An extended Huygens' principle for modelling scattering from general discontinuities within hollow waveguides

The modal "elds, generalized scattering matrix (GSM) theory and dyadic Green's functions relating to a general uniform hollow waveguide are brie#y reviewed in a mutually consistent normalization. By means of an analysis linking these three concepts, an extended version of the mathematical expression of Huygens' principle is derived, applying to scattering from an arbitrary object within a hollow waveguide. The integral-equation result expresses the total "eld in terms of the incident waveguide modal "elds, the dyadic Green's functions and the tangential electromagnetic "eld on the surface of the object. It is shown how the extended principle may be applied in turn to perfect conductor, uniform material and inhomogeneous material objects using a quasi method of moments (MM) approach, coupled in the last case with the "nite element method. The work reported, which indicates how the GSM of the object may be recovered, is entirely theoretical but displays a close similarity with establishedMM procedures. Copyright 2001 John Wiley & Sons, Ltd.