A Reduced Three Dimensional Model for SAW Sensors Using Finite Element Analysis

A major problem that often arises in modeling Micro Electro Mechanical Systems (MEMS) such as Surface Acoustic Wave (SAW) sensors using Finite Element Analysis (FEA) is the extensive computational capacity required. In this study a new approach is adopted to significantly reduce the computational capacity needed for analyzing the response of a SAW sensor using the finite element (FE) method. The approach is based on the plane wave solution where the properties of the wave vary in two dimensions and are uniform along the thickness of the device. The plane wave solution therefore allows the thickness of the SAW device model to be minimized; the model is referred to as a Reduced 3D Model (R3D). Various configurations of this novel R3D model are developed and compared with theoretical and experimental frequency data and the results show very good agreement. In addition, two-dimensional (2D) models with similar configurations to the R3D are developed for comparison since the 2D approach is widely adopted in the literature as a computationally inexpensive approach to model SAW sensors using the FE method. Results illustrate that the R3D model is capable of capturing the SAW response more accurately than the 2D model; this is demonstrated by comparison of centre frequency and insertion loss values. These results are very encouraging and indicate that the R3D model is capable of capturing the MEMS-based SAW sensor response without being computationally expensive

Attenuation of Lamb Modes and SH Waves near cut-off Frequencies

Near cut-off frequencies, the shear horizontal (SH) and Lamb modes in a platelet are created by a bulk acoustic wave bouncing up and down between the platelet sides in an almost vertical direction. The small inclination angle corresponds to slow drift of energy along the platelet (low group velocity), but the attenuation of the bulk wave accumulates fast. Therefore, the attenuation of these waves along the platelet near the cut-off frequency is high, being roughly inversely proportional to the group velocity

COMSOL modeling of SAW Resonators

Here we demonstrate some generic 2D and 3D routines for SAW analysis employing the commercial COMSOL Multiphysics platform for finite element analysis (FEA). More specifically, we consider the analysis and optimization of high performance LSAW resonators for RF filters. The LSAW nature - being well studied and sufficiently complicated - is chosen as a suitable example for analysis and the results are compared to state-of-the-art knowledge. We found very good agreement between the results of the analytical scheme proposed here and the state-of-art findings. Finally, we demonstrate a TC-SAW piston-mode device simulated using SiO2/128 degrees Y-X LiNbO3

Bulk Acoustic Wave Transformer employing Periodically Polled array of Piezoelectric Rods

Multilayer bulk acoustic wave transformer employing a periodical array of piezoelectric rods with alternating polarization is experimentally demonstrated for the first time. Voltage transformation coefficient in excess of 6 was measured at a frequency of 150kHz, providing thus a solid experimental verification of the recently proposed principle of operation. Finite element analysis is used to reveal the underlying device physics