Bandwidth enhancement on waveguide transition to conductor backed CPW with high dielectric constant substrate

This paper proposes a broadband transition design between conductor-backed coplanar waveguide (CB-CPW) and rectangular waveguide based on the concept of the multisection transformer. The genetic algorithm (GA) was adopted to efficiently optimize the multisection transformer for achieving wideband performance. Using a multisection of order 3, a V-band transition realized on an Al₂O₃ substrate could achieve 25% bandwidth with a return loss better than 20 dB. Two transitions connected back to back were realized to demonstrate the feasibility of the transition. Also, a tolerance analysis was performed via the simulation to verify the robustness of this transition design.