Design of wideband LC balun embedded into organic substrate using coupled LC resonators

In this paper, wideband LC balun using coupled LC resonator has been designed, simulated and fabricated for being embedded into an organic packaging substrate. The proposed balun has a novel scheme which consists of two pair of coupled embedded LC resonators which share one resonator with each other. The coupled resonators are applied to obtain a precise phase difference of 180 degree and an identical magnitude between two balanced ports. This proposed balun has relatively small inductance and capacitance values which can be easily embedded into the organic packaging substrate. The capacitors at embedded LC resonators were realized by using high dielectric BTO composite film. The measured result shows that fabricated balun has excellent phase and magnitude imbalanced characteristic. The measured results are an insertion loss of 1.8 dB, a return loss of 10 dB, a phase imbalance of 0.5 degree and magnitude imbalance of 0.7 dB at frequency bandwidth of 700 MHz ranged from 1.8 GHz to 2.5 GHz, respectively. The fabricated balun has a volume of 2 mm x 3.5 mm x 0.66 mm (height). The measured result was well agreed with the simulated results.