PURPOSE: To eliminate an undesired radiation wave and to improve the wide angle radiation characteristic by mounting a radio wave absorbing body of a curved face forming a torus group over the radio channel of an antenna system.

CONSTITUTION: The radio wave absorbing body 5 having a curved face whose cut face perpendicular to the beam axis form a torus group is fit along the peripheral of the beam in a zone where a beam radiated from a feeding horn 4 is radiated from the aperture of a main reflecting mirror 1. Thus, a refracted wave contributing to an undesired radiation from an edge A1 of a focus reflecting mirror 3, an edge B1 of a sub reflecting mirror 2 and an edge C1 of a main reflection mirror 1 is eliminated by using the radio wave absorbing body 5. Thus, the wide angle radiation characteristic of the antenna system is improved.