Coupled Slotline Mode Suppression for Bent Coplanar Waveguide Using Double-Ended Open-Circuited Stubs

This article applies the double-ended open-circuited stubs to suppress the coupled slotline (CSL) mode in the bent coplanar waveguide. Three structures are investigated: the shorter slotline compensation structure; the CSL mode filter structure; and the hybrid structure. The shorter slotline compensation structure places the double-ended open-circuited stubs underneath the shorter slotline of the coplanar waveguide to compensate for the phase difference between the shorter and longer slotlines of the coplanar waveguide. The resulting CSL mode conversion is as small as −15 dB from dc to 12.5 GHz. The CSL mode filter structure places the double-ended open-circuited stubs underneath both the shorter and longer slotlines of the coplanar waveguide to generate a resonant frequency for the CSL mode of the coplanar waveguide at 12.5 GHz. The resulting CSL mode conversion is as small as −15 dB from 12.5 GHz to 20 GHz. By integrating the shorter slotline compensation structure and the CSL mode filter structure, the hybrid structure's resulting CSL mode conversion can be as small as −20 dB from dc to 20 GHz. Furthermore, the signal integrity of the coplanar waveguide mode is improved.