Multilayer compact dual-band branch-line coupler using coupled line and open-ended stub for mobile phone application : (Invited Paper)

摘要

A compact dual-band branch-line coupler for the application of mobile phones has been proposed using multilayer PCB technology. The coupler contains six miniaturization units and two extra transmission lines (TLs). The miniaturization unit is introduced to replace the $lambda /4$ TL for size reducing. For further miniaturization, the overall structure of the coupler uses multi-Iayer technique. The proposed coupler has high isolation and flexible frequency ratio. A coupler operating at 2.4/3.5 GHz is designed for verification. The size of the BLC is about $0.025,lambda _{g^{2}},$ reduced by 92% compared with the conventional hybrid.