Patent ID: 8081105

Claim:
A method for measuring a radial velocity of a target with a radar, within a maximum range R max , comprising the steps of: transmitting an Orthogonal Frequency Division Multiplexing (OFDM) waveform p, the waveform comprising: N frequency carrier signals (p m ) mε{0, . . . , N−1} transmitted simultaneously, where N≧2, the frequency carrier signals (p m ) mε{0, . . . , N−1} coded in order to improve a Doppler response; and a plurality of OFDM chips and guard time intervals that are transmitted successively, on at least a portion of the N frequency carrier signals, to form a continuous wave transmission, wherein: a duration T cyc of the guard time intervals is longer than 2 ⁢ R max c , which is a time necessary for the waveform p to be reflected from a maximum range of interest R max , where c is a speed of light; receiving an echoed waveform from the target, to produce a received echoed waveform; recovering an initial phase φ m of each frequency carrier signal p m from the received echoed waveform, to produce a recovered initial phase φ m ; cyclically shifting the recovered initial phase φ m of each frequency carrier signal p m by a cyclic shift in order to compensate for a Doppler effect, to produce a recovered and shifted initial phase φ m ; decoding the recovered and shifted initial phase φ m of each frequency carrier signal p m , to produce a plurality of decoded initial phases (φ m ) mε{0, . . . , N−1} ; synthesizing a compressed pulse from the plurality of decoded initial phases (φ m ) mε{0, . . . , N−1} ; wherein the step of recovering the initial phase φ m of each frequency carrier signal p m from the echoed waveform further comprises a step of multiplying a vector s, containing samples of the echoed waveform, by a Discrete Fourier Transform matrix ℑ wherein the step of cyclically shifting the recovered initial phase φ m of each frequency carrier signal p m , further comprises a step of multiplying the recovered initial phase φ m by a matrix C −1 , wherein the matrix C −1 is an inverse of a matrix C that represents a shift of the frequency carrier signals (p m ) mε{0, . . . , N−1} due to the Doppler effect; wherein the step of decoding the recovered and shifted initial phase φ m of each frequency carrier signal p m further comprises a step of multiplying the recovered and shifted initial phase φ m by a matrix P=diag{φ*} where φ T =[φ 0 φ 1 φ 2 . . . N−1]; and wherein the step of synthesizing the compressed pulse from the plurality of decoded initial phases further comprises multiplying the plurality of decoded initial phases by a matrix ℑ −1 , wherein the matrix ℑ −1 is an inverse of the matrix ℑ wherein the recovered initial phases φ m of each frequency carrier signal p m is cyclically shifted so as to cover substantially all velocities of interest, to generate Doppler profiles to cover the velocity range corresponding to the cyclic shift.