Method and apparatus for transmitting a continuous radar wave

The radar generates a base signal S1 which is mixed with a frequency ramp S2 to produce a signal S3 having two spectral components whose frequency ramps are symmetrical mirrors of each other. Instead of filtering one of these sidebands out, both are used. The dual frequency signal S3 is mixed with a carrier signal S4 and transmitted. A receiver 230 down-converts 233 the received signal, filters 241 it into its frequency components, mixes it with the dual frequency signal S3, filters 243 a component and digitises 245 this. A triangular waveform may result in the two components crossing over each other (Fig. 5C). A plurality of such pairs of frequencies, each centred on a different central frequency, may be used (Fig. 7A, 8A, 8B).