Eigenmodes and scattering by an axial array of tape rings

Source-free and forced solutions for the electromagnetic fields in and around a periodic array of finite-length conducting cylinders are assembled from a Galerkin procedure using a Chebyshev polynomial basis with built-in edge-condition behavior. A localized source excites slow surface-waves under certain conditions on the electrical circumference and spacing of the tubular structure. These eigenmodes are the solutions to the homogeneous boundary value problem. A numerical search for the axial propagation constant that minimizes the smallest singular value of the governing Galerkin matrix provides the required dispersion relation.