Compact Ultra-Wideband Microstrip 3dB Branch-Line Coupler Using Coupled-Lines

In this paper, a compact wide band microstrip 3dB branch-line coupler (BLC) is presented for wider operation band and size reduction. The proposed BLC is composed of single coupled-lines, and cascaded two sections in structure, which gives the broad operation band, good impedance matching, and the excellent isolation. By comparing with conventional microstrip 3dB BLC, the proposed hybrid coupler has 52% size reduction at the frequency band of 1.5~3.0GHz. As well as it gives more than 4% operation bandwidth increased for reflection and isolation performance.