An efficient method for determining TE and TM modes in closed waveguides made up of N cylindrical conductors

An efficient method for calculating TE and TM modes in closed waveguides made up of cylindrical perfect electric multiconductors and homogeneous isotropic media is presented. An ad hoc analytical formulation of the problem is carried out, and special emphasis is placed on its resolution. As a result, the determination of the cutoff wavenumbers is achieved using a robust and efficient algorithm. An adaptive approximation scheme is also proposed to ensure an acceptable precision and an efficient computation without missing any mode. Finally, several comparisons demonstrate the accuracy of the proposed method.