Planar Transitions from Substrate Integrated Coaxial Line to Single-Layer Transmission Lines and Waveguides

This paper presents inline transitions from substrate integrated coaxial line (SICL) to microstrip line, coplanar waveguide (CPW), as well as substrate integrated waveguide (SIW). A common property is the conversion of transmission medium from double to single substrate layer of PCB. The first two of described transitions can be used from DC up to the presence of higher order modes if the characteristic impedances of two meeting transmission lines are matched. The transition to substrate integrated waveguide is of higher complexity, yet compact. Both sides of the SICL-SIW transition are strongly coupled to resonant cavity, and return loss greater than 20 dB is achieved in fractional bandwidth of 10.91 %. Improvements compared to the existing solutions have been made in designs of all three transitions.