Tightly coupling LTCC microwave coupled lines: analysis, modeling and realization

This paper presents the analysis and modeling techniques of broad side coupling structures fabricated with LTCC technique. By applying multi-conductor C-matrix and L-matrix extraction techniques to model small segment of two conductors vertically stacked on different layers of LTCC substrate, informations for designing a coupler were obtained. Knowing the C-matrix and L-matrix and their corresponding physical structure, we could synthesize the couplers of designated electrical properties. Applying the modeling and analysis techniques, the microwave tight coupling asymmetrical coupled lines were designed and realized with LTCC technique. The coupler could be tightly coupling with coefficient better than 3dB, isolation better than 35dB and about 40 dB directivity.