PURPOSE: To enable the substantially complete removal of the transmission and reception of signals by a side lobe of an antenna, by a method wherein a vertical beam emitted from an SLS antenna is directed below the direction of a vertical beam emitted from an INT antenna.

CONSTITUTION: A rectangular INT antenna 1 constructed of a plurality of elements 1A... arranged at prescribed intervals in one line and shaped in the same slender rectangle substantially, and an SLS antenna 2 formed of an element positioned in the central part of said antenna, are provided. Out of these antennas, the antenna 2 is so installed as to be directed slightly below a plane formed by the elements 1A.... Therefore a vertical beam emitted from the antenna 2 is directed slightly below the direction of a vertical beam emitted from the antenna 1. By this constitution, the gain of the antenna 2 at a low angle of elevation is increased. Consequently, a gain difference between the antenna 1 and the antenna 2 at the low angle of elevation is reduced.