Embodiments described herein provide a microwave coupler that utilizes a microwave shield within an interior of the microwave coupler to mitigate Radio Frequency (RF) leakage from an end of the microwave coupler. The microwave coupler includes a ramp section that is configured to mate to a microwave source, with the ramp section extending from an opening in a top wall of an enclosure. One end of the enclosure is configured to mate to a microwave waveguide, while an opposing end may be open or partially open. The microwave shield is located between the opposing end of the enclosure and the opening in the top wall, and extends from the top wall of the enclosure towards a bottom wall of the enclosure.