Method of and device for detecting the presence of a living being of a particular species in a space monitored by a doppler sensor

DETAILED DESCRIPTION This aim is achieved by a method of detecting the presence of a living being of a particular species, in particular a human being, in a monitored space in which there is disposed a microwave Doppler sensor supplying a low-frequency signal produced by beating between a transmitted wave and reflected wave, frequency shifted by the Doppler-Fizeau effect by a moving target in the monitored space, wherein the signal, after any necessary amplification and filtering, is digitized and processed to show up in the frequency spectrum of the signal from the sensor peculiarities specific to the species of the living being in order to recognize the presence of a being of that species, characterized in that the processing of the digitized signal comprises the following steps: a) determining the overall energy of the digitized signal and eliminating signals with energy less than a threshold energy; b) applying to the signal produced by step (a) at least one autocorrelation test adapted to detect the presence of a dominant frequency; c) filtering the digitized signal by means of an adaptive filter adjusted to reject the dominant frequency detected in step (b); d) determining the global energy of the signal produced by the filtering step (c) and eliminating the signals having energy less than a threshold energy; e) filtering the signal from step (d) to isolate a particular frequency band that is stable and specific to movements of the particular species of the living being; f) applying to the signal from step (e) a test of temporal intercorrelation with a reference signal specific to the particular species of living beings and held in memory to define an interspectral energy and sending of at least one two-state signal corresponding to interspectral energies respectively greater than and less than a threshold energy.
A study of the signatures of the interference phenomena mentioned above has shown that some of these phenomena have a marked periodic character and that their signatures consist in one or more characteristic frequencies that have a dominant presence in the signal from the Doppler sensor