A signal filtering method for filtering a numerical input signal that is sampled at a sampling frequency in order to obtain a filtered signal, the method including a first operation of application of a discrete Fourier transform to M points on a processed signal in order to obtain M points of the spectrum of the processed signal, each point of the spectrum of the processed signal corresponding to the even-numbered indices of a spectral analysis at 2*M points of the processed signal; and a second operation of application of a discrete Fourier transform to M points on the processed signal in order to obtain M points of the spectrum of the processed signal, each point of the spectrum of the processed signal corresponding to the odd-numbered indices of a spectral analysis at 2*M points of the processed signal.