Devices that employ surface acoustic waves in the analog processing of electronic signals in the frequency range 10⁷–10⁹ Hz. Surface acoustic waves are mechanical vibrations that propagate along the surfaces of solids. In 1885, Lord Rayleigh discovered a type of surface acoustic wave that contains both compressional and transverse components 90° out of phase with one another. Since that time, other types of surface acoustic waves have been discovered and are an active area of intense research. A few notable examples include a wave propagating along a layer on a surface (Love wave), a wave propagating along an interface between two solids (Stoneley wave), and transverse guided waves on solids (Bleustein-Gulyaev-Shimizu waves). Love waves are shear-horizontal (SH) waves that have displacement only in a direction perpendicular to the plane of propagation.