Fullwave Analysis of Open-End Discontinuties in Coplanar Stripline and Finite Ground Plane Coplanar Waveguide in Open Environments using a Deterministic Spectral Domain Approach

Open-end discontinuities in coplanar stripline (CPS) and finite ground plane coplanar waveguide (CPW) are analyzed for the first time using a deterministic spectral domain method. The analysis includes the effects of radiation into space waves and dielectric slab waveguide modes. Unlike microstrip or coplanar waveguide with infinite ground planes, finite ground-plane CPW has two parasitic dielectric slab waveguide modes which have zero cutoff frequency. This strongly affects the losses at the discontinuities. Numerical results are presented for the reflection coefficients of representative CPW and CPS open-end discontinuities on high-dielectric-coefficient substrates which clearly show the effects of these losses. Also, numerical results are presented for an infinite ground plane coplanar waveguide short for comparison.