An efficient evaluation of the electrostatic fields in IDTs with periodic electrode sequences

Methods for the determination of the electrostatic fields for an IDT have long been a problem of great concern in SAW research. The approaches are either based upon field superposition or numerical methods. Due to its closed form analytic nature, superposition has become the most popular and has been used with great success. The need for numerical methods arises when describing transducers of finite length or with irregular electrodes. While more flexible,, numerical methods result in systems of equations where the number of unknowns can far exceed the number of individual electrodes. A new numeric method is presented which restricts the number of unknowns to be exactly equal to the number of electrodes being considered. The approach is based upon a modification of the work of Peach (1981). The method is described and applied to several different popular IDT structures. For each IDT type, the relative transduction coupling electrostatic capacitance, and elemental electrostatic field distributions are presented