Conductor-backed slot line and coplanar waveguide: dangers and full-wave analyses

Despite the many attractive features of conductor-backed slotline and coplanar waveguide, there are potential problems that are introduced by the use of conductor backing. These potential problems include leakage of power into surface waves or into the dielectric region between the plates, unexpected crosstalk, significant alteration of the guide wavelength, and unexpected or unwanted coupling to neighboring lines. Two theoretical approaches are presented, one purely numerical and the other in network form and analytical in nature, that agree well with each other and with measurements in a special case. They provide a quantitative description of these potential surprises when the line conductors are either infinite or finite in width.<>