Efficient modal analysis of bianisotropic waveguides by the coupled mode method

A modal analysis based on the coupled mode method is performed for the resolution of partially filled waveguides with a general bianisotropic medium. The calculation of the generalized telegraphist's equations can be made by using two different strategies: direct and indirect formulations. In this paper, the indirect formulation of the method is extended to bianisotropic materials and exposed in detail. The convergence of both formulations is compared and it is demonstrated that the indirect formulation converges much faster than the direct formulation, which means that fewer modes are required for a given precision. Results of some particular cases of the constitutive relationships, like dielectric, magnetic, ferrites, and omega materials are shown and compared with the bibliography or commercial electromagnetic simulators. Good agreement is found, which demonstrates the validity and reliability of the method.