Quasi-static analysis of floating-electrode unidirectional SAW transducers

The quasi-static theory of SAW transducers is a simplified Green's function analysis that has previously been shown to be effective for transducers in which short-circuit reflections are negligible. Here, the theory is extend ed to allow for floating electrodes, which occur in floating-electrode unid irectional transducers (FEUDTs). An analysis for the coupled-mode (COM) par ameters of FEUDTs is developed, giving the capacitance, transduction, and r eflection parameters and the locations of the transduction and reflection c enters. For a FEUDT with six electrodes per period, algebraic results are o btained in terms of Legendre function expressions, giving the COM parameter s as functions of metalization ratio. These results agree with earlier deri vations by other authors, but they are obtained much more simply. Numerical results are straightforward to obtain. A FEUDT with five electrodes per pe riod is also analyzed, showing that it performs similarly to the six-electr ode type.