Coplanar waveguide bend with radial compensation

A radial compensation was designed for suppressing the slot mode generated in a bend of a coplanar waveguide by an incident quasi-ThM mode. This compensation consists of a quarter-disk patch etched on the back side of the substrate. In an experiment, a coplanar bend was connected between two SMA connectors. With no compensation the slot mode would resonate at a frequency where the compensation was then made to cancel this resonance. An appropriate radius for the patch was obtained using a simple transmission-line model. An accuracy for the predicted centre frequency of better than 92% was observed