PURPOSE: To use one frequency for the radar observation and also for the transmission of the necessary air traffic control data and improve the convenience.

CONSTITUTION: An air traffic control host computer 2 displays the received data of the position, range, and speed of an acquired aircraft P on a radar scope. The air traffic control host computer 2 transmits the data required for air traffic control to a ground radar transmitter/receiver 1, the data are inputted to a PCM modulator 12 through a reception I/F section 10 to apply pulse modulation to the oscillation signal from a radar wave signal oscillator 11, and the modulated signal is power-amplified by a radar transmitter 13 and transmitted through a circulator 4 and a beam antenna 4. The received signal from the antenna 20 of the aircraft P is processed by a receiver 21, it is demodulated by a PCM demodulator 22, the air traffic control data are sent to an air traffic control computer 24 through a transmission I/F section 23, and computer processing is implemented based on the air traffic control data.