Rigorous analysis of STWs in nonperiodic arrays including mechanical and electrical interactions

The authors present a method for the analysis of surface transverse wave (STW) interaction with a finite number of arbitrary rectangular-shaped metallic electrodes (fingers), elastic ridges, and grooves. The metallic fingers having ideal conductivity and isotropic elastic properties are deposited on the surface of an anisotropic piezoelectric substrate supporting a shear horizontal wave. Arbitrary height, width, spacing, and electric polarity of the fingers can be assumed. Based on first principles, a model for the metallic fingers has been developed. In the finger regions the mechanical displacement is decomposed into a finite number of properly chosen eigenmodes, such that on the three free sides of each finger the stress vanishes. The remaining four mechanical and electrical boundary conditions in the substrate interface plane, in conjunction with Sommerfeld´s radiation principle in the substrate, complete the set of boundary conditions. A Fourier method combined with the method of weighted residuals has been applied to determine simultaneously the amplitudes of various modes in the fingers and the electrical charge density distribution on the finger surfaces