A microwave network formalism for acoustic waves in isotropic media

Abstract

Motivated by recent developments in acoustic surface waves, a new approach is presented for the systematic analysis and description of acoustic wave phenomena in isotropic solids. This approach employs certain microwave network techniques developed in the context of electromagnetic waveguides. Acoustic wave structures are viewed as being composed of constituent waveguide regions coupled by junctions or ending in terminations; the waveguide regions are described in terms of equivalent transmission lines and the junctions or terminations by lumped equivalent networks. These transmission lines and equivalent networks contain electrical symbols and are cast into pictorial forms familiar in electrical engineering, but they represent purely acoustical quantities and effects. A rigorous transmission-line formalism is presented for acoustic wave propagation in uniform isotropic regions, which takes account of the translational invariance, reflection symmetry, and power orthogonality of the modal fields. This formalism is much more than a rephrasing of acoustic wave phenomena in terms appealing to electrical engineers; it forms the basis for a rigorous and practical procedure for solving complicated acoustic wave problems, and it yields pictorial insight into wave interactions. Despite its recent development, the method has already been applied successfully to several problems of current interest.