### SAW Parameters Analysis and Equivalent Circuit of SAW Device [chapter]

Trang Hoang
2011 Acoustic Waves - From Microdevices to Helioseismology
Introduction 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
more » ... nce 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. Calculation of SAW parameters 2.1 SAW parameters The most important parameter for SAW device design is the center frequency, which is determined by the period of the IDT fingers and the acoustic velocity. The governing equation that determines the operation frequency is: www.intechopen.com Acoustic Waves -From Microdevices to Helioseismology