A device having an upper plate comprising a top face and a bottom face with an opening. A lower plate comprising a top face and a bottom face substantially parallel to the upper plate, with an opening. A middle plate between and substantially parallel to the upper plate and lower plate, capable of moving with respect to the upper plate and lower plate, and having a top face a bottom face and at least one opening. A plurality of gaskets configured to electrically connect the upper plate, the middle, plate, and the lower plate and provide an interface that is designed to allow the middle plate to slide substantially parallel to the upper plate and the lower plate. At least one waveguide through the at least one opening of the middle plate.