A frequency down converter. A plate body of the frequency down converter includes a main surface. A first wave guide includes a first section and a second section connected to the first section. The first section is connected to the main surface and extends parallel thereto. The second section extends perpendicular to the main surface. A second wave guide includes a third section and a fourth section connected to the third section. The third section is connected to the main surface and extends parallel thereto. The fourth section extends perpendicular to the main surface.