Dispersion Analysis of Sectoral Corrugated Waveguides Using Subdomain and Block-Circulant Matrix Formulation

This study presents the subdomain method with local coordinates and the mode-matching method to compute the dispersion relations of sectoral corrugated waveguides. Fields are expanded in local Fourier–Bessel series, and boundary conditions are enforced by mode-matching, which produces a block-circulant system matrix. The method reduces computational cost while preserving accuracy, as verified by numerical results.