A Wideband Transition From Coaxial Line to Substrate-Integrated Waveguide

This article presents a novel broadband transition from coaxial line to substrate-integrated waveguide (SIW). The SIW wall includes three rows of metallic vias, where the vias of smaller diameter are squeezed between vias of larger diameter. This modification results in a corrugated via-wall SIW (CVWSIW) providing lower loss. Three versions of stubs (rectangular, semicircular, and triangular) are designed around the coaxial line launch on the top metal plane of the SIW. All transition versions are fabricated and tested, and the measurement results are in a good agreement with simulations. The measured more than 14-dB return loss (RL) and fractional bandwidth (FBW) of 75%, 79.4%, and 44.6% (10-dB FBW: 97.14%, 90.5%, and 78.26%) in these versions for the 9–26-GHz frequency range were obtained, respectively. The insertion loss (IL) is less than 0.63, 0.91, and 0.68 dB; the total loss is below 20%, 30%, and 25% for these versions for the same frequency band, respectively.