Mode profile shaping with 2D periodic array of metallic patches on electrodes in SAW resonators

Periodic arrays of metallic patches on the electrodes of a Rayleigh-type SAW resonator are investigated to suppress undesired modes above resonance frequency. Both, the metallization ratio(η_t) and the period(p_T) of the patches in transversal direction, were varied. Simulations were performed employing the well established 2D P-matrix model. A well-designed periodic array is capable to suppress all transversal modes within a certain frequency band. The individual transversal modes are well characterized by evaluating the overlap integral of the transversal excitation and mode profile as well as the field strength. From these evaluations it is also possible to understand the mechanism of mode suppression. It has been demonstrated that the modification of the higher symmetric modes caused by patches is responsible for strong spurious peaks in the resonator´s frequency response. These results provide insight how the Δv/v waveguide, formed by the areas with and without patches, can be engineered to suppress bound and leaky continuum modes.