SAW Parameter Extraction Using Finite Element Analysis

Surface acoustic wave devices apart from being small, rugged and reliable can also be used as wirelessly interrogatable and completely passive devices in hostile environments. As complex signal processing functions can be performed with a simple structure through the variation of electrode patterns they can power wireless sensors and actuators in a secure manner. It is important to develop exact SAW parameter measurement techniques and simulation methods that are able to model the SAW devices accurately. Contrary to the frequently used FEM/BEM numerical simulation techniques, in this paper a versatile finite element modelling is employed to automatically include the second order effects in the device by considering the complete set of partial differential equations. The eigenmodes and the harmonic admittance of a periodic structure obtained from the FEM simulations are used to extract the COM/P-matrix parameters with the help of a fitting technique. The extracted parameters are compared to the ones in the literature for the same device specifications. Moreover, a SAW transducer is modeled for a specific device length from the extracted parameters.