Practical issues related to the design of UWB directional couplers in stripline technology

Recently, the study of slot-coupled directional couplers has led to compact and elegant topologies for UWB applications. The most common design consists in two elliptically shaped lines coupled through an elliptically shaped slot in a common ground plane. In this paper, this concept is applied to the design of Ku-Band directional couplers manufactured in stripline technology. It turns out that parallel plate waveguide modes (PPWM) are strongly excited, which impacts the overall working of the structure. In order to mitigate this issue, two solutions have been simulated and their results are compared.