Attenuation in Lossy Circular Waveguides

We present a simple closed-form approach to calculate the attenuation of waves in lossy circular waveguides. A set of characteristic equations is first derived by matching the tangential fields at the wall boundary with the constitutive properties of the conducting wall material. In order to represent fields’ penetration into the lossy wall, a perturbation term is then introduced into the equation. We apply the Finite Difference Method to derive the closed-form expression of the perturbation terms for TE and TM modes. The propagation constant can be found by incorporating the perturbation term into the dispersion relation. Our results show good agreement with those obtained from the rigorous transcendental equations. However, unlike the transcendental approach which is usually laborious in solving, our closed-form approach leads to simpler analysis and, therefore, allows the attenuation to be easily computed.