New interface design from substrate-integrated to regular coplanar waveguide

A new design for a substrate-integrated waveguide (SIW) interfacing a regular coplanar waveguide (CPW) is reported and compared to a transition employing conductor-backed CPWs and via holed side walls. The new interface provides, first, better return loss and, secondly, larger bandwidth as demonstrated by the related modes in a dispersion diagram. The interface is optimized in an HFSS environment for single and back-to-back transition. Both single and back-to-back designs achieve more than 24 dB return loss between 18.5 GHz and 27 GHz. Their improved performances, which include dielectric and all metallic losses, are demonstrated by direct comparison with a transition involving conductor-backed CPWs and via holed side walls. Verification by CST Microwave Studio validates the designs. All dimensional parameters are specified.