A method includes: generating a frequency-modulated continuous signal, an emission sequence being formed of successive ramps centered on a carrier frequency; fixing a modulation band ΔF and the duration Tr of a recurrence in such a way that at the range limit, a reception ramp appears shifted by at least one given frequency with respect to the corresponding emission ramp, on account of the propagation delay for the outward-return journey to a target kTr+θ, k being an integer and θ a duration less than Tr; demodulating the signal received by the signal emitted, the resulting signal including a first sinusoid at the frequency δFdim=(1−(θ/Tr)·ΔF and a second sinusoid at the frequency δFd=(θ/Tr)·ΔF; sampling the resulting signal and performing a first fast Fourier transformation on this resulting signal over the duration of each emission ramp; detecting in the resulting spectrum the spectral lines appearing at the frequencies δFd and δFdim, and performing the vector sum of these two spectral lines after resetting them into phase with respect to one another; and performing a detection by comparing the modulus of the vector sum with a predetermined threshold.