Depolarization in nonuniform multilayered structures-full wave solutions

Abstract

In view of the recent impetus to produce rigorous solutions to more realistic models of pertinent propagation problems over a wide range of frequencies, we present in this paper full wave solutions to the problem of radio wave propagation in nonuniform multilayered structures. The electromagnetic properties of the media, the geometry of the irregular structure, and the electromagnetic source distributions are assumed to be arbitrary three-dimensional functions of position. Generalized field transforms are employed to provide a basis for the expansion of the transverse electromagnetic fields and Maxwell's equations are reduced to a set of first-order coupled differential equations for the forward and backward, vertically and horizontally polarized wave amplitudes. For open structures the complete wave spectrum includes the radiation term, the lateral waves, and the surface waves or trapped waveguide modes. For structures bounded by impedance walls (or perfect electric or magnetic walls μ/ε → 0 and ε/μ → 0, respectively) the fields are expressed exclusively in terms of waveguide modes. Exact boundary conditions are imposed at all the interfaces of the structure and the general solutions are not limited by the (approximate) surface impedance concept. The full wave approach employed is not restricted by frequency considerations. It is applicable to very broad classes of problems in which no single constituent of the total formal solution dominates. The full wave solutions may be applied to problems such as (i) propagation of ground waves over irregular and inhomogeneous terrain, (ii) scattering by rough surfaces and objects of finite dimensions, and (iii) propagation of guided waves in nonuniform artificial waveguides as well as in irregular ducts in the earth's crust or in the ionosphere.