A Novel Compact LC-Based Balun Combiner with 2nd and 3rd Harmonic Suppression

Abstract

This paper presents a novel compact balun combiner based on lumped inductors and capacitors. In addition to the functions of harmonic reducing, power combining, and impedance matching, the new structure accomplishes both the 2nd and the 3rd harmonic suppression by constructing band-stop filters and cancellation pathways. The proposed topology is studied theoretically and demonstrated on an FR4 printed circuit board with the size of 2 cm×4 cm. Experiment results show that differential power combination is achieved with around 0.7-dB loss for each path when all three ports are loaded to 50 ohms at 1 GHz. The 2nd harmonic suppression is more than 28-dB at 2 GHz and the 3rd harmonic can be largely canceled out with equal amplitudes while opposite phase at 3 GHz. Furthermore, the topology can be applied in not only printed circuit boards but also monolithic microwave integrated circuits.