Acoustic wave parameter extraction with application to delay line modelling using finite element analysis

In this paper we propose a practical approach to develop a SAW parameter extraction technique and simulation method, contrary to the frequently used FEM/BEM numerical simulation technique. The new approach allows for accurate SAW device modelling through a versatile finite element method to automatically include the second order effects in the device by considering the complete set of partial differential equations. The eigenmodes and the harmonic admittance of a periodic structure obtained from the FEM simulations are used to extract the COM/P-matrix parameters based on a fitting technique that is already published in the literature. Comparison between the extracted parameters, using this technique, with currently published parameters for the same device specification was carried out and showed good agreement. As an example, a two dimensional delay line with 10 finger pairs per IDT was modelled using this approach, to outline the mechanical and electrical response of the device for variable acoustic modes and substrate thicknesses.Ajay Tikka, Said Al-Sarawi and Derek Abbot