Patent ID: 7180580

Claim:
A method for producing, in a receiver, observable frequency shifts δω indicative of the distance r to a target at one or more frequencies ω in propagating waves emitted, reflected, transmitted or scattered by the target, wherein the receiver includes a variable frontend means to select or influence the selection of frequencies or wavelengths and a shift detector means to measure the frequency shifts from the output of the frontend means, the method comprising the step of varying the instantaneous selection of frequencies or wavelengths by the frontend means at a known or predetermined normalized rate β, in order to scan the phases φ({circumflex over (k)}) of successively selected frequencies {circumflex over (k)} at the instantaneous rates d{circumflex over (k)}/dt={circumflex over (k)}β, thereby inducing in its output the shifts δω in proportion to the distance r from the path contributions {circumflex over (k)}·r contained in φ({circumflex over (k)}) as δω=∂φ/∂t| r =∂({circumflex over (k)}r)/∂{circumflex over (k)}·d{circumflex over (k)}/dt=r·{circumflex over (k)}β.