MOVING TARGET INDICATION SYSTEM

In order that it should respond satisfactorily to substantially all moving targets within range (without exhibiting "blind speeds") and ignore all stationary targets, a moving target indication system comprises an FM continuous wave radar system in the form of an oscillator (1) the output frequency of which is swept by the output signal of a triangular-wave generator (19). The oscillator output signal is fed to an aerial (3) via a circulator (4) and also to a first input (6) of a mixer (7) a second input (8) of which is supplied with the return signal from the aerial. The respective output waveforms of the mixer occurring for sweeps of the oscillator frequency in the two senses, are, in a further circuit (11), subtracted one from the other after effectively time-reversing one of them, and the resulting difference waveform is analysed in a Fast Fourier Transform calculating circuit (15). The triangular-wave generator (19) may be replaced by a sawtooth-wave generator, in which case the effective time-reversal in the further circuit (11) should be omitted.