take into account the semi-infinite piezoelectric substrate. Validations are presented by comparison with K. Hashimoto´s software.