Rayleigh waves and leaky SAW in periodic systems of electrodes: Periodic Green´s function analysis

A new method of calculating the dispersion curves and attenuation coefficients for Rayleigh waves propagating in a periodic system of thin electrodes on a piezeoelectric surface is proposed. This method uses periodic Green´s functions with a propagation factor exp(iβχ) that is not known in advance. To describe the charge distribution on the electrodes, both a step approximation and Chebyshev polynomials are used, the latter being more adequate in most cases. Numerically determined values of the Green´s function are used and interpolated either linearly or using a modified variant of Ingebrigtsen´s formula. Such basic parameters as stopband width, stopband center frequency, wave velocity, and attenuation in the stopband are found. These parameters can be used in a coupling-of-modes (COM) analysis for the design of surface acoustic wave (SAW) devices. The analysis includes the bulk wave radiation and scattering. The corresponding attenuation coefficient dependence on frequency is determined. Numerical results for Rayleigh waves on YZ-LiNbO ₃ and leaky waves on 36° YX-LiTaO₃ substrates are presented