FEM -Based Estimation of SAW Power Flow Angle in Periodic Gratings

This paper proposes a technique to estimate surface acoustic wave (SAW) power flow angle (PFA) in periodic grating structures. First, the thin plate model is extended to take into account non-zero PFA. The relation between the lateral wavenumber and the frequency is derived in an analytical form under the longitudinal resonance condition. Then, the complex power flows in lateral and longitudinal directions are derived and PFA is estimated from the model parameters. Finally, the parameters are extracted by fitting the derived relation between lateral wavenumber and frequency with that calculated by finite element method. The influence of grating electrode on PFA is investigated on quartz and langasite substrates. The results confirm the validity of the technique.