DOI: 10.1109/TMTT.2025.3587087   IEEEXplore: https://ieeexplore.ieee.org/document/11079808    

Two-mode, single-layer coaxial-to-substrate integrated waveguide (SIW) transition.

6.0 - 7.7 GHz (1st mode); 10.1 - 10.74 GHz (2nd mode)

The coaxial feed that excites the fundamental mode is located in proximity to a reactive load instead of a short-circuit. The feed is not located in the proximity of a terminal wall, but is located in front of a row of metal vias placed in the middle of the SIW, which create two parallel SIW interconnects that are below cutoff in the single-mode band of the SIW. The number of metal vias in the middle of the SIW has been chosen to ensure isolation between ports better than 20 dB in simulation over the entire operation band where the transition of the second SIW mode has been optimized. The coaxial feed passes through the substrate, and the inner conductor is soldered to the bottom metal plate for cost-effective manufacturability.

Microwave components with SIW structures where it is useful to launch the SIW fundamental mode and second mode independently, characterize both the fundamental mode and second mode simultaneously, and to determine the possible mode conversion in the structure.

>15 dB input matching from 6.021 to 7.727 GHZ (1.706 GHz BW), 34.12% FBW, < 0.88 dB IL for the fundamental SIW mode launcher; >15 dB input matching from 10.072 to 10.735 GHz (0.663 GHz BW), 13.26% FBW, <1.25 dB IL for the second SIW mode launcher.