Two dimensional periodic array of reflection centers on electrodes in SAW resonators

Abstract

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(ηt) and the period( ‫۾‬ ‫ۺ‬ ) 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 the frequency band for = ቂ, ቃ. By evaluation of the overlap integral of the excitation and mode profile, and consequently, the analysis of the single mode contribution to the excitation strength, it is demonstrated that higher modes are responsible for remaining spurious peaks in the resonator's frequency response. The analysis of the contribution of the transversal modes to the admittance provides insight how the ∆/ waveguide, formed by the areas with and without patches, can be engineered to suppress bound and leaky continuum modes.

Advanced 2D periodic array and full transversal mode suppression

“…Similar to the energy level in a quantum well, we calculate the velocity of the first symmetric mode in a single velocity well with respect to the effective velocity (v m = λ • f m ), where f m is the n th mode frequency and can be computed using a parabolic approximation of the slowness curve [1]. In reality, the number of PVWs is finite so that the perturbation of the first mode velocity increases toward the end of the PVWs.…”

“…When such resonators are used in filter designs without taking any countermeasures, the transversal modes lead to unacceptable passband ripples [2], [3]. In the previous work [1], we have demonstrated that a 2D periodic array with patches on electrodes can successfully get rid of undesired modes within the frequency band of k y = 0, π p T , where p T is the transversal pitch of the periodic array. However, the resonator exhibits strong conductance at frequencies, where the wavelength of the y-components of the transversal modes is comparable to transversal pitch of the patches.…”

“…In this work, we have conducted further investigation on 2D periodic arrays from [1] in order to minimize the transversal resonance while fully suppressing all unwanted transversal modes. At the initial step, simulations were performed utilizing the well established 2D P-matrix model.…”