Dual band/ Dual Mode Branch-Line/Rat-Race Coupler Using Artificial Transmission Line

This paper presents a novel dual band/dual mode compact hybrid coupler which acts as dual-functional, a dual band branch line coupler at lower band but a rat-race coupler at higher band. The outputs of the proposed coupler at the each mode of operation are the same side. This unique design is implemented by using artificial transmission lines (TLs) based on open split ring resonators (OSRR). The proposed low cost miniaturized coupler could be operated as a dual band 90° branch line coupler at 3.3 and 3.85 GHz and 180° rat-race coupler at 5.3 GHz.