PURPOSE: To maintain the stable tracking of a target, by securing the automatic switching to the normal trackig in case the MTI tracking is impossible by giving the by-passing to the MTI process according to the result of measurement of the Doppler frequency.

CONSTITUTION: The video signal given from a receiver 15 is fed to a distance tracking device 17 and an angle tracking device 18 respectively after an MTI process. Then the differential component of the distance data given from the device 17, the Doppler filter group or the combination of both is sent to a speed measuring device 20. In case the MTI tracking is judged impossible, the MTI process is by-passed. When the MTI tracking is possible, the MTI process is carried out. At the same time, the period of the optimum pulse is selected for a stagger pulse train by a transmission pulse selection signal to be fed to a transmitter 12 from a modulator 11. In such way, the switching is automatically carried out to the normal tracking in case the MTI tracking is impossible. Thus the stable tracking is maintained for a target.