Modelling of SAW filter based on ZnO/diamond/Si layered structure including velocity dispersion

A simulator based on the coupling of mode (COM) theory, previously developed for modelling the bulk substrate surface acoustic wave (SAW) devices, was modified to be adapted for layered structures. The frequency response of ZnO/diamond/Si-SAW filter was calculated and the results were compared with experimental ones extracted from the literature. A good agreement is obtained for the frequencies within and close to the pass-band of the filter. Outside of this pass-band, the experimental frequency response exhibits an asymmetry, which is not reproduced by the simulation. This asymmetry is attributed to the dispersion, as a function of frequency, of SAW velocity (V-P) and electromechanical coupling coefficient (K-2), which cannot be neglected in the case of layered structures. In the original program developed for bulk structures, K-2 and V were assumed to be constant. To take into account the effect of dispersion, the program was modified by the introduction of a dispersive model. The confrontation between the results obtained by simulation, including the dispersive model, and by experimental measurements shows a good agreement. (C) 2000 Elsevier Science B.V. All rights reserved.