A frequency scanning radar system includes a controller for controlling a frequency generator and a signal processor arranged to determine a Doppler frequency associated with a target. The frequency generator generates three or more sets of signals, each set of signals having a different characteristic frequency and including signals transmitted at a selected rate, and the radar controller selects the rate in substantially direct proportion to the characteristic frequency, whereby to normalize the Doppler frequency determined by the signal processor, such that the normalized Doppler frequency is substantially constant in relation to variation in the carrier frequency. In a frequency modulated radar system, each set of signals includes a sequence of modulation patterns, and the radar controller modifies a given modulation pattern in dependence on the characteristic frequency of the signal being modulated.