PURPOSE: To increase the effective length of an antenna by setting the element antennas even at inapplicable places and distributing the electronic power to plural antennas from active modules set at places where the element antennas are thinned.

CONSTITUTION: Active modules b1∼bn are connected to element antennas a1∼ an respectively. A phase shifter is provided together with a high output amplifier, a low noise amplifier and a transmission/reception switch. An electronic power distribution synthesizer (c) supplies and synthesizes the reception signals of antennas a1∼an via active modules b1∼bn. Then active modules B1∼BN which perform no transmission/reception owing to thinning are used to distribute the electric power to element antennas A1∼AN set at the positions where the physical distribution of active modules is impossible via feeders l1∼lN. Thus the effective diameter of the antenna is increased.