A novel design of high directivity CPW directional coupler design by using DGS

A GBSC CPW (General Broadside Coupled Coplanar Waveguide) directional coupler with DGS (Defected Ground Structure) is presented, which has an excellent directivity. An even-odd analysis is performed for the GBSC CPW directional coupler with DGS. Using the analysis method, a high directivity directional coupler, which has an arbitrary coupling coefficient is designed. As an example, a 3dB coupler is fabricated and measured at 2GHz. The measured directivity of the directional coupler is higher than 44dB.