Modeling, Design, Fabrication, and Performance of Rectangular μ-Coaxial Lines and Components

A miniature non-uniform copper-air rectangular coaxial line with the inner conductor supported by periodic dielectric straps is demonstrated. The overall height of the line is 310mum with the outer conductor cross-section being 250mumtimes250mum. The measured loss is 0.22dB/cm at 26GHz, while the isolation between two parallel lines with a center-to-center separation of 700mum is better than 60dB. Several quasi-planar components are designed and fabricated on the same wafer, and presented here are a branch-line hybrid and a transmission line resonator. The through and coupled port transmissions for the hybrid at 26GHz are -3.25dB and -3.35dB respectively, with phase misbalance below 0.2deg. The transmission line resonator has an unloaded Q-factor of 110 at 25GHz