A broadband waveguide-to-microstrip transition/power splitter, using a finline array for waveguide mode termination and then transferring the energy to microstrip lines with a broadband slot-to-microstrip transition, is presented. A single back-to-back and four-element transition covering the X-band were designed, fabricated, and tested. Adapting the concept of microstrip-slot pulse inverter, another two-element array is also fabricated with wideband 180° out-of-phase outputs. The effects of the waveguide grooves for mounting the substrate are also investigated. By using multiple finline tapers on one substrate, the proposed structure can be employed in spatial power combining/dividing applications.
