The design of broadband 3D Si-based directional couplers for millimeter-wave/THz applications

Wideband directional couplers with high isolation are designed for millimeter-wave applications and implemented in two different in-house Si-based technologies processes - Si-benzocyclobutene (Si-BCB) process and LIGA-like process (lithography, electroplating, and molding). Two 3D tandem directional couplers for millimeter-wave/THz applications have been constructed using the Si-BCB process. The coupling and isolation of tandem coupler have been analyzed from circuit topology. A branch-line coupler is also constructed using the LIGA-like process. The electrical characteristics of these couplers have been simulated in 3D simulator. By comparing the results, the proposed Si-BCB process is noted to provide flexibilities in both the design and implementation of passive components.