Design and Simulation of Surface Acoustic Wave Resonators using Multiple Models

Abstract

The development of the modern mobile telecommunication system standards has posed new performance requirements for all devices in this domain. The increase in the amount of data transmission means that more filtering components with higher operation fre- quencies in a single device is required. In this context, surface acoustic wave (SAW) and bulk acoustic wave (BAW) technology are preferred owing to their compact size and prominent operation at high frequencies. The thesis aims at the design and simulation process of SAW resonators which is important to optimize the device’s operation for today applications.

Four modelling approaches are used to analyze SAWs and different SAW resonator struc- tures: coupling-of-modes (COM), P-matrix, Butterworth Van-Dyke (BVD) equivalent circuit and finite-element-method (FEM). The formalism of these models and their step- by-step simulation procedure are presented, resulting in the analysis of different SAW behaviors. Furthermore, the methods to extract parameters are performed with matching results among the used models.

Two multilayered SAW resonator structures are analyzed. The structure with an overcoat SiO2 layer on a 128YX-LiNbO3 substrate is dedicated for temperature compensation. The suppression of spurious modes can be achieved when the overcoat thickness ratio is 0.2. The second structure with a sapphire substrate and 42YX-LiNbO3 piezoelectric layer is studied to acquire a higher wave velocity, enhance Q factor and electromechanical coefficient. As a result, when the thickness ratio ht of the piezoelectric layer is optimized from 0.1 − 0.25, better Q value and coupling coefficient of the main resonance can be achieved with little effect of the spurious mode exhibited.

Keywords: SAWs; design and simulation methods; FEM model; BVD equivalent circuit; COM model; P-matrix; SAW multilayered structures