Millimeter-Wave Topside Waveguide-to-Microstrip Transition in Multilayer Substrate

A topside waveguide-to-microstrip transition whose waveguide sits on the top of the substrate was developed in the millimeter-wave band. A double-layer substrate was attached at the WR-10 waveguide end. A coupling patch is located on the top surface with spacing of the upper substrate thickness from the microstrip signal line patterned between the upper and the lower substrates. The transmission characteristics of the transition are controlled by the dimensions of the coupling patch and the insertion length of the microstrip signal line into the waveguide. All the dimensions of the transition were optimized by electromagnetic analysis of the finite-element method at 76.5 GHz. The feasibility was confirmed by experiments in this letter.