New features of wave propagation not subject to cutoff between two parallel guiding surfaces

Wave propagation not subject to cutoff between two parallel guiding surfaces is generally described in terms of the so-called TEM mode. Although this is recognised to be an over simplification, it is nevertheless very close to the truth in many cases when bare copper conductors are used to form the guiding surfaces. However, at high frequencies, such surfaces, having very nearly equal resistive and reactive components which are not entirely insignificant, tend to require the support of a hybrid TEM-dual-surface-wave mode, and this can be readily accentuated by deliberately enhancing the surface reactances. Investigation shows that the accompanying redistribution of power flow over the cross-section of the guide can, in appropriate circumstances, lead to a very significant reduction of the attenuation suffered by the wave. The technique is applicable both to striplines and to coaxial cables.