SAW Parameters Analysis and Equivalent Circuit of SAW Device

Abstract

Surface Acoustic Wave (SAW) devices, using interdigital electrodes, play a key role in today’s telecommunication systems and are widely used as electronic filters, resonators, delay lines, convolvers or wireless identification systems (ID tags). During the last three decades, demands set by the expansion of the telecommunication industry and many applications in sensor have resulted in the introduction of a new generation of the SAW devices. Consequently, the design of high performance SAW devices requires precise and efficient models, simulation tools. Several methods have been proposed for modeling, analyzing SAW devices. These include the impulse model, the equivalent circuit models, the coupling-of-mode (COM) model, P-matrix model, angular spectrum of waves models [1] and the Scattering Matrix approach that was presented by Coldren and Rosenberg [2]. While the impulse model is only a first order model, the other models include second order effects, e.g. reflections, dispersion, and charge distribution effects. Purely numerical methods have also been and are being developed by many authors [3][35], [41]. In this chapter, the method for calculating the SAW parameters, including modeling and simulation, is given. Section 2 gives the calculation of SAW properties and analyses of different SAW device structures. Section 3 presents the equivalent circuit of SAW delay line based on Mason model. The equivalent circuit of SAW delay line based on Couple-Of-Mode theory is presented in section 4. Based on section 3 and 4, section 5 shows comparison between using the equivalent circuit of SAW delay line device based on Mason model and COM theory. This model is useful and fast model for designing the SAW device.