PURPOSE: To provide cosecant square characteristics in a vertical plane and nondirectivity in a horizontal plane by providing a main reflector in a nearly comic or frustum-of-circular-cone shape and a primary radiator which excites this main reflector for communications between a center station and many peripheral slave stations.

CONSTITUTION: A necessary mode is generated by a mode generator 14 with an electromagnetic wave sent out of a transmitter receiver 16 through a waveguide 15 and the primary radiator 13 is excited, so that the radio wave is reflected by the reflecting surface 12 of a conic rotary double curve reflector (main reflector) 11 and radiated in a horizontal plane. For reception, this system operates reversibly to the transmission. The mirror surface shape of the antenna which has almost cosecant double characteristics in the vertical plane and pencil beam characteristics in the horizontal plane is known as the double curve reflecting mirror, whose center sectional shape 17 consists of two curves a1 and a2 differing in directivity direction. This main reflector 11 is formed by rotating this sectional shape 17 around an axis 18 of rotation and the primary radiator 13 is installed at the focus of the main reflector 11.