Effects of the bottom ground plate on coplanar waveguide structures

In this article, the authors study the significant practical effects caused by the presence of a conductor plate beneath a coplanar waveguide (CPW) structure. Specifically the authors pay attention to the effects on the dispersion characteristics of the bound modes and on the signal integrity. This study allows one to discuss the reported proposal on the use of this additional conductor plate as an inexpensive alternative to air-bridges in order to alleviate the possible spurious effects produced by the potential existence of asymmetries in CPW-based circuits.