Rectangular and Annular Modal Analyses of Multimode Waveguide Bends

Spurious modes in multimode H-plane waveguide bends of nonuniform curvature are computed on the basis of rectangular and annular waveguide modal analyses. The sets of coupled differential equations for the wave amplitudes are solved numerically using both an iterative approach and the Runge-Kutta method. The advantages and limitations of the different approaches to this problem are considered in detail.