PURPOSE: To simplify the microwave shield structure by storing dielectric circuit boards for horizontally and vertically polarized waves in an enclosure integrated with a horn antenna and placing an input part waveguide between both dielectric circuit boards.

CONSTITUTION: The microwave inputted to a horn antenna 21 is transmitted to a waveguide and is inputted to a first dielectric circuit board 26 in the circuit storage space formed by a second enclosure 24 and a first enclosure 22 for shield. An antenna part pattern for one of horizontally and vertically polarized waves is provided on the surface of this circuit board 26, and one polarized wave of an input wave is inputted to the first dielectric circuit board 26. A waveguide 23 is coupled to the rear part of the circuit board 26 in such form that the waveguide 23 is interposed between the circuit board 26 and a second dielectric circuit board 27, and a short frame 28 is provided for the purpose of obtaining an input return loss most suitable for the waveguide-micro strip line and a small conversion loss. The other polarized wave is inputted to the second dielectric circuit board 27 in the same manner and is converted to the waveguide micro strip line.