Patent ID: 7368692

Claim:
A microwave applicator comprising: a source of microwave energy; a serpentine waveguide coupled to the source of microwave energy and having: an array of waveguide passes having a pair of opposite first sides lying in first parallel planes and pair of opposite second sides lying in second parallel planes perpendicular to the first parallel planes bounding an interior having a rectangular cross section with four corners, wherein the opposite first sides include slots and the array of waveguide passes are disposed side by side with the slots aligned to admit a material to be exposed to microwave energy into the waveguide passes; waveguide bends connecting the waveguide passes in series so that microwave energy flows in opposite directions in consecutive waveguide passes; tunnels disposed between facing first sides of consecutive waveguide passes to enclose the material to be exposed as the material advances through the facing slots in the first sides of the consecutive waveguide passes; wherein the waveguide passes include conductive ridges projecting into the interior of the first and second planes at the four corners of the rectangular cross section to reduce the microwave energy at the slots in the waveguide passes.