PURPOSE: To make it possible to compensate the shift of an echo signal relative to a trigger signal, by delaying the echo signal treated and outputted corresponding to an electric wave only in phase difference counted by a clock pulse.

CONSTITUTION: An electric wave emitted from a radar apparatus 1 is sent out in synchronous relation to a trigger signal which is, in turn, inputted to a synchronous circuit 3 and supplied to a processing unit 5 as the trigger signal in synchronous relation to a reference clock outputted from the apparatus 5. By this mechanism, the false echo signal generator of the apparatus 5 is operated and an echo signal is applied to a delay circuit 6 as the distance reference of the echo signal. In addition, the trigger signal at the emission time of the electric wave is detected with respect to the phase difference with the reference clock from the apparatus 5 in a detection circuit 7 and the detected data is applied to the circuit 6 as thedelay data. The circuit 6 successively shifts the echo signal corresponding to the value of the delay data by an original oscillating clock to issue the echo signal. This compensated echo signal is displayed by a PPI scope 8 and the desired position of a flight body is calculated.