Theory and experiments of simultaneous propagation of both bound and leaky dominant modes on conductor-backed coplanar strips

Contrary to expectations, we found recently that a new leaky dominant mode may be present on conductor-backed coplanar strips at the same time as the conventional bound dominant mode. The frequency range over which both these modes can propagate simultaneously increases as the strips become wider, and can be quite large even for fairly narrow strips. These new features, which could affect circuit performance significantly, have been derived theoretically and verified by measurements.