A Wideband Transition from Coaxial Line to Substrate Integrated Waveguide

This paper presents a novel broadband transition from coaxial line to substrate integrated waveguide (SIW). The transition, in three versions reflecting the attempt to improve the bandwidth, is designed for 8 to 26 GHz frequency range. Two metallic via rows are placed in parallel with the first row of metallic vias. This modification results in a corrugated wall SIW (CWSIW) providing lower loss for all versions. Three different stubs (rectangular, semicircular and triangular) are placed around the coaxial line attachment on the top metal plane of the SIW. The transitions are fabricated and tested, and the measurement results are found in good agreement with simulations. The measured 15 dB return loss (RL), fractional bandwidth (FBW) of 75, 79.4, and 44.6% in these versions at the 9.5-22 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, 25% for these versions at the same frequency range, respectively.