Analysis of shielded ring waveguide

The shielded ring waveguide is composed of a periodic array of closely arranged rings enclosed in a coaxial perfectly conducting pipe. The ring is a perfectly conducting tape ring with infinitesimal thickness. The propagation properties of this waveguide have been investigated theoretically. The circularly symmetric modes are considered. The electromagnetic fields are expanded into a Fourier series according to Floquet's theorem and the boundary conditions are imposed to obtain dual series equations. The method of Riemann-Hilbert problem is applied to them for analytical regularization. Putting the determinant of the resulting matrix into zero yields the dispersion equation. The dispersion curve of the circular magnetic mode is given as well as that of the circular electric mode. The numerical results show that the circular electric modes are considerably influenced by the ring array but that the circular magnetic modes are lightly affected by it.