Scattering at a Junction of Two Waveguides with Different Surface Impedances (Comments)

In the above paper, a criterion has been given in order to establish if the scattering problem of the junction between two waveguides with different surface impedances can be solved in closed form. In this comment, a different approach, based on a spectral formulation, shows that the possibility to obtain analytical expressions of the scattering coefficients depends on the form of the relevant Wiener-Hopf equation.