A new ultra wideband directional coupler based on a combination between CB-CPW and microstrip technologies

In this paper, a novel ultra wideband directional coupler employing conductor backed coplanar waveguide CB-CPW and microstrip multilayer slot coupling technique is presented and implemented. The coupler uses two different transmission lines CB-CPW and microstrip, printed on two stacked substrate layers and coupled through a rectangular slot etched on a common ground plane located between these lines. Firstly, an analysis technique was used to obtain the coupler even and odd mode characteristic impedances. Secondly, using this approach, a new design of the directional coupler was performed. Simulation and experimental results show a good performance in terms of bandwidth, which covers the entire ultra-wideband operation (3.1–10.6 GHz).