A Finite Difference, First-Order Perturbation Method for Attenuation in Arbitrarily Shaped Waveguides

The simplest and most frequently used method employed in the calculation of waveguide wall losses proceeds as follows: (1) solve the electromagnetic field under the assumption that the walls are perfectly conducting; (2) calculate the wall currents through knowledge of the magnetic field tangential to the wall; (3) square the current, at each point on the conductor surface, and multiply by the equivalent resistance due to skin effect R _s = √ ωμ _o / 2σ; and (4) integrate over the entire surface to obtain the total power loss. Note that the initial assumption of perfectly conducting walls excludes six-component hybrid fields from consideration --- which, in fact, must exist.