Evaluation of an Equivalent Circuit Model for Simulation of Surface Acoustic Wave Sensors

This paper presents a study of an equivalent circuit for surface acoustic wave (SAW) devices in the context of SPICE simulations, but valid for any other circuit simulation tool. We expand on previous derivations of the Foster Theorem approximation of impedances, providing normalized tables that evaluate LC pairs for different orders of approximation, also comparing their relative error. We propose a simple circuit block that can be used to represent external perturbations in a SAW delay line, while also including a parallel capacitance to model the electromagnetic coupling between input and output IDTs, an important effect when working with liquid media. Our results show close agreement with the measurements, along with interesting time-domain behavior not discussed by other works.