Basic equations
Acoustic components used for filtering

Here we consider a generic stack of infinitely extended layers in the x₁ and x₃ directions. We use the axis conventions defined on 2. This is the coordinate system classically employed in surface wave models: the x₂ axis is oriented downwards so as not to have to deal with negative coordinates when considering the substrate. Since we are interested in monochromatic plane wave propagation, we assume that all fields possess a spectral harmonic dependence in exp(jω (t - s_<x_<)), with s_< the phase slowness along the corresponding axis and ω the pulsation, so that ω s_< represents the wave vector along x_<. We write the mechanical stress tensor T_ij and the electrical displacement...