Novel broadband planar balun using multiple coupled lines

This study presents a novel broadband planar balun using multiple coupled lines, which are realized easily in thick-multi-layer structures, to improve broadband characteristics compared with the conventional planar Marchand balun. Additionally, an extra shunt capacitor is added to compensate the output amplitude and phase imbalances due to inductive grounding-vias. This balun is fabricated by LTCC (low temperature co-fired ceramic) technology and miniaturized successfully to 3.2 mm x 2.5 mm x 1 mm for UWB applications (3.1-8.0 GHz). Finally, the measured results agree well with the electromagnetic (EM) simulated responses.