Electrostatics of interdigital transducers

Interdigital transducers are systems of conducting strips on a piezoelectric halfspace; in some systems, the groups of strips repeat periodically over a transducer counting hundreds of strips that can be considered infinite. An infinite planar periodic system of groups of strips with adequate period, sufficiently large if necessary, is considered to model an electric field in the plane of strips. There are electric charge distributions on strips either resulting from an external voltage source applied to the strips or induced by a propagating surface acoustic wave in the piezoelectric substrate. The latter case is equivalent, in the electrostatic approximation applied in this paper, to strips embedded in an already existing, spatially variable electric field. A method is presented for evaluation of the spatial spectrum of charge distribution that is responsible for either the surface wave generation or the scattering by strips in weak piezoelectrics. It overcomes certain numerical difficulties arising when Fourier transform is computed from the already evaluated numerical representation of the square-root singular charge distribution at the strip edges.