A novel reduced-size rat-race coupler using stepped impedance structure

In this study, we propose a novel reduced-size rat-race coupler using stepped impedance structure with the bended and folded techniques. The bandwidth of this circuit is over 45%, and the size reduction is over 80%. The proposed method does not need any lumped elements, via hole grounding, and bonding wires, which lead to a low cost and simple fabrication process. It is very suitable for the MICs and MMICs applications.