A heart-rate sensor for detecting artery blood-flow volume per unit length change in a human or animal subject, which comprises an antenna for sensing the instantaneous volume of blood in the artery of the subject, to be measured a RADAR unit for transmitting microwave signals into a subjects body part or limb representing tissue targets. The output of the RADAR unit includes a superposition of signals each of which corresponding to a different tissue target with amplitudes that relate to the targets reflection strength a sampling circuitry for converting reflected signals to digital a window function circuitry for suppressing unwanted spectral sidebands originating from the subsequent processor operating on time truncated data an FFT processor following the window function circuitry, for splitting the superposition according to its relative frequency into a multiplicity of bins, each of which with an amplitude that represents the reflection magnitude of a target at a specific distance from the antenna a signal processor for filtering out the effect of the sensor movement with respect to the subject body part, or the movement of the body part, and for generating a signal, the amplitude of which is proportional to the artery varying dilatation representing the heart-rate a heart-rate estimator for measuring the frequency of the artery dilatation variations and for canceling the interference of the amplitude of any signal that does not originate from the artery a battery for powering the sensor.
