Studies of Guided Electromagnetic Waves in the Presence of Axially Nonuniform or Random Perturbations

摘要

A perturbation technique to deal with gross nonuniformities in an otherwise axially uniform waveguiding structure is presented and applied to time-harmonic electromagnetic propagation in the presence of not necessarily small perturbations which may have both axial and transverse dependence and may be either deterministic or random. The method, an iterative procedure similar to the Brillouin-Wigner approach for uniform perturbations, circumvents expansions in powers of a perturbation parameter, which is one cause of poor convergence for perturbations not sufficiently small. As in standard analyses, an expansion in normal modes is utilized, but with the inclusion of a nonlinear phase progression term. Several deterministic examples, chosen to indicate the flexibility of the perturbation analysis to cope with a wide class of electromagnetic problems, are presented. Following a demonstration of the convergence, through an example whose exact solution is known, the method is applied to problems involving radiation from axial arrays of parasitic elements perturbing an open traveling wave structure. The technique is next applied to long distance very low frequency propagation in an idealized 'earth-ionosphere waveguide'. The analysis is finally applied to propagation in waveguides containing media with statistically inhomogeneous, random, gross inhomogeneities over a finite axial range. (Author)