A method for detecting a plurality of useful signals in a total signal. The useful signals correspond to radiofrequency signals emitted by different terminals in a multiplexing frequency band. A plurality of spectrograms calculated that have a compensated linear frequency drift and are respectively associated with different linear frequency drift values. For each analysis frequency and each spectrogram, time envelope filtering of the values is performed at the different times for analyzing the spectrogram at the analysis frequency using a filter representing a reference time envelope of the useful signals. A useful signal is detected at an analysis time and at an analysis frequency in response to a verification of a predefined detection criterion by the value from a spectrogram resulting from filtering at the analysis time and at the analysis frequency.