Modelling, simulation, and design of SAW grating filters

A systematic procedure for modeling, simulating, and designing SAW (surface acoustic wave) grating filters taking into account losses is described. Grating structures and IDT (interdigital transducers) coupling to SAWs are defined by cascadable transmission matrix building blocks. Driving point and transfer characteristics (immittances) of complex architectures consisting of gratings, transducers, and coupling networks are obtained by chain-multiplying building-block matrices. The authors´ main focus is on an approach to resonator filter analysis and design which unifies and consolidates various valuable, yet frequently incompatible, published results. A multipole filter design procedure is given that is useful for filter designers and that is based on a lumped-element-model approximation of one-pole two-port resonator building rocks. The range of validity of this model is examined. The software for simulating the performance of SAW grating devices based on this matrix approach is described, and its usefulness, when linked to the design procedure to form a CAD/CAA (computer-aided design/computer-aided analysis) multipole filter design package, is illustrated with a resonator filter design example