Measurement of instantaneous heart rate using radar echoes from the human head

The feasibility of measuring heart rate using radar echoes from a human head is demonstrated. Non-contact measurement of vital signs using radar has been attracting much attention because such technologies can breakthrough benefits for monitoring health conditions without electrodes or wearable devices. Most existing studies have measured echoes from the torso, particularly the chest wall. However, this is difficult because of multiple interfering reflections from the complex shape of the torso and other body parts, such as limbs. The current study is the first demonstration that non-contact heart rate measurement can be easily achieved using echoes from the human head. There are two important advantages of measurement from the human head: (i) the simple shape of the head makes an ideal radar target with only a single reflection, and (ii) the other undesired echoes can be removed using time-gating when an ultra-wideband radar is used. Nonetheless, because the displacement of the human head due to heart rate is small, a millimetre-wave ultra-wideband array radar system is developed, which is installed on the ceiling and used in the proposed measurements with participants.