Wideband SIW-to-Planar Transitions for Thick-Thin Substrate Integration

Extensive work has demonstrated broadband, low-reflection transitions between substrate-integrated waveguide (SIW) and other planar lines, including microstrip, coplanar waveguide (both regular and conductor-backed/grounded), coplanar stripline, and slotline. When interfacing dissimilar stackups — for example, handing off from a thick substrate to a thin one — multilayer and vertical transition schemes are employed to preserve impedance continuity and suppress parasitic modes. These transitions have been validated through full-wave simulation and measurements across microwave and mm-wave bands, enabling dense, system-level integration of SIW with conventional planar circuitry.