Enhanced dominant mode operation of shielded multilayer coplanar waveguide

The effects of substrate height and dielectric constant on the propagation characteristics of a multilayer shielded symmetrical coplanar waveguide (CPW) are examined using a full-wave spectral-domain analysis (SDA). It was found that the effective dielectric constant of the shielded CPWs displayed a cutoff frequency for the even mode which can be controlled by varying the height and dielectric constant of the substrate, especially those directly below the coplanar slots. The highest cutoff frequencies found in three-layer CPW configurations utilized air as the lower substrate dielectric. In certain multilayer CPW combinations, when the lower substrate was not air, a bandwidth maximization effect was demonstrated using internal substrates.<>