A Perturbation Method for the Analysis of Eccentric Coaxial Waveguides

This paper describes a novel analytical solution for the modal analysis of eccentric coaxial waveguides based on a perturbation method. Different techniques have been used for solving this kind of problem, and the majority of then rely on solving a complicated transcendental equation obtained from the Graf's addition theorem, or on numerical methods such as the finite-element method (FEM). In our approach, instead, a transformation optics is employed to turn the original problem into a concentric coaxial waveguide filled with anisotropic and in-homogeneous medium. A corresponding (transformed) Helmholtz equation is then solved via a perturbative approach that allows us to obtain field solutions in terms of a set of orthogonal transverse electric (TE) and transverse magnetic (TM) modes. We present validation results which show that our technique can accurately model eccentric coaxial waveguides providing cutoff wavenumbers and field pattern in a computationally efficient manner.