Attenuation in waveguide

It is demonstrated that strong absorption of a TM wave upon grazing incidence on a metal surface is analogous to total transmission of a TM wave incident on a dielectric surface at the Brewster angle. Vanishing reflectance of the metal surface leads to increasing attenuation of oscillations propagating in a waveguide. The ratio κ/k of the transverse wave number κ to the limiting wave number k is on the order of the surface impedance ζ. The attenuation coefficient of H and E waves in a circular waveguide is calculated for an arbitrary relation between κ/k and ζ. It is demonstrated that for κ/k≪ζ, the attenuation coefficient is less than that predicted by the theory based on successive approximations (see, for example, §90 in [1]).