Broadband Connection of SIWs in Different Layers Using Back-Short Structures and Patch Element in 270-GHz Band

In this study, a broadband connection of substrate-integrated waveguides (SIWs) in different layers using a back-short structure and patch element for the 270-GHz band has been proposed. The broadband operation combined techniques, including coupled patch, aperture coupling, and a back-short structure. The transition principle was investigated through parameter studies conducted via electromagnetic simulations using the finite element method. The transition design was observed to be successful within fabrication limitations in the subterahertz band. Simulations of the connection of SIWs in different layers gave a reflection coefficient bandwidth of less than −10 dB at 73.8 GHz, with a transmission coefficient of −0.7 dB at the center frequency of 270 GHz. A waveguide (WG)-to-SIW-to-SIW transition with a back-to-back configuration was designed, fabricated, and measured in the subterahertz band. The measured transmission coefficient for a single multilayer WG-to-SIW-to-SIW transition was −1.8 dB at 270 GHz. The measured results revealed a reflection coefficient bandwidth below −10 dB of 64.0 GHz (22.8%), spanning from 248.0 to 312.0 GHz.