Method for demodulating a received signal, the said received signal resulting from the modulation of a basic chirp signal whose instantaneous frequency (102, 102', 102", 102"') varies linearly between a first instantaneous frequency f0 and a second instantaneous frequency f1 during a symbol time Ts, the said modulation corresponding, for a symbol of rank s of a constellation of N symbols, s being an integer from 0 to N-1, to a circular permutation of the variation pattern of the said instantaneous frequency on the said symbol time Ts, obtained by a time shift of s times an elementary time duration Tc, such that N ∗ Tc=Ts, and the transmission of the modulated chirp signal in a transmission channel, characterised in that it comprises an estimate step of a symbol carried by the said received signal, implementing the following sub-steps, for N samples of the said received signal and for N samples of a reference chirp signal obtained by modulating the said basic chirp signal by a reference symbol corresponding to a symbol of rank r in the said constellation, taken at the same multiple times of Tc: - conjugation of the said N samples of the said reference chirp signal, respectively of the said N samples of the said received signal, delivering N samples of a conjugated chirp signal; - multiplication term by term of the said N samples of the said conjugated chirp signal by the said N samples of the said received signal, respectively of the said reference chirp signal, delivering N samples of a multiplied signal; - direct or inverse Fourier transformation of the said multiplied signal, delivering N samples Y l of a transformed signal, where I is an integer ranging from 0 to N-1; - determination of N decision components, from the said N samples Y l of the transformed signal, a decision component of index I, denoted as component D l, being a function of a term whose phase depends quadratically on I, where I is an integer from 0 to N-1; - decision of rank k of the symbol carried by the said signal received, from the decision component of index k denoted as component D k, having an extreme value among the said N decision components, the said component D k being furthermore a function of a term proportional to an amplitude of the sample of the said index k, Y k, among the said N samples Y k of the said transformed signal, as well as of the phase of the said sample Y k. - conjugation of the said N samples of the said reference chirp signal, respectively of the said N samples of the said received signal, delivering N samples of a conjugated chirp signal; - multiplication term by term of the said N samples of the said conjugated chirp signal by the said N samples of the said received signal, respectively of the said reference chirp signal, delivering N samples of a multiplied signal; - direct or inverse Fourier transformation of the said multiplied signal, delivering N samples Y l of a transformed signal, where I is an integer ranging from 0 to N-1; - determination of N decision components, from the said N samples Y l of the transformed signal, a decision component of index I, denoted as component D l, being a function of a term whose phase depends quadratically on I, where I is an integer from 0 to N-1; - decision of rank k of the symbol carried by the said signal received, from the decision component of index k denoted as component D k, having an extreme value among the said N decision components,