Electromagnetic propagating structures with nonuniform gross perturbations

Abstract

The perturbation technique presented in a companion paper is here extended to permit even gross perturbations. A generalization and modification of the Brillouin-Wigner method, the present iterative procedure circumvents expansions in powers of a perturbation parameter, but retains a normal mode expansion. Much improvement in convergence is obtained over the previous technique, an adaptation of the usual Rayleigh-Schroedinger perturbation expansion, which converges only for small perturbations. Following a demonstration of improved convergence, through an example whose exact solution is known, the generalized method is applied to problems involving time-harmonic electromagnetic radiation from axial arrays of parasitic elements perturbing an open traveling-wave structure. Both the element pattern and the space factor, corrected to include the change in phase progression of the exciting traveling wave in the presence of the parasites, are automatically included in the expressions for the radiated power. Mutual coupling, or multiple scattering, and polarization effects due to the vector character of the electromagnetic fields are also included in the formalism.