Impact of Ground Via Placement and Size in Grounded Coplanar Waveguide Interconnects

The traditional coplanar waveguide (CPW) is a planar transmission line consisting of a central signal conductor flanked by semi-infinite grounding layers on both sides, enclosed within a dielectric substrate. To accommodate mixed coplanar and microstrip line circuits, an additional lower ground plane (LGP) is introduced, creating a conductor-backed CPW (CBCPW). The optimal structural parameters of finite side ground CB-CPWs (FG-CBCPWs) are determined. To suppress higher-order modes, vias are used to connect the coplanar side grounds (CSGs) to the LGP, resulting in grounded coplanar waveguides (GCPW). The paper investigates the impact of via placement and size on the GCPW bandwidth. To improve the GCPW bandwidth, a grounding via structure is introduced, and the parameters of the via fence that affect the bandwidth are discussed. The paper also analyzes the effects of varying via sizes to enhance GCPW performance while considering fabrication and routing requirements. Simulation results validate the effectiveness of the proposed method, demonstrating that the model meets the design requirements.